31st International Seminar on Interaction of Neutrons with Nuclei: Fundamental Interactions & Neutrons, Nuclear Structure, Ultracold Neutrons, Related Topics (ISINN-31)

25 May 2025, 09:00 → 30 May 2025, 15:00 Asia/Shanghai

Exhibition International Hotel, Dongguan

Dongwei Hei (黑东炜) (NINT) , Sheng Wang (王生) (CSNS) , Egor Lychgain (Joint Institute for Nuclear Research)

Foreword

The International Seminar on Interaction of Neutrons with Nuclei “Fundamental Interactions & Neutrons, Nuclear Structure, Ultracold Neutrons, Related Topics” (ISINN) was initiated by the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research in 1993. ISINN continues the tradition of FLNP annual workshops and seminars in this area. The aim of such a seminar is to provide a forum for scientists and engineers to present their achievements, exchange ideas and promote potential cooperation.

The last seminar was organized both online and in person in Sharm El-Sheikh, Egypt. The ISINN-30 made it possible to bring together participants from many countries and was very successful and fruitful. The joint Organizing Committee that comprises representatives from the Frank Laboratory of Neutron Physics, China Spallation Neutron Source Science Center and State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, warmly welcomes scientists from all over the world to join us in Dongguan, China, from May 26 to 30, 2025.

The working language of the Seminar is ENGLISH.

Topics

• Fundamental properties of  the neutron
• Fundamental interactions & symmetries in neutron induced reactions
• Properties of compound states, nuclear structure
• Intermediate and fast neutron induced reactions
• Nuclear fission
• Nuclear data for applied and scientific purposes
• Neutron detection & Methodical aspects
• Physics of ultracold neutrons
• Nuclear and related analytical techniques in environmental and materials science
• ADS studies
• Neutron radiation effects
• Nuclear reactor physics
• Radiation transportation and simulation
• Advanced neutron sources and perspective experiments

Programe Arrangement

There will be five types of presentations during the seminar:

• keynote speeches
• plenary talks
• invited talks
• oral contributions
• posters

Keynote speakers will be invited only by the Organizing Committee, while plenary and invited talks will be selected from the abstract pool through internal review.

Organizers

• Frank Laboratory of Neutron Physics, JINR, Dubna

• China Spallation Neutron Source Science Center, IHEP, CAS, China

• State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, NINT, China

Sponsors & Exhibitors

Sponsorship from nuclear related enterprises is welcome, and ISINN-31 will provide an excellent opportunity for companies to showcase their services, products and techniques. Potential sponsors or exhibitors are invited to contact us at isinn31@163.com for more details.

Contact

Official Website: 

https://isinn.jinr.int/

Email of Secretariats:

isinn@jinr.int

Seminar_Poster.png

会议通知（盖章）.pdf

Sunday, 25 May

Registration

Convener: Pengyu Sun (CSNS)

18:00 Welcome Cocktail Reception

Monday, 26 May

Plenary Session

Convener: Yuri Kopatch (Joint Institute for Nuclear Research)

1 Welcome Speech

2 The Status of CSNS

Speaker: Sheng Wang (CSNS)

CSNS_ISINN.pdf

3 Experimental Infrastructure of the Frank Laboratory of Neutron Physics for Research

The Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) is one of the leading centers for neutron physics in the JINR Member States. FLNP scientists conduct research in the fields of condensed matter physics and nuclear reactions with neutrons, as well as to solve a wide range of applied problems using nuclear physics techniques. The basic facility of the Laboratory is the unique periodic pulsed reactor IBR-2. Most modern research methods using neutron scattering are realized at neutron beams of the reactor, as well as neutron activation analysis and studies of radiation effects from neutrons and gamma-rays. FLNP has accumulated a significant amount of state-of-the-art laboratory equipment, which provides information, supplementary to neutron investigations, about the studied samples using various physical methods. This makes it possible to obtain comprehensive information about objects under study. The User Program implemented in the Laboratory provides a unique opportunity for scientists from all over the world to gain access to the research infrastructure of the IBR-2 reactor.
The source of resonance neutrons based on the IREN electron accelerator and the EG-5 electrostatic generator, as well as fast neutron generators, expand the range of possible studies with neutrons in both fundamental and applied research.
The report will provide information about the experimental infrastructure available at FLNP, including examples of research, as well as information on how to access the infrastructure through the User Program.

Speaker: Egor Lychgain (JINR)

10:30 Coffee Break and Photo

Plenary Session

Convener: Tianjiao Liang

4 Progress on Neutron-Induced Nuclear Fission

Speaker: Zhigang Ge (CIAE)

ISINN-31-GEZHIGANG.pdf

5 Experimental Study of Parity and Time-Reversal Symmetries in Polarized Epithermal Neutron Optics

The parity violating effects in nuclear interactions is extremely enhanced in resonant neutron absorption processes via compound nuclear states for some of medium-heavy nuclei. The enhancement is explained as a result of the interference between parity-unfavored partial amplitudes of the compound nuclear process, which is referred to as "s-p mixing". The "s-p mixing" is expected to enhance the visibility of the effect of the breaking of both parity and time-reversal symmetry (P-odd T-odd). Based on these considerations, an experimental approach to search for the P-odd T-odd effects to activate a novel type of new physics search beyond the standard model is in progress using the pulsed neutron beam from the pulsed spallation neutron source of Japan Proton Accelerator Research Complex (J-PARC) under the collaboration "Neutron Optical Parity and Time-Reversal Experiment (NOPTREX)" as the program number J-PARC E99. P-odd T-odd effects will be studied in neutron optics in which fake T-violating effects can be controlled, with the enhanced sensitivity biased to chromo-EDM. We discuss the studies of the "s-p mixing" in 139La(n,γ)140La and the plan of T-violation search with polarized lanthanum target.

Speaker: Hirohiko M. Shimizu (Nagoya University)

20250526.pdf

6 Recent Advances of the (n, cp) Reaction Measurements

Abstract: Nuclear data of the (n, cp) reactions are important in the development of nuclear energy, the application of nuclear technology and the research of nuclear reaction theory. Based on the neutron sources of the 4.5 MV Van de Graaff accelerator of Peking University, EG-5 Van de Graaff accelerator of JINR, FLNP, HI-13 tandem accelerator of CIAE, and the CSNS Back-n, we have extended our measurements of the (n, cp) reactions from solid samples to gas samples, from GIC to TPC, and from binary fissions to ternary fissions. Recent advances in these three aspects are illustrated.

Speaker: Guohui Zhang (Peking University)

12:30 Lunch

Plenary Session

Convener: Hirohiko M. Shimizu

7 Review of Recent Activities on the Tagged Neutron Method at FLNP JINR

The tagged neutron method (TNM) is currently being implemented at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, for neutron-nuclear physics research. This method utilizes the reaction d+t→α+n to produce neutrons with an energy of approximately 14 MeV, which are emitted simultaneously with α-particles in nearly opposite directions. Neutron tagging is achieved through detecting the associated α-particles. The ING-27 neutron generator, equipped with a built-in position-sensitive α-particle detector consisting of 9, 64, or 256 pixels, serves as a source of tagged neutrons. These generators are manufactured by the Dukhov All-Russia Research Institute of Automatics (VNIIA).

The report will outline various experimental setups developed at FLNP for experiments involving tagged neutrons. It will also provide an overview of the results obtained, including the determination of differential cross-sections for elastic and inelastic neutron scattering on atomic nuclei, measurement of angular correlations between neutrons and gamma-rays, non-destructive elemental analysis utilizing the TNM, and its application for determining carbon content in soil.

Acknowledgment
The present study was supported by the Russian Science Foundation (RSCF grant No. 23-12-00239).

Speaker: Yuri Kopatch (Joint Institute for Nuclear Research)

kopatch_isinn31.pdf

kopatch_isinn31.pptx

8 Two-Wave Acceleration Effect and Ultra-Sensitive UCN Spectrometry

The Acceleration Effect (AE), the existence of which was recently predicted in [1], is a generalization of the previously discovered of optical Accelerating Matter Effect (AME) [2]. It consists in the fact that the result of the interaction of a wave with an accelerating object is a change in its frequency. The effect is proportional to the acceleration of the object and the time delay caused by this interaction. The existence of AE in macrophysics, for example, when transmitting a signal to an accelerating transceiver, is beyond doubt, since in this case it can be interpreted simply as a differential Doppler effect. The same interpretation is valid in the case of AME, when a wave passes through an accelerating layer of matter, experiencing Doppler frequency shifts of various magnitudes on the input and output surfaces of the sample. Verification of the validity of the AE concept in the quantum sector [3], when its relationship with the Doppler effect is not obvious, is still awaiting its experimental confirmation.
A special case of AE, which occurs when a wave passes through an accelerating sample of a birefringent substance, was considered in [4]. In neutron optics, the phenomenon of birefringence is usually associated with the different spin states of the two waves. The difference in the refractive index for these two waves leads to a difference in their propagation times in the sample and, as a result, to a difference in the magnitude of the frequency shift of these two waves passing through the accelerating sample. The interference of these two waves, which have changed frequencies by a different amount due to the AE, leads to periodic oscillations of the polarization of the resulting state, which can easily be transformed into oscillations of the counting rate. Thus, it is possible to register a very small difference in the energies of two spin states, and the sensitivity of the measurement increases with decreasing neutron energy. In the case of UCN, it is possible, in principle, to register the energy difference of two waves on the order of 10^(-15)eV.
The project of the UCN source currently under discussion at JINR makes it necessary to consider the two-wave Acceleration Effect as one of the important fields of research with this source. The report is devoted to discussing this possibility. The aim of future work will be to demonstrate the validity of EC in neutron scattering on quantum objects with a characteristic interaction time of the order of 10^(-7)s, as well as measurements of the spin-dependent neutron-nuclei scattering amplitudes. The high sensitivity of the method makes it possible to carry out such measurements with samples characterized by very low, up to 10-7, polarization of nuclei, because of which there is no need for a complex and expensive technique for preparing a polarized nuclear target.

[1] A.I. Frank. Physics-Uspekhi 53, 500 (2020).
[2] A.I. Frank, P. Geltenbort, M. Jentschel, et al. Phys. At. Nucl., 71 (2008) 1656
[3] M.A. Zakharov, G.V. Kulin and A.I.Frank. Eur. Phys. J. D 75, 47 (2021)
[4] A.I. Frank, V.A. Naumov. Phys. At. Nuc., 76 (2013), 1423

Speaker: Alexander Frank (Joint Institute for Nuclear research)

02Frank.pdf

9 Modeling the Neutron Whispering Gallery to Search for New Short Range Forces

New short-range forces (SRF) are predicted in many theories beyond the Standard Model of particle physics in the form of weakly interacting scalar or pseudo-scalar bosons. For example, dark matter could be explained by the existence of a weakly interacting boson, and some theories with extra spatial dimensions predict such a particle. Neutrons are useful tools in searches for these SRFs due to their neutrality and small electric polarizability. These properties minimize false effects in experimental searches for new interactions. Precision studies of the neutron whispering gallery effect, or the confinement of neutron matter waves along a smooth curved surface, is a particularly promising method to search for these new forces.

By sending a cold neutron beam with a grazing incidence angle into a cylindrical cut of a MgF2 single crystal, intricate interference patterns have been observed during recent experiments at the Institut Laue Langevin. If new SRFs exist and interact with the neutrons in the whispering gallery through the nuclei in the crystal, these interference patterns will be perturbed. To look for those perturbations in the latest measurements, and to constrain SRF models, a theoretical model was developed to describe the observed interference patterns as a superposition of quasi-stationary states in a finite potential well. The potential well is formed by the optical potential of the crystal and the centrifugal force experienced while propagating along the surface of the cylinder. To incorporate the effects of the roughness of the mirror and the SRFs on the quasi-stationary states and their energies, logarithmic perturbation theory was used. A description of this model will be presented as well as the first analysis of the most recent experimental campaign.

Speaker: Jason Pioquinto (University of Virginia; Institut Max von Laue Paul Langevin)

PioquintoISINN-31.pdf

10 The Neutrino Electron Correlation Coefficient in Neutron Beta Decay

One of the current problems of the Standard Model of Elementary Particle Physics is the about three sigma failure of the first-row unitarity test of the Cabbibo-Kobayashi-Maskawa matrix. A long-standing goal of the study of free neutron beta decay is a better determination of its upper left element ("Vud"). That is possible with measurements of the neutron lifetime and a correlation coefficient: the beta asymmetry "A" or the neutrino electron correlation coefficient "a". In this talk, I will present a recent measurement of the neutrino electron correlation coefficient with aSPECT, and I will present commissioning data from a next generation experiment, Nab. The Nab collaboration is working on an improvement in the accuracy of neutrino electron correlation coefficient that - if achieved - is substantial enough to base the determination of Vud on neutron beta decay data alone.

Speaker: Stefan Baessler (University of Virginia)

ISINN_2025_baessler.pdf

15:40 Coffee Break

Plenary Session

Convener: Zhigang Ge

11 Introduction to Neutron Activation Analysis at the IBR-2 Reactor, FLNP JINR

Neutron activation analysis due to its high accuracy, reproducibility and nondestructive nature is a technique widely used in the environmental, material, archeological, geological and nanotoxicological studies. Favorable features of neutron activation analysis will be highlighted in the presentation and the principal of its realization on the installation REGATA of the IBR-2 reactor will be presented. Examples of application of neutron activation analysis as well as complimentary technique for the assessment of heavy metal deposition using active and passive moss biomonitoring, water biomonitoring and development of the approaches for wastewater treatment, medicinal plants analysis will be given. Besides, the effects of metal nanoparticles on different living organisms will be discussed. The information is addressed to researchers interested in the applications of neutron activation analysis or to those who are searching for an analytical technique suitable for environmental, biomedical, geological, etc. studies.

Speaker: Inga Zinicovscaia (JINR)

Zinicovscaia_NAA_ISINN_31.pptx

12 Neutronic Characteristics of Metal Hydride Moderators and Their Applications in Microreactors

Neutronic Characteristics of Metal Hydride Moderators and Their Applications in Microreactors

Speaker: Lipeng Wang (NINT)

13 Energetic Dependence of Neutron-Induced Single Event Upsets, and Its Impact on Atmospheric Neutron SER Prediction

Energetic dependence of neutron-induced single event upsets, and its impact on atmospheric neutron SER prediction

Speaker: Chao Qi (NINT)

Academic Journal Promotion Session

Convener: Zhigang Ge

14 (Withdrawn) Nuclear Science and Techniques

Speaker: Lihua Sun (孙丽华)

15 Chinese Physics C

Speaker: Hairong Dong (董海荣) (IHEP, CAS)

CPC-ISINN.pdf

16 Radiation Detection Technology and Methods

Speaker: Yanjin Wang (王岩瑾) (IHEP, CAS)

RDTM-Yanjin Wang0526.pdf

17 Natural Science Review

Speaker: Alexander Nezvanov (JINR)

18:00 Dinner

Tuesday, 27 May

Parallel Session 1: Fundamental interactions & symmetries in neutron induced reactions/Properties of compound states, nuclear structure/Intermediate and fast neutron induced reactions/Nuclear fission: (1)

Convener: Maxim Karetnikov (FSUE All-Russian Scientific Research Institute of Automation)

18 A New Scheme of Space-Based Measurement of Neutron Lifetime

How long neutrons survive plays a key role in particle physics and cosmology. However, conflicting results with a deviation of about 9 second have been found over years in neutron lifetime measurements. Different ideas have been proposed to solve such deviations. We proposed a new scheme based on CubeSat to determine neutron lifetime. In this talk, after a short overview on the lifetime puzzle, I will show the principle of our proposed measurement, the challenges and also the progress in payload development.

Speaker: Xiaopeng Zhou

20250526-ISINN31-zxp(2).pptx

19 The Precise Measurement of Triton-Producing Three-Body Breakup Reaction of 7Li Nucleus Induced by Fast Neutrons with the Multi-purpose Time Projection Chamber at CSNS

Tritium is important in fusion facility and one of the main ways to realize tritium production is the triton-producing reaction of lithium nucleus induced by neutrons. Generally the cross section of neutron induced triton-producing reaction of 6Li has a large value in a wide range of neutron energy, while in the energy range of fast neutron the triton production is dominant by the reaction of 7Li nucleus. In the research of Molten Salt Reactor (MSR) the cross section data of triton-producing reaction of 7Li will significantly influence the estimation of tritium production and the design of reactor. The cross section data of triton-producing reaction induced by fast neutrons is important for the calculation of tritium yield and tritium breeding rate In the research of fusion facility. The triton-producing reaction of 7Li is a three-body reaction, including the sequential decay, the quasi-elastic scattering and the direct breakup processes. The double differential cross section data and integral craoss section data are necessary for the theoretical model construction and fitting parameters constraint. Currently the data of 7Li triton-producing reaction are mainly the integral cross section data and double differential data of secondary neutrons, and the double differential data of secondary charged particles are scarce, limiting the further research of reaction theory. The precise measurement of triton-producing reaction of 7Li is limited by the technology of detection and measurement. Considering the latest developed Multi-purpose Time Projection Chamber (MTPC) at CSNS, it is possible to measure the kinetic process of triton-producing reaction of 7Li by the momentum and energy reconstruction of the secondary particles. And the systematic measurement of the reaction will be conducted at the Back-n white neutron source to provide more data sets in details for theoretical model construction and data evaluation.

Speaker: Han Yi (CSNS)

yih-MTPC_7Li(n,nt)a_ISINN31-v2.pdf

20 Geant4 Simulation of the Energy Resolution Function for the CSNS Back-n Facility

The Back-n facility at the China Spallation Neutron Source (CSNS) is a newly-built neutron time-of-flight facility providing white neutrons. It is characterized by the high neutron flux, wide energy range, and good energy resolution. As one of the essential parameters, the Energy resolution function (ERF) has a significant impact on nuclear data measurements and related neutron techniques, such as the neutron resonance analysis. The ERF represents the inherent broadening effects in the determination of neutron energy that are due to the spallation target assembly system. These effects can be studied using the Geant4 Monte-Carlo toolkit, benefiting from its flexible capabilities of particle tracking and information recording. In this simulation work, the model of the Target Moderator-Reflector (TMR) system was constructed. The TMR system primarily consists of 11 tungsten targets encapsulated in tantalum shells, reflector models, and different types of moderators, such as the decoupled water moderator (DWM), decoupled poisoned hydrogen moderator (DPHM), and coupled hydrogen moderator (CHM). The “equivalent moderate distance” (λ), defined as the product of the moderation duration of the neutrons inside the target assembly and their velocity at the target emitting surface, was obtained. The RPI (Researchers at Rensselaer polytechnic Institute, RPI) function was fitted using the parameter λ to derive the ERF, and it demonstrates effective performance within the 1-100 eV range.

Speaker: Shengda Tang (SYSU)

21 Test of the T-Invariance with Polarization-Asymmetry Theorem in Mirror Reflection of the Slow Neutrons

A possibility of the test of T - invariance violation in neutron - nuclear interaction in the multiple mirror reflections of slow neutrons is considered. The reflections are assumed in a "whispering gallery" mode. It is shown that an expected effect may exceeds in magnitude a correspondent effect near p - wave resonance. The methodical features of such experiment are considered.

Speaker: Vadim Skoy (Joint Institute for Nuclear Reserch)

22 Faddeev-AGS Calculation of Neutron Induced Nuclear Reaction on Deuteron within Wave-Packet Continuum Discretization Approach

The n+d reaction is one of the most fundamental three-body nuclear reactions, which is an important platform for examining the nucleon-nucleon interaction. The wave-packet continuum discretization approach is developed to solving three-nucleon scattering equations within a modified Faddeev-AGS equation framework, which is based on the discretization representation of the three-body continuum states and lattice representation of all scattering operators in momentum space. As an application, calculations were performed for n+d reactions with realistic nucleon-nucleon interactions. The calculated results, including the elastic scattering angular distributions, triple differential breakup cross section, double differential cross sections of the emitting neutrons and protons and so on, were in fair agreements with the experimental data as well as the evaluated data in CENDL-3.2, ENDF/B-VIII.0, JENDL-5 and JEFF-3.3.

Speaker: Wendi Chen (Beihang University)

ISINN-chen.pdf

Parallel Session 2: Nuclear data for applied and scientific purposes/Neutron detection & Methodical aspects: (1)

Convener: Changlin Lan (Lanzhou University)

23 Measurement of the Differential Cross Sections of 6Li(n, t)4He Reaction at CSNS Back-n White Neutron Facility

The cross section of 6Li(n, t)4He reaction is adopted as standards up to 1 MeV due to its relatively high cross-section. However, in the neutron energy above 0.5 MeV, it was indicated that the cross section might be overestimated by evaluated data, such as ENDF/B-VIII.0 and JEFF-3.3 [1]. Besides, due to the high Q value (4.78 MeV), the 6Li(n, t)4He reaction is widely used in neutron detection in various nuclear physics experiment and other applications, for example, tritium production for fusion reactors. However, in few MeV energy region, the experimental data on the 6Li(n, t)4He reaction are quite limited, and discrepancies among different measurements and evaluations were found for an energy range above 3.0 MeV [2]. In addition, the differential cross section of 6Li(n, t)4He reaction could provide information on the excitation levels of the compound nucleus 7Li.

In order to resolve the discrepancies and to improve the accuracy of 6Li(n, t) 4He differential cross section in the 3-6 MeV neutron energy region, the 6Li(n, t)4He reaction was measured at the China Spallation Neutron Source (CSNS) Back-n white neutron source. The differential cross-sections of the 6Li(n, t)4He reaction at 7 detection angles ranging from 21.4° to 90° are obtained with Si-PIN detectors for neutron energy from 40 keV to 6.8 MeV. The measured cross section will be presented in the talk, the comparison between the present differential cross-sections with existing data and evaluations, as well as R-matrix calculations will be shown.

Speaker: Wei Jiang (CSNS)

24 (Withdrawn) Non-Statistical Effects in (p, γ) Reactions and in β-Decays

The characteristics of various nuclear processes are rather simple to calculate in statistical model [1,2]. In particular, the transition-width distribution is described by the Porter–Thomas equation, there are no correlations between different partial widths, the strength function of $\beta$-transitions $S_\beta (E)$ depends smoothly on energy, and the ratios of the amplitudes for decay via various spin channels follow the Cauchy distribution.
Deviations from the statistical theory have been observed in (p,p’γ ) and (p,γ ) reactions, $\beta^-$ and $\beta^+/EC$-decays [1-4]. Non-statistical effects are closely related to the symmetry of the nuclear interaction and intermediate resonance structure [3,4].
In this report non-statistical effects manifested in reactions involving low-energy protons and in β- decay are analyzed. In (p,γ) reactions for non-analog resonances in N>Z nuclei non-statistical effects are connected with neutron excess and domination of the simple configuration such as proton-particle neutron-hole in the wave function of nonanalog resonances [1-3]. The association of non-statistical effects in (p,γ) reactions and in the $\beta$-decays with spin–isospin $SU(4)$ symmetry are discussed. The non-statistical effects taking into account non-statistical correlations in $E2$ and $M1$ γ-transitions for the γ-decay of the non-analog resonances in (p,γ) reactions are analysed.

[1] I.N. Izosimov, Physics of Particles and Nuclei, 30,131(1999).
[2] I.N. Izosimov, JINR Preprint E6-2024-14. Dubna, 2024; http:www1.jinr.ru/Preprints/2024/14(E6-2024-14).pdf.
[3] I.N. Izosimov, et al, Phys. Part. Nucl., 42,1804(2011). DOI:10.1134/S1063779611060049
[4] O.E. Kraft, Yu.V.Naumov, V.M.Sigalov, I.V. Sizov, Sov. J. Part. Nucl., 17, 573 (1986).

Speaker: Igor Izosimov (JINR)

25 Measurement of CSNS Back-n Neutron Beam Profile with Micromegas

The Back-n white neutron beam line, which uses back-streaming white neutrons from the spallation target of the China Spallation Neutron Source, is used for nuclear data measurements. A Micromegas-based neutron detector with two variants was specially developed to measure the beam spot distribution for this beam line. In this article, the design, fabrication, and characterization of the detector are described. The results of the detector performance tests are presented, which include the relative electron transparency, the gain and the gain uniformity, and the neutron beam profile reconstruction capability. The result of the first measurement of the Back-n neutron beam spot distribution is also presented.

Speaker: Yang Li (CSNS)

3+Yang_Li@ISINN-31.pptx

26 (Withdrawn) New Measurement of 165Ho Neutron Capture Cross Section Data

The neutron capture cross section data for $^{165}$Ho were measured at the Back-streaming White neutron beam line (Back-n) of China Spallation Neutron Source (CSNS) using total energy detection systems, which is comprise a set four C$_6$D$_6$ scintillator detectors coupled with pulse height weighting techniques.
The resonance parameters were extracted using the multilevel, multichannel R-matrix code SAMMY, fitting the measured capture yields of the $^{165}$Ho(n,$\gamma$) reaction in the neutron energy range below 100 eV. Subsequently, the resonance region capture cross sections were reconstructed based on the obtained parameters. Additionally, the unresolved resonance average cross section of $^{165}$Ho(n,$\gamma$) reaction was determined relative to the standard $^{197}$Au sample within the neutron energy range of 2 keV to 1 MeV. The experimental data were compared with the recommended nuclear data from the ENDF/B-VIII.0 library, as well as TALYS-1.9 code calculations. The comparison indicates that the measured $^{165}$Ho(n,$\gamma$) cross sections are in good agreements with these data. The present results are significant for evaluating the $^{165}$Ho neutron capture cross section data, enhancing the quality of evaluated nuclear data libraries, and providing valuable guidance for nuclear theoretical models and nuclear astrophysical studies.

Speaker: Suyalatu Zhang (IMUN)

27 A Latest Result of the Neutron Capture Yield of 197Au Measured by the C6D6 Experimental Set-up System in Back-n

Since the foundation of Back-n beam line in CSNS, the capture cross section of $^{197}Au(n,\gamma)$ had been measured twice. Considering the lower energy zone and high level of background of previous results, however, we aim to process the yield result to 1 MeV, and analyze the resonance parameters: resonance peak, Gamma width and incident neutron width from 1 eV to 2 keV that belongs to the Resolved Resonance Range(RRR), using M6-version SAMMY code.

Speaker: Zhanqiao Cui (SUSTech)

10:25 Coffee Break

Parallel Session 1: Fundamental interactions & symmetries in neutron induced reactions/Properties of compound states, nuclear structure/Intermediate and fast neutron induced reactions/Nuclear fission: (2)

Convener: Baohua Sun (Beihang University)

28 Measuring B_nat(n, tot) Reaction as an International Standard

The final accuracy of the evaluations relies on the quality of the experimental datasets
being used. But, conversely, the quality of the experimental datasets relies on the quality of the
standards used as reference. Big improvements have been done in the last decade, after the
IAEA launched an international project for the “Maintenance of the Neutron Cross-Sections
Standards”, adopting the upgraded version of the GMAP code from ENDF/B. Present Nuclear
Data Standards (IAEA NDS) are those collected by A.D. Carlson et al in [1], where it is
explained how the short table of principal international standards –the so-called Thermal
Neutron Constants (TNC) together with the specific neutron cross-sections of light elements
(H, Li6 and B10)- play a relevant role in the whole NDS evaluation by adopting the upgraded
version of the GMAP code from ENDF/B.
Mention must be made of the fact that these TNC –which include (n,f), (n,g) and (n,el)
reactions– cannot be directly measured as “absolute”, trailing so an USU (Unknown Systematic
Uncertainty) [see 2] that cannot be removed by statistical analysis. New inputs are needed to
increase the quality of this international effort and one of the most sensitive points is the
standard value at thermal point of the B10(n,α) reaction, which experimental uncertainty
depends on the acknowledge of the flux of the used neutron source.The interest in measuring
the B_nat(n,tot) reaction as a way to improve the B10(n,α) standard is discussed in this work.
Looking for an absolute Standard around thermal an near-epithermal energy region, the
B_nat(n,tot) cross section is well suited because it can be accurately obtained from a neutron
transmission experiment by using cumulative thin samples, and based on integrating the cross
section function over a wide energy interval. The method and a possible experimental setup
will be presented in this work.
REFERENCES
[1] A. D. Carlson, V.G. Pronyaev, R. Capote et al., “Evaluation of Neutron Data Standards,”
Nucl. Data Sheets 148, (2018)142–187.
[2] R. Capote, S. Badikov, A.D. Carlson et al., “Unrecognized Sources of Uncertainties (USU)
in Experimental Nuclear Data,”
Nucl. Data Sheets 163, (2020)191–227.

Speaker: Ignacio Durán (Universidad de Santiago de Compostela)

29 Application of Tagged Neutron Technology for Applied and Fundamental Nuclear Problems

A nanosecond tagged neutron technology (NTNT) is based on the space-time analysis of events produced by the 14 MeV neutrons which time of escape, energy, and direction of movement is known by the recording of the accompanying alpha-particle. The development by FSUE VNIIA of the high-intensity generator of tagged neutrons promoted the extension of the applications of tagged neutrons. Currently, the NTNT is used for the neutron activation analysis as well as for applied and fundamental nuclear problems due to the following advancements:
• Measuring the neutron flux with the absolute inaccuracy less than 5% and relative inaccuracy less than 1% in the high range of neutron generator intensity.
• Directional reading of the angle of the tagged neutron escape with the accuracy up to 0.02 rad, and measuring the coordinates of nuclear reactions stipulated by tagged neutrons.
• High effect/background ratio provided by the space-time discrimination of events stipulated by interaction of “untagged” neutrons and secondary radiation with the matter.
• Possibility of gamma-detector calibration while measurement by special object-calibrators when tagged neutrons are passing through them, the emitted gamma-lines can be easily interpreted on the NTNT spectrum (alpha-gamma coincidences);
• Possibility of gamma-detector calibration while measurement by reference isotope sources, the gamma-lines can be defined by the gamma-spectrum without coincidences and they practically do not affect the NTNT spectrum.
The several applications of NTNT are considered in the report:
• Precise 14 MeV neutron flux generation for nuclear detector calibration;
• Determination of gamma-detectors response to 14 MeV neutrons;
• Measuring the angle distribution and Doppler effect of gamma-rays emitted at the inelastic neutron scattering.
The experimental technique and results are considered. The obtained data are in a good agreement with the numerical calculations and experimental data by other authors.

Speaker: Maxim Karetnikov (FSUE All-Russian Scientific Research Institute of Automation)

30 Research on Neutron Flux Measurement of CSNS Back-n

The Back-streaming neutron beamline (Back-n) at the China Spallation Neutron Source (CSNS) is a newly built time-of-flight facility that provides white neutrons. The neutron flux of Back-n is of crucial importance for the feasibility studies and data analysis of experiments conducted utilizing this resource. In particular, the accurate flux is a prerequisite for conducting high-precision nuclear data measurement. The energy region of Back-n is exceptionally broad, spanning 10 orders of magnitude, and includes two endstations (ES#1 and ES#2) with various beamline configurations to accommodate different beam requirements. Consequently, systematic and comprehensive research is essential.
The flux from 0.3 eV to 150 keV was measured using a Li-Si monitor, while the flux from 150 keV to 300 MeV was measured using a fission ionization chamber. Experiments revealed and confirmed spectral differences between ES#1 and ES#2, with discrepancies reaching up to 20% in the 0.3 eV to 150 keV range, thereby clarifying longstanding inconsistencies in neutron capture cross-section measurements. Additionally, it was observed that the shape of the energy spectrum remained unchanged despite the increase in CSNS accelerator power from 20 kW to 125 kW between 2018 and 2022. However, with the power expected to reach 170 kW in 2024, adjustments in the beam window structure have led to changes in the energy spectrum shape. Furthermore, it was found that the shape of the energy spectrum varies with the beam profile; the large beam spot (60-60-60) in ES#2, exhibits a consistent spectrum shape with the combined beam spot (60-30-30), yet it significantly differs from the small beam spot (30-30-30).

Speaker: Yijia Qiu (CSNS)

31 Primary Gamma Transitions in 176Lu and 177Lu after Resonance Neutron Capture

$^{\text{175, 176}}\text{Lu}$ (n,γ) $^{\text{176, 177}}\text{Lu}$ reactions were studied via radiative capture of resonance neutrons at the CSNS Back-n White Neutron Source. Using the time-of-flight (ToF) technique, gamma-ray spectra for isolated resonances were measured. The experiment was conducted with a coaxial HPGe gamma detector equipped with an anti-Compton system, positioned 20 cm from the target. A 60 g sample of metallic natural lutetium ($^{\text{nat}}\text{Lu}$) with 99.9% purity (dimensions: 60 × 2.2 mm) was used as the target, located 76 m from the spallation target in the ES#2 experimental hall. The ToF spectrum was measured in the 1–700 eV energy range, with sufficient γ-ray statistics up to 100 eV. The measurement time was approximately 200 hours. The ToF resolution enabled the extraction of gamma-ray spectra from 16 neutron resonances for the $^{\text{175}}\text{Lu}$ (n,γ) $^{\text{176}}\text{Lu}$ reaction. Due to the low natural abundance of $^{\text{176}}\text{Lu}$ (2.6 %), gamma-ray spectra were obtained from 10 resonances for $^{\text{176}}\text{Lu}$ (n,γ) $^{\text{177}}\text{Lu}$ reaction. In total, 40 primary gamma transitions were identified for $^{\text{176}}\text{Lu}$, but 15 for $^{\text{177}}\text{Lu}$. Resonance spins were also deduced from the analysis of gamma-transition intensities for both reactions.

Acknowledgment
We thank the staff members of the Back-n white neutron facility (https://cstr.cn/31113.02.CSNS.Back-n) at the China Spallation Neutron Source (CSNS) (https://cstr.cn/31113.02.CSNS ), for providing technical support and assistance in data collection and analysis.

Speaker: Gadir Ahmadov (JINR)

32 Investigation of Properties of Low-Level p-Wave Neutron Resonances at the IREN Facility (FLNP, JINR, Dubna)

Speaker: Natalia Rebrova (FLNP JINR)

33 Measurements of the Gamma-Ray Emission Cross Sections and Angular Distributions from (n, xγ) Reactions with 14.1 MeV Neutrons

The study of inelastic scattering of fast neutrons by atomic nuclei is of great importance for both fundamental and applied neutron-nuclear physics. Reactions induced by neutrons provide a unique source of information for describing the processes of strong interaction between nucleons.
Inelastic scattering processes are utilized to study the characteristics of excited states of target nuclei [1]. The practical application of the (n,n'γ) reaction necessitates the expansion and refinement of experimental data on this process. Research on the inelastic scattering of fast neutrons has recently become more active, driven by new prospects for nuclear energy production using fast neutron reactors.
The purpose of this experiment was to refine the available data on emission cross sections and angular distributions from the inelastic scattering of 14.1 MeV neutrons by certain light nuclei. This work was conducted within the framework of the international TANGRA (TAgged Neutrons and Gamma RAys) project at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research in Dubna, Russia.
Inelastic scattering was studied using the Tagged Neutron Method [2], in which neutrons with an energy of 14.1 MeV, produced in the d(t,a)n reaction, are “tagged” by detecting alpha particles. Gamma quanta from the (n,n'γ) reaction were recorded using a new multidetector system [3]. The experimental data are presented and discussed in comparison with previously published results.

Acknowledgment
This work was conducted with financial support from the Russian Science Foundation (grant no. 23-12-00239).

1. W. Hauser and H. Feshbach. The Inelastic Scattering of Neutrons, Phys. Rev., 1952, vol. 87,
   p. 366., https://doi.org/10.1103/PhysRev.87.366.
2. I.N. Ruskov, Yu.N. Kopatch, V.M. Bystritsky et al. Physics Procedia, vol. 64, 2015, pp. 163-170,
   ISSN 1875-3892, https://doi.org/10.1016/j.phpro.2015.04.022.
3. Yu.N. Kopatch, D.N. Grozdanov, N.A. Fedorov et al. Moscow University Physics Bulletin, vol. 79,
   No 3, pp. 308-317, 2024. https://istina.msu.ru/publications/article/683109723/.

Speaker: Dimitar Grozdanov (JINR)

Parallel Session 2: Nuclear data for applied and scientific purposes/Neutron detection & Methodical aspects: (2)

Convener: Wei Jiang (高能所)

34 Direct Neutron Fluence Measurement with a Novel Spherical Long Counter

Efficient and practical neutron detectors are crucial in many areas, including national security, medicine, crystallography, and astronomy. As commonly used neutron detectors, 3He-gas-filled proportional counters still play an irreplaceable role in neutron fluence monitoring. 3He tubes are used directly to detect the thermal neutron, but the measurable neutron energy range is often extended by adding moderating materials, so-called long neutron counters. Long cylindrical counters have attracted much attention due to their easy range extension. Nevertheless, the large fluctuation of the energy response due to the neutron incidence direction has not been solved, which directly limits the application of long counters in neutron flux detection. Therefore, it is necessary to conduct innovative research on neutron detectors to measure neutron fluence more accurately and conveniently. We previously reported the physical design of a new spherical long counter for the first time. The spherical long counter has a stable neutron fluence energy response in the energy range from 0.01eV to 20MeV, and the angular response difference in 4π space is no more than 16.5%. Here we show the further development of the spherical long counter and the results of its verification using different types of neutron sources., including D-D, D-T quasi-monoenergetic accelerator neutron source, Am-Be, 252Cf isotopic neutron source, reactor thermal neutron source, and spallation neutron source. The angular and fluence responses of the spherical counter are examined, and the maximum angular response difference is 5.86%. The new detector we developed can adapt to the accurate measurement of multi-energy and multi-occasional neutron sources for direct neutron flux measurement.

Speaker: Changlin Lan (Lanzhou University)

35 Model of Experiments and a Method of Analysis of Data for Determination of Absorbed Dose of Samples for Applied Research at the NICA Facility

Model of experiments for applied research at the Nica facility are developed and manufactured. Model includes two ionization chambers IK-1, IK-2, strip and phosphor chambers for measure profile with coordinate and intensity of beam and various sample holders with different geometry. At those chambers, the materials of electrodes are used different, at the IK-1 it is foil-clad fiberglass, for the IK-2 are taken foil-clad polyimide One of the ionization chambers will be assembled before irradiated samples, other mounted after. The strip chamber will be added for measure the coordinate of beam or it will replace the IK-2 ionization chambers. By the phosphor chambers will be tracked and follow the profile of beam. The chambers IK-1 and IK-2 have been tested on a 60Co gamma source and a 150 MeV proton beam at the accelerator “Prometheus” at the Tsyba MRRC (Obninsk).
A method for analysis of the intensity and profile data by using the 3.8 GeV/nucleon 124Xe54+ ion beam data is developed. The method is necessary to provide the precise determination of the fluence and absorbed dose for irradiated materials. The beam profile and intensity distributions together with overall intensity and duration of radiation exposure are used for the developing the method of analyzed for the set of samples of different geometry and chemical composition. The analyzed raw data were taken in the long-term exposure mode. Software was developed for investigation of intensity and profile of the beam. Because the data is a sequence of intensity values per short run, each run will be analyzed separately. The intensity will be measured before collision with the target for what were require additional study on how the intensity decreases after passing through each detector and approximation of the intensity, which reaches a particular sample. Distributions of beam intensity and profile versus exact duration of irradiation will be obtained for each investigated sample. Each sample will be at the beam sequentially in series that results in individual profile for particular sample. The distributions will be obtained by the developed software for the input data and further precise calculation of energy losses and absorbed dose in irradiated materials. Those several different parameters necessary to investigate and explore, the uncertainty is under study.
The study is performed within the ARIADNA Collaboration.

Speaker: Nelli Pukhaeva (JINR)

36 Estimation of Cosmic Muon-Induced Neutron Yields via Muon Spallation in Deep Underground Environments Using (e, e‘xn) Cross-Section Measurements of 181Ta

Cosmic muon-induced fast neutrons are one of the main sources of neutron background in deep underground environments. Due to the high energy and low flux of cosmic muons, it is challenging to directly measure the neutron yield. According to the Weizsäcker-Williams virtual photon method, when the energy transfer is less than one-tenth of the kinetic energy of the lepton, the Coulomb excitation process of leptons with the same relativistic factor is analogous. Therefore, by measuring the neutron yield produced by electron Coulomb excitation, we can estimate the cosmic muon-induced neutron yields via muon spallation in detectors and provide an estimate of the lower bound of neutron background in deep underground measurements. In this study, the cross sections of the 181Ta(e, e′xn; x = 1–8)181−xTa reactions induced by electrons with energies ranging from 20 to 110 MeV were measured. Discrepancies between the experimental data and the TALYS code predictions were observed, which were attributed to the nuclear level density model in TALYS not accurately describing the Ta nuclei. Consequently, the model selection and its parameterization were optimized. Based on the measurement results, the neutron yield produced by cosmic muons in detectors—serving as a lower limit for the neutron background in deep underground measurements—was estimated per unit mass of detector material per unit time.

Speaker: Yuqi Yang (Tsinghua University)

ISINN31-Yuqi Yang.pdf

37 Measurement of the 6Li(n, t)4He Cross Section with Multi-purpose Time Projection Chamber at the Back-n White Neutron Source of CSNS

Neutron-induced reaction 6Li(n,t)4He plays an important role in nuclear energy and nuclear data evaluation. The cross section of 6Li(n,t)4He has been adopted as standard in the energy range of 0.0253eV–1.0MeV [1], and is commonly used as reference for other cross section measurements. Previous works have shown non-negligible discrepancies in cross section results [2,3,4], and the angular distribution data in high neutron energy region are scarce.
The multi-purpose time projection chamber (MTPC), which is designed for measuring neutron nuclear data of varied field, has been fabricated in the back-streaming neutron facility (Back-n) at China Spallation Neutron Source (CSNS). The detector is able to measure the charged particles emission from neutron-induced reactions. We have carried out an experiment with MTPC for measuring the total cross section as a function of neutron energy and the differential cross section as a function of the product particle emission angle of 6Li(n,t)4He in the energy range of 0.5eV–100keV. In the experiment, we use a Lithium Fluoride sample with the aluminum substrate as the target, and a gas composition of 93% Argon and 7% Carbon Dioxide is used. Different experimental conditions were set for measuring different emission particles.
In this work, detector design and experiment setup are firstly introduced. Then the data analysis of MTPC is discussed in detailed, and results of total cross section and differential cross section is presented. Finally, an upgrade on the detector is shown as a new measurement of the 6Li(n,t)4He in the energy range of 100keV-10MeV is on schedule.
Reference:
[1] A. D. Carlson et al. Nuclear Data Sheets, 148:143–188, 2018.
[2] M. Devlin et al. AIP Conference Proceedings, 1090(1):215–219, 2009.
[3] Leo E. Kirsch and other. Nucl. Instrum. Meth. A, 874:57–65, 2017.
[4] P. S. Prusachenko and T. L. Bobrovskiy. Eur. Phys. J. A, 60(1):12, 2024.

Speaker: Hongkun Chen (Sun Yat-sen University)

38 Analysis of Chlorine Neutron Capture Experiment for Efficiency Calculation Validation

The TANGRA project is aimed at studying the inelastic scattering of 14.1 MeV neutrons from the ING-27 neutron generator on various atomic nuclei using the tagged neutron method. To register gamma rays from the interaction of neutrons with nuclei, we use HPGe and LaBr3(Ce) detectors. To perform high-precision measurements, the energy calibration and counting efficiency of the detectors were determined using standard point gamma sources and prompt gamma rays from neutron capture on chlorine nuclei. In addition to the experimental data, the dependences of the gamma-quanta registration efficiency on energy for two types of detectors were obtained using Monte Carlo (MC) simulations in GEANT4. In this work we will present the results of efficiency measurements and compare them with calculated data.

Speaker: Constantin Hramco (JINR)

ISINN-31_Hramco_C.pdf

ISINN-31_Hramco_C.pptx

39 Measurement of Relative Differential Cross Sections of the 1H(n, n)1H Reaction in the Neutron Energy Range from 0.45 MeV to 8.5 MeV

The 1H(n, n)1H reaction is important for fundamental physics research, neutron cross-section standards, and nuclear data evaluation. However, there are few differential cross-section data for this reaction in several MeV neutron energy regions. The relative differential cross sections of the 1H(n, n)1H reaction was measured at the Back-n white neutron source of the China Spallation Neutron Source (CSNS). A 500 nm thick Mylar film was used as the sample for experimental measurements. The charged particles produced by the 1H(n, n)1H reaction were detected using the ∆E−E telescope array and Silicon detector array of the Light-charged Particle Detector Array (LPDA) spectrometer. The relative differential cross sections of the 1H(n, n)1H reaction in the center-of-mass system from 66° to 142° in the neutron energy range from 0.45 MeV to 8.5 MeV were obtained from 8 Silicon detectors in the ∆E−E telescope array and the Silicon detector array. This work is an extension of the previous measurement in the neutron energy range from 6 MeV to 52 MeV. The present results are in good agreement with the previous measurement results and evaluation data.
Keywords: 1H(n, n)1H reaction, differential cross sections, Back-n white neutron source, LPDA

Speaker: Kang Sun (CSNS)

Measurement of relative differential cross sections of the n-p scattering reaction in the neutron energy range from 0.45 MeV to 8.5 MeV.pptx

12:25 Lunch

Parallel Session 1: Fundamental interactions & symmetries in neutron induced reactions/Properties of compound states, nuclear structure/Intermediate and fast neutron induced reactions/Nuclear fission: (3)

Convener: Jie Ren (China Institute of Atomic Energy)

40 Progress in the Measurement of the Neutron-Induced Fission Cross-Section at CSNS Back-n

China Spallation Neutron Source (CSNS) is a newly built large scale facility in 2018. It is generating neutrons by bombarding 1.6 GeV protons into a tungsten target for multidisciplinary research. A back-streaming neutron beamline (Back-n) at CSNS is built at the reverse direction regarding to the proton beam mainly for the nuclear data measurement. Back-n is characterized by its wide energy range (from thermal to 300 MeV), high flux (up to 10$^7$ n/cm$^2$/s at 77 m) and good energy resolution (less than ~1% below 1 MeV), which stands as one of the state-of-the-art white neutron source in worldwide. Fission cross-section of a series of isotopes, such as $^{232}$Th, $^{235}$U, $^{236}$U, $^{238}$U, $^{239}$Pu, has been measured in wide energy ranges since 2018, and more isotopes (such as minor actinides) are planned to be measured in the near future. In this presentation, the CSNS Back-n facility and the campaigned fission cross-section measurement will be reviewed. Then the challenges and perspectives of the fission cross-section measurement at CSNS Back-n will be highlighted.

Speaker: Yonghao Chen (CSNS)

Yonghao_Chen_ISINN31.pptx

41 Prompt Fission Neutron Spectra and Angular Distributions Measured in Narrow Windows of Fragment Masses and Total Kinetic Energies: A Puzzling Result and a Possible Explanation

A previous experiment performed at JRC-Geel on prompt fission neutrons (PFN) in correlation with fragments from spontaneous fission of 252Cf was repeated using an improved setup and much better statistics. The experiment lasted 3 months and 68×106 coincident events were collected. In this new experiment PFN spectra and angular distributions (in the laboratory system) are selected in a narrow window of fragment masses and total kinetic energies around AL=109 and TKE=184 MeV, AL=120 and TKE=193.5 MeV, AL=109 and TKE=184 MeV. In this way we have isolated (as good as possible) certain fission paths which makes comparisons with theoretical models easier.

Clear deviations from a Maxwellian spectrum were found from 0.5 to 6 MeV. They consist in
structures, more pronounced around the most probable energy (≈1 MeV). There is a resemblance with the deviations predicted by the dynamical scission model, which assumes that PFN are emitted during the separation of fragments at scission. Concerning the angular distribution, deviations from a smooth curve are observed in the form of fine structures. They could be the sign of scattering of neutrons on the just born fragments.

Finally, oscillations are shown to be present also in the inclusive angular distribution since the
sample of events over which the summation is done is not large enough to completely wash out the structures.

At first look, these identified structures in the data are not compatible with the traditional hypothesis that PFN are evaporated from fully accelerated fragments, because this hypothesis predicts smooth distributions

Speaker: Nicolae Carjan (FLNP, JINR)

42 A New Method for Determining the Transverse Vibration Energy of Fission Prefragments

The study of the dynamics of heavy nuclei fission remains a relevant problem in modern nuclear physics. One of the key questions in this field is the identification of the mechanism of spin formation of the fission fragments, which is still insufficiently studied. In this work, based on studies [1,2], a modelling of the potential energy of the compound fissile system has been performed to analyse the role of transverse oscillations in the spontaneous fission process of the $\rm ^{252}Cf$ nucleus. The focus of the study was directed towards wriggling and bending oscillations, which may play a role in the final spin distribution of the fission fragments.

The calculation method is based on the use of an effective nucleon-nucleon potential [3] to estimate the potential energy of the transverse oscillations. Furthermore, the concept of a "cold" nucleus [4] has been used, which implies that all excitation energy is converted into non-equilibrium deformation energy during the entire fission process, simplifying the analysis of collective oscillations and their influence on the spin distribution. The proposed model includes a number of parameters, including charge and mass asymmetry, distance between fragments, and quadrupole deformations. The frequencies of the oscillations and the stiffness coefficients are calculated numerically, allowing the contribution of each type of oscillation to the final distribution [5,6] of the spins of the fission fragments to be determined. The validity of the model has been verified with experimental data [7] on spin distributions.

The analysis of the results obtained confirms that mentioned types of oscillations make a significant contribution to the process of fission fragments spins formation. Nevertheless, the ratio between the energies of wriggling and bending oscillations remains approximately constant, which is consistent with theoretical predictions for symmetric fission path described in [8]. The findings of this study indicate that the outcomes obtained within the framework of the hydrodynamic approach [9] are more closely aligned with the observed spin values. This confirms the importance of considering collective effects in describing the fission mechanism of heavy nuclei.

In addition, the influence of the initial deformation conditions of the nucleus on the nature of the transverse vibrations and the final distribution of the spins of the fragments has been considered. The inclusion of non-equilibrium deformations allows a more accurate prediction of fission parameters, especially near the scission point. Important correlations between transverse oscillations and angular momentum redistribution processes have been identified, confirming their key role in the formation of fission fragments. Further analysis can be directed towards studying the influence of temperature effects and interactions between fragments in the final stages of fission.

This study contributes to the refinement of the mechanisms of energy and angular momentum transfer in the process of nuclear fission. The results obtained can be used to improve theoretical models and to predict the characteristics of the fission products of other actinide nuclei. In the future, it is planned to extend the research to other heavy nuclei and to use more detailed quantum mechanical models to describe the dynamics of the collective oscillations in the fission process.

References

1. G. G. Adamian et al., Int. J. Mod. Phys. E 5, 191 (1996).
2. T. Shneidman et al., Phys. Rev. C 65, 064302 (2002).
3. A. B. Migdal, The theory of finite Fermi systems and the properties of atomic nuclei, Moscow Izdatel Nauka (1983).
4. A. Bohr and B. R. Mottelson, Nuclear Structure (in 2 volumes), World Scientific Publishing Company, 1998.
5. S. G. Kadmensky et al., Phys. At. Nucl. 87, 359 (2024).
6. D.E. Lyubashevsky et al., arXiv preprint arXiv:2412.04410 (2024).
7. J. N. Wilson et al., Nature 590, 566 (2021).
8. J. Nix and W. Swiatecki, Nucl. Phys. A 71, 1 (1965).
9. D. E. Lyubashevsky et al., Chin. Phys. C 49, 044104 (2025).

Speaker: Dmitry Lyubashevsky (Voronezh State University)

43 Rotation Effect of a Fissile Nucleus (ROT Effect) for Prompt γ-Rays in Binary Fission of 235U by Polarized Neutrons of Different Energies

The present work provides a detailed examination of a series of studies [1,2] dedicated to investigating the effect of rotation of the fissile nucleus of the isotope $^{\text 236}$U in the $^{\text 235}$U(n,f) process induced by monochromatic polarized neutrons with energies of 62 meV and 270 meV. The main focus is on the analysis of the anisotropic angular distribution of γ-rays emitted by the excited fission fragments and its shift by a small angle relative to the deformation axis of the fissile nucleus when the neutron beam polarization direction is reversed.
The studied effect represents an important aspect in understanding the dynamics of the nuclear fission process, especially near the rupture point. The shift in the angular distribution of γ-rays can provide valuable information about the internal structure of fissioning nuclei and the mechanisms governing the fission process. This, in turn, may contribute to the development of a more comprehensive quantum-mechanical model of fission, which has yet to be established.
All experiments were conducted at the Heinz Mayer Leibniz Research Neutron Source (FRM II reactor) at the Technical University of Munich, located in Garching. A beam of polarized neutrons from the POLI facility was used for the measurements.
Additionally, the work includes a comprehensive analysis of results obtained in previous studies by the ITEP group [3] concerning ROT effects for fission γ-rays, which were obtained using cold neutrons. Furthermore, the results obtained by the PNPI group [4] for thermal neutrons are presented, allowing for a comparative analysis and the identification of common trends in the behavior of γ-rays under different experimental conditions.

Acknowledgment
This work was supported by the Committee of Science of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. BR21881930) and by the Russian Ministry for Science and Education, German Ministry for Education and Research BMBF through the project 05K13PA3. The instrument POLI is operated by RWTH Aachen in cooperation with JCNS FZ Jülich (Jülich Aachen Research Alliance JARA). We’re grateful to S. Masalovich, V. Hutanu, and J. Klenke for their help in setting up and conducting the experiment.
References
[1] Yu. Kopatch, V. Novitsky, G. Ahmadov, A. Gagarski, D. Berikov, G. Danilyan, V. Hutanu, J. Klenke, and S. Masalovich, EPJ Web Conf. 169, 00010 (2018).
[2] D. Berikov, G. Ahmadov, Yu. Kopatch, A. Gagarski, V. Novitsky, H. Deng, G. Danilyan, S. Masalovich, Z. Salhi, E. Babcock, J. Klenke, and V. Hutanu, Phys.Rev.C 104, 024607 (2021).
[3] G.V. Danilyan, J. Klenke, V.A. Krakhotin, Yu.N. Kopach, V.V.Novitsky, V.S.Pavlov, P.B.Shatalov, Phys. At. Nucl.74, 671 (2011).
[4] G.V. Valsky, A.M. Gagarski, I.S. Guseva, D.O. Krinitsin, G.A. Petrov, Yu.S. Pleva, V.E. Sokolov, V.I. Petrova, T.A. Zavarukhina, and T.E. Kuzmina, Bull. Russ. Acad. Sci. Phys. 74, 767 (2010).

Speaker: Daniyar Berikov (JINR)

44 Experimental Study on Differential Cross Section of 14N(n, p)14C Reaction

The report briefly outlines the significance and background of this experimental study, the experimental setup, and the preliminary results. The 14N(n,p)14C reaction is the most significant poisoning reaction in the s-process nucleosynthesis. The measurement of its differential cross-section is crucial for producing 19F, determining neutron dose in boron neutron capture therapy (BNCT), estimating spin-parity of nuclear energy levels, and testing some nuclear models. Currently, there are discrepancies between existing experimental data and evaluated data, and there is a lack of differential cross-section data across the entire energy range. This experiment was conducted at CSNS Back-n, aiming to provide a scientifically robust supplement to the controversies and gaps in the nuclear data of this reaction. The result obtained in this experiment represent the first differential cross-section result in this energy region. During the experiment, neutron beams irradiated targets such as aluminum-backed C3H3N6 and aluminum-backed 6LiF, with signals detected by silicon detectors and data acquired by waveform digitizing electronics. The report provides a detailed description and explanation of the data analysis process and experimental results. After data processing and R-matrix fitting, the differential cross-section measurements were found to be consistent with the JENDL-5.0 evaluation within the error margins. The fitting results were consistent with the measurements and showed a distinct angular distribution in the 2.2~5.5 MeV range. Additionally, resonance parameters for approximately 40 14N+n resonances in the 0.1~6 MeV range were obtained from the fitting results, including the spin-parity of the 15N compound nucleus excited states and the reaction widths of the 14N+n, 14C+p, 15N+γ, and 11B+α reaction channels.

Speaker: Qiuyue Luo (CSNS)

Experimental study on differential cross section of 14N(n,p)14C reaction_ISINN31.pptx

45 Double (n-γ) and Triple (n-n'γ) Angular Correlations in Neutron Inelastic Scattering on 12C

Understanding (n-γ) and (n-n'γ) correlations is crucial for analyzing inelastic neutron scattering processes and assessing the impact of direct and compound nucleus mechanisms on nuclear reactions. However, there are few experiments measuring (n-n'γ) correlations with 14 MeV neutrons, and most of these studies, conducted over 40 years ago, suffer from poor accuracy and limited angular range [1-5]. Recent measurements of (n-n'γ) correlations in the inelastic neutron scattering on $^{12}$C [6] show discrepancies with earlier results. Therefore, obtaining data with better statistics and higher angular resolution is of great interest.
At the TANGRA facility in Dubna, an experiment is underway to measure angular correlations (n-n'γ) in the inelastic scattering of 14.1 MeV neutrons on $^{12}$C using the tagged neutron method. The setup includes twelve 1-meter-long plastic scintillation detectors, each equipped with two photomultiplier tubes (PMTs). Ten detectors are positioned around the target in the reaction plane, while two are placed perpendicular to it. These detectors offer a time resolution of approximately 3 ns and a spatial resolution of about 20 cm, enhancing angular resolution and enabling the separation of gamma rays from neutrons based on their time-of-flight.
A theoretical approach is proposed to describe the double differential cross section of gamma radiation in inelastic neutron scattering. This approach considers the directions of the incident neutron, scattered neutron, and gamma quantum. It uses rotationally invariant functions of three vectors, as described in [7]. Our formula for angular correlations includes S-matrix elements, which can be obtained using the TALYS program for calculating nuclear reaction cross sections. Theoretical calculations were performed using the TalysLib library [8] to optimize the optical potential parameters. This was done to accurately describe the angular distribution of inelastically scattered neutrons.
Acknowledgment
The present research was supported by the Russian Science Foundation (grant No. 23-12-00239).
References
References
1. G. Deconninck, A. Martegani. Nucl. Phys. 1960. V. 21. P. 33-37.
2. B. A. Benetskii, I. M. Frank. JETP. 1963. V. 17/2. P. 309.
3. J. Zamudio, L. Romero, R. Morales. Nucl. Phys. 1967. V. A96. P. 449.
4. D. H. Spaargaren, C. C. Jonker. Nucl. Phys. 1971. V. 161/2. P. 354-374.
5. R. De Leo, G. D’erasmo, F. Ferrero, A. Pantaleo. Nucl. Phys. 1973. V. 212. P. 253-268.
6. K. J. Kelly, M. Devlin, J. M. O’Donnell, E. A. Bennett. Phys. Rev. C. 2021. V. 104. 064614.
7. L. C. Biedenharn, J. D. Louck. Encyclopedia of Mathematics and its Application; Ed. G. C. Rota,
V. 8. - Addison-Wesley Publishing Company Reading, Massachusetts, 1981.
8. N. A. Fedorov, New developments in TalysLib library, ISINN-29, 29.05-02.06.2023, Dubna.

Speaker: Polina Filonchik (JINR)

Filonchik_ISINN_2025.pptx

Parallel Session 2: Nuclear data for applied and scientific purposes/Neutron detection & Methodical aspects: (3)

Convener: Pavel Prusachenko (FLNP JINR)

46 The Reconstruction Algorithm for Neutron/Gamma Imaging Detectors Based on Artificial Neural Networks

Gamma and neutron imaging are crucial non-destructive testing techniques which have been widely used in nuclear safety, national security, materials characterization, and cultural heritage preservation. While the hit position reconstruction algorithms are key issues to improve the image fidelity and accuracy. A 2D planar neutron and gamma imaging system based on a monolithic lithium glass scintillator and a silicon photomultiplier (SiPM) array have been developed. To overcome the edge distortion of the traditional Center-of-Gravity (COG) reconstruction method, several distinct algorithms have been studied and compared, which including the Truncated COG (TCOG), the Particle Swarm-Optimized Least Squares Estimator (PSO-LSE) method and artificial neural networks (ANN) including fully connected neural network (FCNN), residual neural network (ResNet), and convolutional neural network (CNN).
The imaging performance have been evaluated using three metrics: flood image uniformity, useful field-of-view, and position linearity response. The result indicates that the ANN methods represent significant advancement over traditional reconstruction method and achieves better metrics values. These methods were used to reconstructed the images of the ‘720’ and ‘SCU’ models, and the imaging performance were quantitative evaluated by Contrast-to-Noise Ratio, Information Entropy, and Gradient Magnitude. The analysis demonstrates that the FCNN method exhibits best image quality. The spatial resolution were calculated using a knife-edge slit phantom by the modulation transfer function (MTF), and the MTF10 value of 0.45 mm have been achieved for the FCNN method. These methods have been applied on the experimental system, and validated by the flood image and pinhole image, which indicate the ANN models trained by the simulation data can be applied on the experimental data although some artifacts are introduced. This study demonstrates that ANN method significantly enhances both positioning accuracy and computational efficiency, ultimately resulting in superior quality for neutron/gamma imaging.
Acknowledgment:
Present study was supported by National Key R&D program of China (2023YFF0721700)

Speaker: Jifeng Han (Sichuan University)

47 Developing and Optimizing Signals Processing Techniques for the Tangra Project Experimental Setups

In the scope of the “TANGRA” (TAgged Neutrons and Gamma RAys) project established at the Frank Laboratory of Neutron Physics (JINR, Dubna), several experimental setups of different configurations [1] were devised and employed to study the inelastic scattering of neutrons with an energy of 14 MeV on atomic nuclei using the tagged neutron method [2].
One of “TANGRA” setups utilizes two high-purity germanium (HPGe) semiconductor detectors [3] to measure gamma-radiation resulting from the neutron-induced reactions. The selection of HPGe was made on the basis of its smaller band gap and the lowest energy for formation electron-hole pairs in comparison to other semiconductors.
In the “TANGRA” experiments, customized digitizers are employed, with the resulting signals subsequently fed into the “Romana” software, which was developed as a part of the project. The software is used for recording and processing of signals from the detectors, and it utilizes a specialized approach for acquiring spectrometric information.
Nevertheless, it has been observed that the energy resolution significantly deteriorates as the detector load increases. One potential solution to mitigate this loss of resolution is to expand the processing area of signals. However, this approach may cause the processing system to be unable to maintain the required data processing rate, potentially leading to data loss.
Consequently, alternative digital signal processing techniques were developed, and optimal parameters were identified to achieve the best energy resolution.
The purpose of this report is to present the findings from the latest studies on optimizing parameters for various methods used to process digitized signals from HPGe detectors.
Acknowledgment
This research was supported by the Russian Science Foundation under grant No. 23-12-00239.
References
1. TANGRA experimental setups, https://flnp.jinr.int/en-us/main/facilities/tangra-project-en
2. I.N. Ruskov, Yu.N. Kopatch, V.M. Bystritsky, et al. Physics Procedia, vol. 64, 2015,pp. 163-170, ISSN 1875-3892, https://doi.org/10.1016/j.phpro.2015.04.022
3. Yu.N. Kopatch, D.N. Grozdanov, N.A. Fedorov, et al. Moscow University Physics Bulletin, vol. 79, No 3, pp. 308-317, 2024. http://dx.doi.org/10.3103/s0027134924700437

Speaker: Petr Kharlamov (JINR)

Kharlamov_isinn31.pdf

48 Dataset Preparation Software for Training a Neural Network to Determine the Boundaries of Full Energy Peaks in Gamma Spectra

Gamma spectra processing is one of the most time-consuming stages of instrumental neutron activation analysis. Since spectra contain a large number of multiplets, their processing by classical mathematical methods leads to high uncertainty in the areas of full energy peaks. In this case, it is necessary to perform manual fitting of peak boundaries. This process is planned to be automated using a neural network. However, for its training dataset should be created.
The software for the boundaries of full energy peaks dataset preparation was designed. The development was carried out in the object-oriented programming language C# (.NET Framework 4.8.1) using API Windows Forms. To create a dataset, about 70000 gamma spectra were selected. In order to increase spectra processing performance, a flexible control system was introduced, allowing to work in the program in three modes: keyboard only, mouse only and keyboard + mouse. Additionally, vertical and horizontal zoom functions were added for more accurate processing. To access the application, the user authorization system was implemented via MS SQL Server, used to record the parameters of processed full energy peaks into the database.

Acknowledgment
The present study was supported by the AYSS JINR grant 24-401-02

Speaker: Vladimir Galustov (JINR)

49 (Withdrawn) Fast-Timing Measurement at CSNS

Fast-timing measurement of nuclear excited states using Labr3 detectors has gained a lot of attention in experimental nuclear physics. This is because that the lifetime information is more sensitive to the intrinsic nuclear structure than the level energy. In this talk the speaker will briefly introduce the idea of constructing a fast-timing detector array by LaBr3 detector coupled with digital DAQ system at CSNS and show some preliminary result.

Speaker: Guangxin Zhang (Sun Yat-sen University)

50 Compact Time-of-Flight Neutron Spectrometer with Digital Signal Processing

A compact time-of-flight neutron spectrometer was developed as a part of the BM@N setup at the Nuclotron accelerator (JINR). The aim of the spectrometer is study of neutron emission from target spectator decay in heavy-ion collisions at 2 – 4 A GeV. The neutron spectra are measured at large angles in the energy range of 2 – 200 MeV using small flight path of 20 – 30 cm. Neutron detectors are based on stilbene scintillators coupled with four silicon photomultipliers. The time and shape of detector pulses are processed and recorded using TQDC modules developed in JINR. The characteristics of the spectrometer were studied in the last BM@N run with Xe + CsI collisions at 3.8 A GeV. The obtained time resolution of the detectors is σt ≈ 110 – 120 ps. A high degree of gamma-quanta suppression was achieved by the pulse shape discrimination method with a factor FOM ≥ 2. A careful study of γ-ray and neutron background was an important part of the experiment. It was shown that the developed TOF spectrometer can provide reliable measurement of neutron spectra. An example of neutron energy spectrum obtained for Xe + CsI collisions is shown and discussed.

Speaker: Nikita Lashmanov (JINR)

Lashmanov_ISINN.pdf

51 Progress of Shielding Integral Experiments at China Institute of Atomic Energy

Beryllium, zirconium, and bismuth play crucial roles in nuclear science and technology: beryllium serves as a neutron reflector and moderator, zirconium is widely used in reactor structural materials, and bismuth is essential in accelerator-driven systems and lead-bismuth-cooled reactors. Accurate nuclear data for these materials are critical for shielding, reactor design, and nuclear safety assessments. To assess the reliability of nuclear data libraries, shielding integral experiments were conducted at the China Institute of Atomic Energy (CIAE) using the 400 kV nanosecond pulsed neutron generator. The experiments were performed on three different thicknesses of each material at six measurement angles, providing valuable benchmark data for the evaluation of CENDL-3.2, ENDF/B-VIII.0, JENDL-5, and JEFF-3.3.
To improve the accuracy of shielding integral experiments, several key optimizations were implemented. SiC detectors were introduced for associated particle detection, enabling simultaneous measurement of D-D and D-T neutron yields, which effectively resolved the issue of D-D reactions induced by deuterium deposition on the target. A monitor detector system was deployed at 0° and 90°, and its neutron time-of-flight spectra were analyzed using the MLEM algorithm, achieving a source neutron pulse time distribution precision better than 10-3. To validate the reliability of the experimental platform, polyethylene benchmark experiments were conducted at 47°, 61°, and 79° to examine the consistency of C/E values across different energy regions.
For beryllium, CENDL-3.2 demonstrated reasonable agreement with experimental data in the elastic scattering region, with minor overestimations observed at small angles. However, in the (n,2n) reaction region, significant deviations in spectral shape were present, particularly at larger angles. ENDF/B-VIII.0 and JENDL-5 provided good agreement at small angles but underestimated neutron spectra at larger angles. JEFF-3.3 consistently underestimated experimental results across all angular ranges, highlighting the need for further refinement in the (n,2n) reaction region.
For zirconium, CENDL-3.2 showed increasing C/E values with angle in the (n,el) region, underestimating at small angles and overestimating at large angles, while the other libraries remained stable but consistently overpredicted. In the (n,inl)D region, CENDL-3.2 and JEFF-3.3 overestimated at all angles, while ENDF/B-VIII.0 was notably lower. In the (n,inl)C region, JEFF-3.3 underestimated at large angles with decreasing cross-section values. In the (n,2n) region, CENDL-3.2 and JEFF-3.3 predicted lower neutron spectra than experimental results, with their cross-sections lower than ENDF/B-VIII.0 and JENDL-5.
For bismuth, CENDL-3.2 showed reliable performance across various scattering regions, particularly at intermediate angles. The discrete inelastic scattering region showed that JEFF-3.3 provided better agreement at small angles, whereas JENDL-5 was more accurate at larger angles. The continuous inelastic scattering region indicated that JEFF-3.3 provided the best overall agreement. ENDF/B-VIII.0 provided the closest agreement in the (n,2n) reaction region, while JENDL-5 demonstrated stable performance across multiple energy regions.
These results highlight the importance of continuous experimental validation for improving nuclear data libraries. The study provides valuable benchmark data for neutron transport simulations, shielding analysis, and nuclear reactor applications. Further refinements in nuclear models, particularly in the (n,2n) reaction region, are necessary to enhance the reliability of nuclear data for beryllium, zirconium, and bismuth.

Speaker: Shiyu Zhang (CIAE)

15:35 Coffee Break

Parallel Session 1: Fundamental interactions & symmetries in neutron induced reactions/Properties of compound states, nuclear structure/Intermediate and fast neutron induced reactions/Nuclear fission: (4)

Convener: Yonghao Chen (高能所)

52 Measurement of Neutron Total Cross Section of 169Tm at Back-n

The neutron total cross sections ( σtot ) are of great value in nuclear reactor design, nuclear theory models, nuclear applications and other fields. Thulium ( 169Tm ) is a crucial neutron absorbing material, and the σtot of 169Tm are highly useful for nuclear reactor design. However, there are only a few experimental σtot of 169Tm in EXFOR and no data in the energy between 10 keV and hundreds keV. Besides, the evaluated σtot of 169Tm in ENDF/B-VIII.1, JENDL, and TENDL show significant discrepancies within the 10 keV and 100 keV energy region. To determine the σtot of 169Tm in the energy between 10 keV and 100 keV, a wing-shaped lithium glass detector was designed in this work， and a measurement was carried out with this lithium glass scintillation detector at the Back-n facility. The experimental backgrounds induced by gamma rays were measured with lithium-7 enriched scintillator and “black resonance filter” method. The corrections for dead time, beam stability, and self-shielding were taken into consideration in the data analysis. The σtot of 169Tm in the energy between 5 keV and 100 keV was obtained and compared with the evaluated data from ENDF/B-VIII.1, JENDL, and TENDL. The comparison result indicated that the σtot of 169Tm measured by this work is more consistent with the evaluated data of JENDL-5.

Speaker: Jie Ren (China Institute of Atomic Energy)

53 Cross Sections of the 148Sm(n, α)145Nd Reaction in the 4.8–5.3 MeV Neutron Energy Region

Cross sections for the 148Sm(n,α)145Nd reaction were measured at neutron energies of 4.8, 5.1, and 6.3 MeV, performed at the EG-5 Van de Graaff accelerator at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research. A double-section gridded ionization chamber was employed to detect the emitted alpha particles. Samples of 148Sm2O3 were positioned back-to-back on the common cathode plate of the chamber. Monoenergetic neutrons were produced via the D(d,n)3He reaction in a deuterium gas target. The neutron flux was monitored with a 3He long counter, and the absolute flux was determined using a 238U3O8 sample. The experimental results are compared with evaluated data and calculations from the TALYS-1.96 nuclear reaction code.

Speaker: Igor Chuprakov (JINR)

Chuprakov_148Sm(n,α)145Nd reaction_ISINN_31_2025.pdf

54 Measurement Thermal Neutron Capture Cross Section and Resonance Integral of 94Zr(n, γ)95Zr Reaction using Intense Resonance Neutron Source “IREN’’

The thermal capture cross section and resonance intergal for the 94Zr(n,γ) reaction were measured relatively to that of 197Au(n,γ)198Au by activation method using IREN facility of the Joint Institute for Nuclear Research (JINR) [1]. Neutrons are produced via the interaction of electron beam with a tungsten target. The induced activities in activated samples were measured by a high-resolution HPGe gamma spectrometer. The necessary correction factors including neutron thermal and epithermal self-shielding effects, the γ-ray self-absorption and other were taken into account to improve the accuracy of the results [2]. Our obtained value of thermal neutron cross-section for 94Zr(n,γ)95Zr reaction is 0.0516 ± 0.00395 barn. The differences between this value and most of that listed in the international nuclear data libraries JENDL-4.0, JEFF-3.2, ENDF/B-VII.1 are less than 4%. The value of the resonance integral measured by us is 0.2764 ± 0.084 barn, which is 14% difference from the mean of previously reported data.

Speaker: Le Tran Minh Nhat (JINR)

55 Recent Progress of Neural Networks in Nuclear Structures

In the burgeoning age of artificial intelligence (AI) and advanced technologies, neural networks have emerged as powerful tools, revolutionizing various scientific domains. This lecture, "Recent Progress of Neural Networks in Nuclear Structures," explores the intricate workings of these algorithms and their transformative impact on nuclear physics.
We begin by examining the fundamental principles that underpin neural networks and their learning processes, drawing from seminal works such as V. Vapnik's "The Nature of Statistical Learning Theory" [1]. This foundational understanding sets the stage for our exploration into the application of neural networks in nuclear physics. The lecture introduces recent advancements in machine learning (ML) techniques tailored for nuclear physics, as discussed in Boehnlein et al.'s comprehensive review, "Colloquium: Machine Learning in Nuclear Physics" [2]. We highlight how these ML algorithms accelerate complex calculations, offering unprecedented efficiency and accuracy. A significant portion of the lecture is dedicated to the application of ML in predicting nuclear masses, a critical area of research. We reference Mumpower et al.'s work on "Physically Interpretable Machine Learning for Nuclear Masses" [3], which highlightes the potential of ML in enhancing our understanding of nuclear structures.

Furthermore, we extend our discussion to the prediction of ground-state charge radii using support vector regression, as demonstrated by Jalili and Chen [4]. Additionally, we explore the application of ML in predicting alpha and beta decay, with research on "Nuclear Beta-Decay Half-Life Predictions and r-Process Nucleosynthesis Using Machine Learning Models" [5]. Through these discussions, the lecture underscores the pivotal role of neural networks in advancing nuclear physics, paving the way for future innovations and discoveries.
References:

[1] V. Vapnik, The Nature of Statistical Learning Theory (Springer Science and Business Media, 1999).
[2] Boehnlein, A. et al. Colloquium: Machine learning in nuclear physics. Reviews of Modern Physics 94, 031003 (2022).
[3] Mumpower, M., Sprouse, T., Lovell, A. and Mohan, A. Physically interpretable machine learning for nuclear masses. Physical Review C 106, L021301 (2022).
[4] Jalili, A. and Chen, A.-X. Prediction of ground state charge radius using support vector regression. New Journal of Physics 26, 103017 (2024).
[5] Jalili, A., Pan, F., Luo, Y. and Draayer, J. P. Nuclear beta-decay half-life predictions and r-process nucleosynthesis using machine learning models. Physical Review C 111, 034321 (2025).

Speaker: Amir Jalili (Zhejiang Key Laboratory of Quantum State Control and Optical Field Manipulation, Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China)

Parallel Session 2: Nuclear data for applied and scientific purposes/Neutron detection & Methodical aspects: (4)

Convener: Jifeng Han (四川大学)

56 Characterization of an EJ-200 Plastic Scintillator Array for Experiments with 14-MeV Tagged Neutrons Using Carbon and Polyethylene Samples

The main goal of the TANGRA (TAgged Neutrons and Gamma RAys) project at the Frank Laboratory of Neutron Physics (JINR, Dubna) is to study the interaction of 14.1 MeV neutrons with various nuclei. One of the experimental setups developed within the project consists of an array of 20 EJ-200 plastic scintillators and is designed to study the angular distributions of neutrons and γ-rays resulting from the elastic and inelastic scattering of 14.1 MeV neutrons. The motivation for this work is the problem of computational and experimental determination of the detection efficiency of organic scintillation detectors for neutron energies above 8 MeV. In particular, the issue of simulating the efficiency of EJ-200 scintillators arises from contradictory and insufficient data regarding the light output functions for secondary charged particles emitted during neutron interactions with this scintillator material. Another pressing issue is the development of novel methods for the experimental verification of the detection efficiency of neutron detectors used in tagged neutron beam experiments.
To resolve these issues the energy dependence of the light output for secondary charged particles (protons and α-particles) was measured in the neutron energy range of 1.5 to 14.0 MeV for an array of EJ-200 scintillation detectors. The scattering of a tagged neutron beam with an energy of 14.1 MeV on graphite and polyethylene samples was used to obtain neutrons with known energies at various angles. Based on the obtained data, both the response function and the intrinsic efficiency of the detectors used were simulated in GEANT4. To verify the simulated efficiency, a method based on the measurement of elastically scattered neutrons from the 1H(n,n0)1H reaction was implemented.

Acknowledgment

The present study was supported by the Russian Science Foundation (grant no. 23-12-00239).

Speaker: Pavel Prusachenko (JINR)

prusachenko_ISINN31.pdf

57 Constrained Optimization of Microscopic Nuclear Data via Integral Experiment-Informed Frameworks

Current microscopic nuclear data face two major challenges: significant discrepancies among datasets from different sources and missing data points at specific energy levels. To maximize the utilization of existing data, this study proposes constraining differential experimental results through integral experiments, thereby enhancing data consistency and completeness.
Our investigation focuses on two microscopic physical quantities: fission yields and the Prompt Fission Neutron Spectrum (PFNS). In fission yield research, leveraging the analytical strengths of machine learning in complex data processing, we employ a Bayesian Neural Network (BNN) to model experimental data on neutron-induced 239Pu fission yields. The objective is to uncover latent energy-dependent correlations and establish an energy dependence framework. For optimizing the PFNS, we developed a random sampling methodology. The proposed methodology begins with generating PFNS candidate sets through randomized sampling that incorporates microscopic experimental measurements and their uncertainty ranges, followed by full-core neutron transport simulations using the JMCT code for critical benchmark configurations under these sampled PFNS conditions. The PFNS is then iteratively optimized through systematic comparison between calculated effective multiplication factors keff and experimental benchmark values, thereby establishing a self-consistent framework bridging microscopic data uncertainties and macroscopic reactor physics.
Acknowledgment
Present study was supported by the National Natural Science Foundation of China (No.12347126)

Speaker: Jiahao Chen (Institute of Applied Physics and Computational Mathematics)

58 (Withdrawn) Progress in Measurement of the Capture Reaction Cross Section of 242Pu Induced by Thermal Neutron Based on Activation Method

The relative deviation of the thermal capture cross-section of 242Pu in the mainstream nuclear database is more than 10%, and the uncertainty of its capture cross-section in the intermediate and fast neutron region is over 30%. In this paper, the thermal capture cross-section measurement of 242Pu was carried out based on activation method. The irradiation experiment was carried out on the running-rabbit irradiation channel of Xi'an pulse reactor. The neutron flux was measured with the thermal capture cross section of 197Au. The capture reaction product 243Pu was analyzed by the γenergy spectrum, and 243Am was analyzed by mass spectrometry. The thermal capture cross-section obtained byγenergy spectrum analysis are 21.12 ± 2.36b. Mass spectrometry experiments and data processing are being carried out. The main contributions of the uncertainty of that are the peak counts and branch ratio of 84keV of 243Pu.The next step is to optimize the matrix material and shielding method of the sample, and to carry out the measurement of 243Pu characteristic ray branch ratio based on the combined analysis of mass spectrometry and energy spectrum, so as to reduce the uncertainty of thermal capture cross-section based on the γspectrum analysis.

Speaker: Yonggan Zhang-Sun (NINT)

59 Upgrade Plan for Spallation and Transmutation Reaction Models in ADS Studies

In accelerator-driven subcritical nuclear system (ADS) simulations, spallation and transmutation reaction models are typically employed due to the lack of the database in medium-to-high energy range. However, some model deviations have been identified, particularly in high-energy neutron-induced reactions on actinide nuclides. This paper presents a comprehensive verification of the current intranuclear cascade model and de-excitation models in terms of the differential cross-section data. Furthermore, we propose an upgrade plan for the spallation and transmutation reaction models by incorporating nuclear medium effects and nucleon-nucleon short-range correlations, which are currently missing in the existing Monte Carlo simulation framework. These model improvements are expected to enhance the accuracy of full-energy range and multi-particle Monte Carlo transport simulations, thereby advancing the ADS research and design and many other simulation studies in medium-to-high energy region.

Speaker: Rong Wang (IMP, CAS)

Poster Session

18:30 Dinner

Wednesday, 28 May

Tour

60 CSNS tour

12:30 Lunch

61 City tour (Keyuan Garden)

18:00 Banquet

Thursday, 29 May

Parallel Session 3: Neutron detection & Methodical aspects/Physics of ultracold neutrons: (1)

Convener: Maxim Zakharov (Joint Institute for Nuclear Research)

62 Recent Progress of the Physical Design for the Ultra-Cold Neutron Source at CSNS

Recent progress of the phycical design for the the Ultra-cold Neutron Source at CSNS

Speaker: Tiancheng Yi (CSNS)

63 Concept of the UCN Source at the WWR-K Reactor (AlSUN)

A concept is presented for an ultracold neutron (UCN) source with a superfluid helium converter placed in the thermal column of the WWR-K research reactor (Almaty, Kazakhstan). Similar source designs are employed in the existing TRIUMF project (Vancouver) [1] and the proposed project at the WWR-M reactor (Gatchina) [2]. The main distinguishing features of our concept are more efficient systems for accumulating UCNs in the source and transporting them to experimental facilities. This is achieved by separating the heat and UCN fluxes from the source, as well as by lowering the temperature of the helium converter below approximately 1 K.
In this work, we build on the parameters of UCN source concepts from existing projects that involve accumulating UCNs in superfluid helium, and we aim to refine these parameters for developing a UCN source at the WWR-K reactor. We perform an assessment of the achievable UCN density both in the source and in the experimental setup. We also discuss the challenges that must be resolved to justify the feasibility of such a project and to achieve the highest possible performance of the source.

Acknowledgment
This work was carried out with the financial support of the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan as part of the grant-funding program for young scientists under scientific and technical projects No. AP19579042.

References

[1] J. Martin, B. Franke, K. Hatanaka, S. Kawasaki, and R. Picker, The TRIUMF UltraCold Advanced Neutron Source // Nucl. Phys. News 31, 19 (2021).
[2] Serebrov A. P., Fomin A.K., Kharitonov A. G. et al. High-Density Ultracold Neutron Sources for the WWR-M and PIK Reactors // Cryst. Rep. 2016. V. 61. P. 144.

Speaker: Kylyshbek Turlybekuly (JINR)

64 Calculation for Improving the Efficiency of Ultracold Neutron Transport Using Monte Carlo Method

The development of intense low-energy neutron sources requires extensive calculations to refine the design to meet practical needs. With the appearance of liquid helium-based ultracold neutron sources (UCN), from which all UCN can be released through a small outlet, it became possible to use a new type of mirror neutron guides. They consist of three main parts: a short expanding part, a long parallel part, and a short tapering, focusing part. This research has shown that such neutron guides reduce UCN losses during transportation several times and increase the UCN density at the outlet several times, compared to traditional parallel neutron guides. The research was conducted using the GEANT4 simulation toolkit [1-4]. Such a neutron guide can be used in the design of the ALSUN UCN source at the Institute of Nuclear Physics in the Republic of Kazakhstan [5].
References
[1] Recent Developments in Geant4, J. Allison et al., Nucl. Instrum. Meth. A 835 (2016) 186-225.
[2] Geant4 Developments and Applications, J. Allison et al., IEEE Trans. Nucl. Sci. 53 (2006) 270-278.
[3] Geant4 - A Simulation Toolkit, S. Agostinelli et al., Nucl. Instrum. Meth. A 506 (2003) 250-303.
[4] F. Atchison, T. Brys, M. Daum, P. Fierlinger, A. Fomin, R. Henneck, K. Kirch, M. Kuzniak, A. Pichlmaier, Nucl. Instrum. Methods A 552, 513 (2005).
[5] Turlybekuly K., Shaimerdenov A.A., Sairanbayev D.S., Shapiro D., Mukhametuly B., Bayakhmetov O., Sakhiyev S.K. Calculation of neutron and gamma fields in the niche of the thermal column of the WWR-K research reactor, considered as the location of the ultracold neutron source. NNC RK Bulletin. 2024;(3):49-55.

Speaker: Khac Tuyen Pham (Joint Institute for Nuclear Research)

65 Modeling and Optimization of Experimental Setup Geometry for Measuring Ultracold Neutron Loss Factors Using Gravitational Spectroscopy

This study presents numerical and analytical investigations aimed at optimizing the measurement of ultracold neutron (UCN) loss factors on various materials using the gravitational [1] spectroscopy method. The optimization of experimental setup geometry was performed through numerical simulations, allowing for the determination of optimal parameters to enhance measurement accuracy. Within the UCN gas [1] model framework, time dependencies of storage, filling, and emptying of neutron vessels were calculated, and measurement uncertainties for UCN loss factors were evaluated for different materials (deuterated polyethylene, diamond-like carbon, and beryllium). Estimated exposure times were obtained, and the dependence of statistical data collection time on the sample surface area was analyzed, enabling the determination of optimal experimental conditions. The results of this study can be utilized to improve the precision and efficiency of experiments investigating ultracold neutron interactions with surfaces.

Speaker: Zhanibek Kurmanaliyev (JINR)

66 Experimental Validation and Geant4 Simulation of Spatial Resolution in Fast Neutron Radiography at CSNS Back-n Facility

Fast neutron radiography offers distinct advantages over conventional X-ray radiography, demonstrating significant developmental potential and broad application prospects in strategic fields including national defense, aviation, aerospace, and nuclear energy. As a critical performance indicator for imaging systems, spatial resolution has been extensively studied through theoretical simulations in current research, while experimental investigations remain comparatively limited.
This study develops a comprehensive simulation methodology for system spatial resolution using Geant4 Monte Carlo simulations, complemented by systematic experimental validation at the Back-n white neutron source facility of the China Spallation Neutron Source (CSNS). The experimental results exhibit close agreement with theoretical predictions, thereby establishing crucial technical foundations for advancing fast neutron radiography applications. This work bridges the gap between simulation and experimental research while providing valuable insights for optimizing imaging system performance in practical implementations.

Speaker: Baojun Duan (NINT)

Parallel Session 4: Nuclear and related analytical techniques in environmental and materials science: (1)

Convener: Manh Dung Ho

67 Air Pollution Studies in Asia and the Pacific Based on Moss Analysis by Nuclear and Related Analytical Techniques

Air pollution is the world's most pressing environmental crisis It is responsible for more than 7 million deaths annually, the bulk of which – 70 per cent – occurs in Asia-Pacific region. Air pollution in these countries is several times higher than WHO guideline for safe air. Heavy metals (HM) are among the most dangerous environmental pollutants. In most European countries, the need to study the consequences of their impact on the environment and human health has led to the establishment of national and international programs for biomonitoring of heavy metal atmospheric deposition. Data on atmospheric deposition of HM and other toxic elements obtained on the basis of analysis of moss biomonitors, which serve as an analog of aerosol filters. Under the auspices of the United Nations Commission on UNECE Convention on Long-range Transboundary Air Pollution (UNECE ICP Vegetation), the Atlases (Reports) of Atmospheric Deposition of Heavy Metals are published every five years. Since 1995, the international team of the JINR FLNP Sector of Neutron Activation Analysis and Applied Research has been contributing to these Atlases. Study of atmospheric deposition of heavy metals and other toxic elements in a number of JINR member and non-member states made it possible to identify and assess the areas of these pollutions in the studied territories and compare with the levels of similar pollution in Western Europe.
The possibility of extending our experience to Asia-Pacific countries is currently being discussed with representatives of several countries in this region in January 2025 at an online workshop organized by JINR. Some examples of our previous research on deposition of trace elements in China in 2002 [2] are cited to draw the attention of Chinese scientists to our cooperation in studying air pollution in the Asia-Pacific region.
References
1. M. Frontasyeva, H. Harmens, A. Uzhinskiy, O. Chaligava and participants of the moss survey (2020). Mosses as biomonitors of air pollution: 2015/2016 survey on heavy metals, nitrogen and POPs in Europe and beyond. Report of the ICP Vegetation Moss Survey Coordination Centre, Joint Institute for Nuclear Research, Dubna, Russian Federation, 136 pp. ISBN 978-5-9530-0508-1. http://www1.jinr.ru/Books/Books_rus.html

1. J. Shao, Z. Zhang, Z. Chai, X. Mao, Y. Lu, O. Stan, M.V. Frontasyeva, P. Wu. Study of concentration of heavy metals deposited from atmosphere by mosses. Journal of Nuclear and Radiochemistry, Vol. 24, No. 1, 2002, p. 6-11 (in Chinese).

Speaker: Marina Frontasyeva (JINR)

68 Risks Assessment of Gold Nanoparticles Exposure for the Soil-Plant-Consumer System

Extensive production and application of gold nanoparticles leads to contamination of aquatic and terrestrial ecosystems, creating risks for consumers of plant products. The effects of gold nanoparticles in concentration range of 1-100 mg/L applied in two routes on Mentha spicata L. plants, soil and human health was investigated. k0-neutron activation analysis was used to determine gold content in soil and plant segments and atomic absorption spectroscopy to determine its concentration in herbal remedy. Plants watering with 100 mg/L of gold nanoparticles contributed to accumulation of gold in soil (up to 1769 mg/kg) and root system (up to 454 mg/kg) and reduced the activity of soil microbiota by 28% compared to the control. Foliar application resulted in maximum gold uptake by leaves (552 mg/kg) and stems (18.4 mg/kg). Nanoparticles affected the content of chlorophyll and carotenoids in Mentha spicata L. leaves and led to an increase in antioxidant activity. High gold extraction from leaves into infusion indicates a risk of trophic transfer, and decreased soil microbiota activity points at the potential harmful effect of nanoparticles.

Speaker: Alexandra Peshkova (JINR)

69 Assessment of the Recreational Zones in Moscow Using Neutron Activation Analysis and Atomic Absorption Spectrometry

Instrumental neutron activation analysis was used to determine the content of more than 30 chemical elements in moss, soil and leaves samples collected in seven Moscow parks, Russia. To determine Cd, Pb and Cu atomic absorption spectrometry was applied. In general, in moss samples used to assess air pollution the content of elements increased with exposure time, except alkali element (K, Cs and Rb) which content decreased, probably due to pollutants impact. In leaves the highest content of elements was observed at the end vegetation period, that may be associated with processes in plants which promote elimination of toxic elements. In some soil samples was revealed excess of As, Zn and Cd. According to calculated total pollution index, the highest values was observed for soil, that can be associated with their ability to accumulate pollutants emitted by aerotechnogenic way for a longer period.

Speaker: Margarita Shvetsova (JINR)

70 Experimental Demonstration of Fast Neutron Absorption Spectroscopy Driven by Repetitive Laser Neutron Source

Hao Xu1, Jie Feng1,2, Mingyang Zhu1, Bingzhan Shi1, Guoqiang Zhang3, Jinguang Wang4, Yifei Li4, Xin Lu4,5,6, Wenchao Yan1,2, Liming Chen1,2
1State Key Laboratory of Dark Matter Physics, Key Laboratory for Laser Plasmas (MoE), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China, haoxu001@sjtu.edu.cn.
2 Collaborative Innovation Center of IFSA, Shanghai Jiao Tong University, Shanghai 200240, China.
3Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China.
4Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
5School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
6Songshan Lake Materials Laboratory, Dongguan 523808, China.

Fast neutron absorption spectroscopy enables isotope-specific material analysis with deep penetration and high nuclear sensitivity. However, achieving high-resolution, table-top fast neutron absorption spectroscopy remains challenging, primarily due to constraints in neutron time duration and diagnostic capability. Here, we report the first experimental demonstration of fast neutron absorption spectroscopy using a repetitive laser driven neutron source. With single-neutron counting and pulse shape discrimination techniques, we achieved high-precision, high-resolution (0.02 MeV at 0.5 MeV) neutron spectrum measurements. Magnesium resonance absorption features at 0.268 MeV and 0.432 MeV were clearly resolved. Local Pearson correlation analysis confirmed good agreement of experimental result and theoretical model. This work combines the ultrashort, table-top laser driven neutron source with advanced detection technique, opening a new avenue for non-destructive testing application and fundamental nuclear science.

Speaker: Hao Xu (Shanghai Jiao Tong University)

71 Neutron Spectra and Fast Neutron Fluence Rate Measurement for the Atomospheric Neutron Irradiation Spectrometer at CSNS

Neutron spectra and fast neutron fluence rate measurement for the Atomospheric Neutron Irradiation Spectrometer at CSNS

Speaker: Bin Zhou (CSNS)

10:20 Coffee Break

Parallel Session 3: Neutron detection & Methodical aspects/Physics of ultracold neutrons: (2)

Convener: Tiancheng Yi

72 Neutron Dispersion Law for Matter Moving with Acceleration

The report is devoted to the problem of interaction of slow neutrons with matter moving with acceleration. The possibility of transformation of the neutron dispersion law due to the general effect of acceleration is considered. The Acceleration effect consists of that the result of the interaction of a particle with any object moving with acceleration should be a change in its frequency ω and energy E=ħω. This change in frequency is determined by relation ∆ω≈kaτ, where k is the wave number, a is the object acceleration and τ - interaction time.
The effect was investigated in an experiment [1] in which neutrons were observed passing through a sample moving with acceleration. The experimental results were in a quite well agreement with theoretical estimates, but the estimates were based on an assumption that dispersion theory is valid in the case of accelerated matter, which is not obvious.
Furthermore, there are theoretical estimates of acceleration at which phenomena associated with neutron wave re-scattering in matter become significant for the theory of dispersion [2]. At the same time the results of [3, 4] allow to suggest that the energy changes should take place by a single scattering on an accelerated nucleus.
In connection with the above, the calculation of corrections to the neutron dispersion law in the case of accelerated matter and the analysis of the possibility of their experimental observation becomes relevant. The report presents possible ways to solve this problem.

References
1. A.I. Frank, P. Geltenbort, M. Jentschel, et al., Phys. of At. Nuc., 71, 1656 (2008).
2. A.I. Frank, Phys. Part. Nuclei 47, 647–666 (2016).
3. A.I. Frank, Physics-Uspeckhi, 63, 500-502 (2020).
4. M.A. Zakharov, G.V. Kulin and A.I.Frank, Eur. Phys. J. D 75, 47 (2021).

Speaker: Maxim Zakharov (Joint Institute for Nuclear Research)

73 Optimisation of Bulk Density of Nanodispersed Medium to Maximise Its Reflectivity for Very Cold Neutrons

Nanodispersed media, such as nanodiamond powders, are efficient diffuse reflectors of low-energy neutrons [1]. This is due to the intense coherent elastic scattering of such neutrons on individual nanoparticles of a few nanometers in size. Such reflectors can be used for quasi-specular reflection of cold neutrons [2] and in the design of very cold neutron sources for their directed extraction [3]. However, the influence of the bulk density of the nanodispersed medium (packing coefficient) on the reflection efficiency has not yet been studied.
The point is that the transport cross-section for very cold neutrons, which determines the reflectivity of the nanodiamond powders of finite thickness, should increase as the packing factor of nanoparticles in the volume increases. Nevertheless, with a significant increase in the packing factor, when the nanoparticles in the medium are so close together that neutrons can no longer scatter on them independently, the transport cross-section should start to decrease [4]. Theoretically, it should fall to almost zero and be determined only by incoherent scattering on individual nuclei in the case where the nanoparticles completely fill the entire available volume, since the fluctuations of the medium density, on which coherent scattering occurs, disappear.
The change in small-angle neutron scattering intensities with increasing media density has previously been observed when studying the fractal structure of unmodified nanodiamond powders produced by detonation synthesis [5-7]. Predominantly diamond nanoparticles in such powders form unbreakable primary clusters up to 100 nm in size, which do not allow achieving significant powder compaction. In practice, the bulk density of unmodified powders reaches 0.2 – 0.3 g/cm3.
In our study, to verify the influence of bulk density on the transport cross-section and reflection of very cold neutrons, we used deagglomerated nanodiamond powder, in which the nanoparticle clusters are almost completely destroyed, and the bulk density reaches 0.6 – 0.9 g/cm3 [8]. Total cross-sections and small-angle scattering intensities of thermal neutrons were measured at the YuMO small-angle scattering facility of the IBR 2 pulsed research reactor at the Joint Institute for Nuclear Research. The experimental results will be presented and discussed.
The study was initiated under grant ANR-20-CE08-0034, France.

References
[1] Bosak A. et al. Materials 13, 3337 (2020).
[2] Bosak A. et al. Materials 16, 703 (2023).
[3] Chernyavsky S.M. et al. Rev. Sci. Instrum. 93, 123302 (2022).
[4] Nezvanov A.Yu. Ph.D. thesis, Communauté Université Grenoble Alpes (2018).
[5] Avdeev M.V. et al. Diam. Relat. Mater. 16, 2050 (2007).
[6] Bulavin L.A. et al. Ukr. J. Phys. 66, 635 (2021).
[7] Tomchuk O.V. et al. Fuller. Nanotub. Carbon Nanostructures 30, 171 (2022).
[8] Aleksenskii A. et al. Nanomaterials 11, 1945 (2021).

Speaker: Alexander Nezvanov (JINR)

74 Universal Cryogenic Moderator for Research Neutron Sources of Any Power and Intensity

For the first time, the author proposed the concept of a new direction in the field of cold (cryogenic) neutron moderators for research neutron sources of low, medium and high power and intensity, which is based on the use of a universal cryogenic neutron moderator based on hydrocarbons. It is shown that the successful development of fundamentally new methods, installations, devices and facilities in the field of this direction will make it possible to get high-intensity beams of cold neutrons based on any research neutron source.

Speaker: Maksim Bulavin (JINR)

75 VCN Test Facility as the Initial Phase of the UCN Facility Development

A new high-brilliance ultracold neutron (UCN) source is planned to be created for the FLNP JINR pulsed reactor. It is planned to carry out a series of investigations using VCNs, which are essential for the design of the main elements of this UCN source. For this purpose, a test VCN channel at the third channel of the IBR-2M reactor will be built. This will allow us to obtain a VCN beam with a wide range of velocities. It has been estimated that the flux of desired neutrons with velocities of $20 \pm 1 $ m/s will be approximately $10^5$ n/s in ideal case. The source will be operational for a relatively long period of work on the project and will be replaced by the main source at the end. The report is devoted to the design of the VCN test channel.

Speaker: Alexander Popov (JINR)

76 Physical Design and Simulation of a Fission Spectrometer Based on the Velocity-Kinetic Energy Method

The investigation of neutron-induced fission independent yields of actinides is critically important for both the efficient utilization of nuclear energy and nuclear physics research. The fission spectrometer based on the velocity-kinetic energy method consists of a Time Of Flight (TOF）detector and a Frisch-Grid Ionization Chamber (FGIC), achieving mass yield distribution with a mass resolution less than 1 amu. This presentation focuses on the physical design and simulation studiy of the fission spectrometer. The Micro Channel Plate (MCP) time detector, which constitutes TOF, maintains secondary electron flight time spread of 50 ps and the flight distance is 70 cm. The FGIC operates with isobutane as the working gas, operating at an optimal E/P of 6 V/(cm·Torr) and a pressure of 5000 Pa. When the energy resolution is less than 0.8 % for light fragments and 0.6 % for heavy fragments, the mass resolution can be less than 1 amu. Based on the physical design, fission data for 14 MeV neutron-induced 238U was simulated by coupled calculations using Geant4, COMSOL and Garfield++. The mass yield distribution was calculated by the energy loss correction method. A measurement method for charge yield distribution based on K-means clustering algorithm is proposed, and the Root Mean Square Error (RMSE) and Error Ratio (ER) of the charge yield distribution are 6.36E-6 and 29.26%.The simulated independent yield distribution demonstrate agreement with the ENDF/B-VIII data. The physical design and simulation studies provide a foundation for future fission physics experiments.

Speaker: Jun Ma (Lanzhou university)

77 Parameters of Extracted Neutron Beams of the IREN Resonance Neutron Source at the FLNP, JINR

There are several instruments on the flight bases of the IREN facility that are used to carry out measurements on the transmission, capture and scattering of neutrons on samples.
The analysis of experimental data, the assessment of the possibility of conducting, and the planning of experiments with IREN beams require knowledge of the facility parameters: the absolute fluxes of resonance and thermal neutrons at the sample locations, the dependence of the neutron fluxes on the neutron energy, and the energy resolution function of the instruments.
The fluxes of thermal and resonance neutrons, the dependence of the neutron flux on their energy, and the resolution function were determined experimentally for 11-meter and 60-meter bases (on channels 4 and 3) of the IREN facility, JINR. The experimentally determined parameters are compared with the results of Monte Carlo calculations.

Speaker: Almat Yergashov (JINR)

78 Physical Design of PGAA and NDP for CSNS

Physical design of PGAA and NDP for CSNS

Speaker: Songlin Wang (CSNS)

79 Energy Distributions and Absolute Yields Measurements of the Long-Range Alpha Particles and the Tritons in Thermal Neutron-Induced Ternary Fission of 235U Using a Twin-Gridded Ionization Chamber

The energy distributions and absolute yields of the long-range alpha particles and the tritons in thermal neutron induced ternary fission of 235U were measured using a twin-gridded ionization chamber. The experimental result shows that the long-range alpha particles and the tritons can be separated obviously in the cathode amplitude vs anode amplitude two-dimensional spectrum, and the absolute yield of the long-range alpha particles can be obtained accurately by selecting the event region, and the yield is (1.84 ± 0.10) × 10-3. For the tritons, the tritons can be distinguished from the long-range alpha particles in the anode amplitude vs anode rime time two-dimensional spectrum, but the yield of the tritons needs to be corrected after considering the influence of the long-range alpha particles. The absolute yield of the tritons is (1.13 ± 0.06) × 10-4. The energy distributions of the long-range alpha particles and the tritons were determined by adjusting the mean energy and the FWHM of these particles to make sure that the simulated energy distributions are in good agreement with the experimental result. These results are discussed and compared with previous data.

Speaker: Zepeng Wu (Peking University)

Parallel Session 4: Nuclear and related analytical techniques in environmental and materials science: (2)

Convener: Marina Frontasyeva (JINR)

80 Development and Application of k0-standardized Neutron Activation Analysis Utilizing Short-Lived Radionuclides at the Dalat Research Reactor

An optimized k₀-neutron activation analysis (k₀-NAA) method, incorporating cyclic irradiations of short-lived radionuclides (SLRNs), was developed at the Dalat Research Reactor (DRR). This study presents the precise characterization of reactor parameters using a fast irradiation facility, rigorous sample preparation, and advanced calibration of HPGe detector-based gamma-ray spectrometry for accurate element quantification. Utilizing SLRNs (⁷⁷ᵐSe, ¹¹⁰Ag, ²⁰F, ¹⁷⁹ᵐHf, ⁵¹V, ⁴⁶ᵐSc), with half-lives ranging seconds to minutes, we targeted elements crucial for biological and environmental studies. The “k0-Dalat” software, a home-made with highly automated capability, facilitated rapid analysis within a single workday. The method’s accuracy was validated using certified reference materials (SMELS-I, NIST-SRM-1566b, NIST-SRM-2711a), demonstrated accuracy within 5-8% of certified values, with detection limits of 0.2-1.9 mg/kg for elements of interest in biological samples, confirming the method’s high sensitivity and applicability for similar matrix analyses.

Speaker: Manh Dung Ho (Center for Nuclear Technologies, Vietnam Atomic Energy Institute)

81 Development Status of the Neutron Detectors for Instruments at China Spallation Neutron Source

Development status of the neutron detectors for instruments at China Spallation Neutron Source

Speaker: Jianrong Zhou (CSNS)

82 In Situ Neutron-Diffraction Studies of Structural Phase Transitions in Fe-xGa Alloys

It is already well known that Fe-Ga alloys possess increased values of the magnetostriction constant. This characteristic has been studied in a wide range of gallium concentration (up to 35 at.%) [1, 2] and the presence of two peak of magnetostriction at 19 and 27 at.% of gallium has been established. At present, work is underway to analyze the influence of certain structural phases on the magnetostrictive properties of Fe-Ga alloys, including the influence of metastable pseudocubic phases, which can form already at gallium concentration of 27 at.% [3]. Therefore, the identification of general regularities of metastable phases and their transition to equilibrium phases is an important step in the development of the scientific basis for the formation of the optimal structural-phase state of Fe-Ga alloys in terms of their functional characteristics.
The use of neutron diffraction eliminates the influence of surface effects and local inhomogeneities of the structure on the experimental data. Also, the possibility of studying samples of large sizes minimizes the influence of coarse-grained structure on the diffraction patterns. Therefore, neutron diffraction is a very effective method for studying phase transitions in Fe-Ga alloys. In addition, the High-Resolution Fourier Diffractometer (IBR-2 pulsed reactor in JINR, Dubna, Russia) and General Purpose Powder Diffractometer (China Spallation Neutron Source, Dongguan, China) used by us made it possible to carry out in situ experiments with the data acquisition rate at the level of several minutes. This allowed us to analyze in detail the structural changes during continuous heating and isothermal exposures.
In situ comparative studies of the phase composition evolution during continuous heating of the Fe68Ga34 alloy, characterized by different initial states, were carried out. In addition, the kinetics of phase transformations in this alloy was studied under conditions of long-term isothermal exposure at temperatures of 360-600 °C. Details of the experiments and obtained results will be presented in the report.

Acknowledgment
Present study was supported by the Russian Science Foundation project 19-72-20080
1. Cullen J. et.al. Journal of Magnetism and Magnetic Materials. 2001. V. 226-230. P.948–949.
2. Restorff J. B. et.al. Journal of Applied Physics. 2012. V. 111 (2). P. 023905.
3. Balagurov A. M. et.al. Physical Review Materials. 2024. V. 8. P. 073604.

Speaker: Tatiana Vershinina (JINR)

83 Copper and Nickel Accumulation and Translocation in Leafy Vegetables Irrigated with Metal-Containing Effluents

The treated and untreated wastewaters are widely used for irrigation in many developing countries. They often contain not only organic compounds, but also various metals that are both essential (zinc, copper) and potentially hazardous (chromium, nickel) for human health. Since plants, including leafy vegetables, can accumulate metals both in their roots and edible parts, this can be dangerous when consumed by humans.
The laboratory experiment was performed to assess the accumulation and translocation of copper and nickel in the green and underground parts of lettuce (Lactuca sativa), green onion (Allium fistulosum L.), arugula (Eruca vesicaria) and chard (Beta vulgaris var. cicla) irrigated with metal-containing effluents. The concentration of metals in effluents, soil and vegetables was determined by inductively coupled plasma optical emission spectrometry.
The highest average content of copper in the edible parts of vegetables were determined in lettuce (8.34±2.35 mg/kg) and chard (9.79±1.85 mg/kg). The highest content of nickel was determined in arugula (16.8±3.53 mg/kg) and lettuce (24.1±6.13 mg/kg). The content of copper and nickel in the edible parts of plants irrigated with metal-containing wastewater was 5–15 and 25–91 times, respectively, higher than in the control plants irrigated with filtered water.
The bioaccumulation and translocation factors of copper and nickel for leafy vegetables were calculated to assess their capacity to accumulate metals from the soil and transfer them to the above-ground parts of plants. The values of bioaccumulation factors of copper and nickel varied from 0.6 (onion) to 1.0 (chard) and from 0.3 (arugula) to 1.5 (lettuce), respectively. The leafy vegetables showed a low capacity to transfer copper and nickel from underground to above-ground plant parts. Arugula and lettuce were the exceptions with the values of the translocation factors of 0.7 (nickel) and 0.8 (copper), respectively.
The estimated daily intake (EDI) of nickel and copper was determined based on their content in the edible part of leafy vegetables and their daily consumption. The obtained values were one or two order of magnitude lower than the established reference dose for nickel (0.02 mg/kg bw/day) and the nutritional requirements for copper (2-3 mg/day for adults; 0.5-0.7 mg/day for infants).

Speaker: Aleksandra Kravtsova (JINR)

84 Activation by Neutrons and Related Analytical Methods as a Tool of Medical Elementology

The new direction in medicine that emerged in the second half of the ХХ century –medical elementology – opens fundamental basis for the development and use of new methods of diagnosis and treatment of various diseases, including oncological ones, as well as for solving many other problems facing modern medicine. The subject of research in this new direction consists of four points:
- study of patterns of content and distribution of chemical elements (ChE) in various systems of the human body, organs, tissues, liquids, cells, subcellular structures and biological molecules, under conditions of constant contact and exchange with the environment, considering gender, age, physiological cycles, nationality, race, profession, social status, everyday traditions, lifestyle and bad habits of the individual;
- determination of the role and degree of participation of ChE in the construction and normal functioning of vital systems of the body at all levels of its organization during the periods of origin, formation, maturity and involution, under conditions of constant contact and exchange with the environment;
- study of adaptive shifts in the content of ChE in the body at all levels of its organization with changing conditions in the environment, extreme loads and external influences;
- identification of the role of ChE in the etiology and pathogenesis of various diseases, as well as the effectiveness of using chemical elements in corrective and therapeutic measures.
The outlined subject of the new direction implies a wide range of tasks and their scale. The selected tool - neutron activation analysis (NAA) and related analytical methods, having unique advantages over other methods of determining ChE, allows successfully solving the set tasks.
These unique advantages include the ability to simultaneously determine the content of about 45 ChE in the studied medical and biological samples without their destruction and preliminary preparation for analysis, as well as the ability to in vivo determine some ChE in organs and tissues of the human body. The non-destructibility and multi-element nature of the tool determine its productivity, and in vivo analysis capability is of exceptional interest for the development of non-invasive diagnostic methods.
This report presents specific examples of the use of NAA and related analytical methods in oncology, environmental medicine and pharmaceuticals.

Speaker: Vladimir Zaichick (Medical Radiological Research Center, Obninsk)

85 A Synergy of ICP–MS/AES and Machine Learning for Elemental Characterization of Soil

A comprehensive analysis of soil elemental content in the Nile Delta, Egypt, was conducted using advanced analytical techniques, including Inductively Coupled Plasma Atomic Emission Spectrometry (ICP–AES) and Inductively Coupled Plasma Mass Spectrometry (ICP–MS). A total of 55 elements were analyzed across 53 soil samples. Of these, 10 major elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, and P) were quantified using ICP–AES, while the remaining elements were measured using ICP–MS. The study employed a range of statistical methods, including both descriptive and inferential analyses, to evaluate the data. Additionally, multivariate statistical analysis was applied to gain deeper insights into the shared geochemical characteristics and to identify potential common sources of pollution. Geochemical discriminative ternary diagrams, ratio biplots, and unsupervised machine learning algorithms were utilized to classify the sampling locations based common traits. Various pollution indices were calculated to evaluate the ecological situation in Nile Delta - Egypt. In addition, the background values of the geochemical elements were determined using Bayesian inference, and the influence of outliers was thoroughly analyzed. By integrating the obtained chemical elements through a combination of analytical methods and machine learning algorithms, the background values of elemental content were accurately characterized, providing a precise representation of the soil composition. The collected data can serve as a valuable baseline for monitoring the environmental situation, particularly in terms of elemental abundances, and for assessing future dynamics.

Speaker: Wael Badawy (JINR)

86 Analysis of 234U/238U Ratio by ICP-MS

$ICP-MS$ method has been used for analyses [1] of the elemental and isotope composition (64 elements) of bones of dinosaurs, South mammoths, prehistoric bear and archanthropus as well as the samples of surrounding soils; everything collected in different parts of Uzbekistan. A high concentration of uranium we detected in the bones of dinosaurs (122mg/kg), South mammoth (220mg/kg), prehistoric bear (24mg/kg) and archanthropus (1.5mg/kg) compared to surrounding soils (3.7-7.8 mg/kg) and standard bones (<0.01mg/kg) was established. The standart ratio $^{235}U/^{238}U = 0.007$ was detected for all samples. It was also observed that the $^{234}U/^{238}U$ ratio (Table) differ from $^{234}U/^{238}U = 5.4\times 10^{-5}$ secular equilibrium value. In this report the various mechanisms responsible for this difference are discussed.

Table. Data on uranium isotope ratios, detected by $ICP-MS$ with $1-SD$ errors in prehistoric bones, standard bone, and soils collected around these bones.

Sample $\hspace{0.5cm}$ $^{234}U/^{238}U\times 10^{-5}$ $\hspace{1cm}$ $^{235}U/^{238}U\times 10^{-3}$

MB1 $\hspace{1.4cm}$ 16.0±0.6 $\hspace{3cm}$ 7.4±0.2
SMB1 $\hspace{1.4cm}$ 11±1 $\hspace{3.4cm}$ 7.5±0.2
MB2 $\hspace{1.5cm}$ 9.5±0.2 $\hspace{3.1cm}$ 7.5±0.2
SMB2 $\hspace{1.3cm}$ 8.4±0.4 $\hspace{3.1cm}$ 7.6±0.2
BA $\hspace{1.8cm}$ 8.1±0.2 $\hspace{3cm}$ 7.2±0.2
BB $\hspace{1.8cm}$ 7.7±0.3 $\hspace{3cm}$ 7.4±0.2
DB $\hspace{1.8cm}$ 7.1±0.4 $\hspace{3cm}$ 7.2±0.2
SDB $\hspace{1.6cm}$ 7.2±0.3 $\hspace{3.1cm}$ 7.5±0.2
STB $\hspace{1.6cm}$ 7.2±0.5 $\hspace{3.1cm}$ 7.5±0.2
SSTB $\hspace{1.4cm}$ 10.6±0.3 $\hspace{3cm}$ 7.4±0.2

MB1& & SMB1 – South mammoth bone found in Angren and soil collected near this bone respectively; MB2& SMB2 - South mammoth bone found in Kashkadari and soil collected near this bone respectively; BA-arhantrope bone; BB – bone of bear from Selungur cave; DB& SDB – Dinosaur bone and soil collected near this bone respectively; STB & SSTB – standard bone and soil collected near the standard bone. The natural abundance ratio of the isotopes $^{235}U/^{238}U$ is $0.007257$, secular equilibrium ratio $^{234}U/^{238}U$ is $5.4\times 10^{-5}$ .

[1] I.N. Izosimov, et al., Czech Chemical Society Symposium Series, 20, 116(2022).

Speaker: Igor Izosimov (JINR)

87 A Comprehensive Study of Ruined Mural Fragments from the 12th Century Church of Transfiguration of Our Savior on the Nereditsa Hill (Veliky Novgorog, Russia)

The church of Transfiguration of Our Saviour on the Nereditsa Hill is one of the earliest Old Russian buildings, raised in 1198 by order of Knyaz of Novgorod Yaroslav Vladimirovich. The church was included in the UNESCO list of World Heritage sites in 1992. During the World War II, the monument was partially destroyed. As a result, almost the entire painting crumbled, with the exception of a few fragments. The comprehensive architectural restoration of the church was completed in 2004. Currently, the unique ruined wall paintings need to be studied in more detail in order to carry out work on their restoration. A total of 27 mural fragment were examined in the Sector of Interdisciplinary Research of Cultural Heritage (FLNP JINR, Russia). According to restorers, these fragments date back to the 12th century. Neutron activation analysis with further statistical treatment did not reveal the separation of plaster samples into different groups. A complex of analytical techniques was used to study color layers: X-ray fluorescent analysis, Raman spectroscopy, optical and polarized microscopy. Red and yellow ochre, green earth, lapis lazuli, soot, and lime white were used in the painting of the church. This set is typical for Old Russian painting of that time. Thus, results of comprehensive analysis confirmed that all the samples studied date back to the 12th century.

Speaker: Ekaterina Zhukova (JINR)

13:05 Lunch

Parallel Session 3: Neutron detection & Methodical aspects/Physics of ultracold neutrons: (3)

Convener: Changqing Feng (中国科学技术大学)

88 Energy-Sensitive Photon and Neutron Bimodal Imaging System: Design and Performance Validation

Conventional photon and neutron bimodal imaging systems suffer from inherent limitations such as different imaging beam geometry, leading to challenges in direct fusion of transmission image and system complexity. While the single-source-single-detector configuration based on a compact electron linear accelerator proposed by Tsinghua University addresses imaging beam geometry issue, it remains susceptible to beam-hardening effects that correlate material properties with sample mass-thickness, thereby compromising material identification accuracy. To resolve this problem, this study introduces a quasi-monoenergetic bimodal imaging system utilizing a gamma converter and an event-based detector instead of frame-based detector. The gamma converter ensures monoenergetic photon generation, while Time-of-Flight (TOF) spectrum filtering via the event-based detector achieves quasi-monoenergetic neutron imaging. This paper elaborates on three critical aspects of the system design: energy-sensitive target station optimization, event-based imaging detector configuration, and energy-resolved bimodal reconstruction methods. Experimental results on pure elemental material demonstrate that the proposed system effectively corrects beam-hardening effects, significantly enhancing the reliability of material identification. The performance highlights the system’s potential to establish a robust framework for optimizing the accuracy of bimodal material discrimination.

Speaker: Yuxuan Lai (Tsinghua University)

89 Multi-purpose Time Projection Chamber (MTPC) Signal Simulation Method and Experimental Verification

The Multi-purpose Time Projection Chamber (MTPC) prototype has been successfully developed and commissioned at the CSNS Back-n white neutron beamline. As a novel detection system, its primary design objective focuses on precise measurement of light charged particle emissions in nuclear reactions, while maintaining versatile capabilities for multiple applications including fission cross-section determination, beam profile characterization, and neutron imaging experiments. Our research team has conducted a series of beam tests with the MTPC prototype, obtaining preliminary yet significant experimental results. These initial findings demonstrate the detector's feasibility for conducting neutron-induced nuclear reaction measurements with satisfactory resolution. To support the development of advanced data analysis algorithms, we have established a comprehensive simulation and analysis framework that integrates the operational principles of MTPC with established open-source tools including Geant4 for particle transport simulations, Garfield++ for drift field calculations, and ROOT for data processing. This integrated framework enables parametric studies through systematic variation of experimental conditions, generating simulation predictions that show strong agreement with actual measurement data. The synergy between experimental validation and computational modeling provides valuable insights for detector optimization and experimental design refinement, particularly in understanding complex signal formation processes within the time projection chamber.

Speaker: Haizheng Chen (XJTU)

90 Research and Development of a Large-Size CsI(Tl) Detector for Neutron Capture γ-ray Measurement at the Back-n White Neutron Source of CSNS

Neutron capture reactions play a crucial role in nuclear physics research, as their cross-section measurements provide critical data for nuclear structure studies and nuclear databases, while also enabling the examination of symmetries and conservation laws in nuclear reactions. To meet the requirement for neutron capture cross-section measurements at the back-streaming neutron facility (Back-n) of China Spallation Neutron Source (CSNS), we have developed a large-size CsI(Tl) detector with a diameter of 10 cm and a length of 21 cm. The CsI(Tl) crystal is coupled to a photomultiplier tube (PMT) for signal readout. The PMT's performance, including single-photoelectron response and gain curve were characterized in the laboratory using an LED light source. The reflective layer material, energy response, and uniformity of the CsI(Tl) detector system were evaluated using gamma-ray radioactive sources. Preliminary results demonstrate that the detector achieves a uniformity better than 5% and an energy resolution of 2.5% at 662 keV. Beam experiments for neutron capture cross-section measurements were conducted using lead samples at the Back-n beamline to validate the detector's performance. Based on the preliminary results, an improved experimental protocol has been proposed. This work provides a detailed description of the design of the large-size CsI(Tl) detector system, the results of radioactive source tests, and the progress of beamline experiments.

Speaker: You Lv (CSNS)

91 Test of the Performance of an LGAD-Based Zero-Degree Detector on the CSNS Back-n Beamline

To establish a comprehensive and reliable nuclear database for neutron-induced processes, the development of accelerator-driven system (ADS) technology is essential. Despite many efforts have been made, accurate measurements of light charged ions (LCIs), including protons, tritium, and α particles, at zero degrees in the beam direction remain challenges. Conventional detectors often fail to operate consistently under intense neutron beam fluxes, severely limiting their applications as zero-degree detectors (ZDDs). However, the recent development of low-gain avalanche diode (LGAD) technology, designed to meet the strong demands of the ATLAS experiment during the high-luminosity phase of the Large Hadron Collider (LHC), offers a promising solution. With its ability to withstand 2.5E15 1 MeV neq/cm2 irradiation, 50-µm active thickness, 30-ps timing resolution, cost-effectiveness, and excellent radiation hardness, the LGAD detector emerges as a strong candidate for ZDD applications in neutron-induced process measurements. This report presents a performance evaluation of the LGAD detector as a ZDD on the back-streaming neutron (Back-n) beamline at CSNS. Through cross-section measurements of the 6Li(n, T)α reaction, the LGAD demonstrates excellent performance, showing strong agreement with data from the evaluated nuclear data file (ENDF).

Speaker: Yuhang Guo (CSNS)

ISSIN-31-LGAD-ZDD-guoyh-20250529.pdf

92 Monitoring Neutron Spectrum of Reactor IBR2 Using New Direct Beam Detection System at Small Angle Neutron Scattering Spectrometer (YuMO)

The specific geometry of small angle neutron scattering spectrometer YuMO, a central
hole along the neutron beam direction through the two scattering detectors reaching to direct
beam detector (DBD) located at 35 meters from moderator [1-3]
DBD importance return to determine the transmittance of the sample as a function of
wavelength, due to peculiarities of normalization when the ratio between the scattering values
from the sample and the vanadium standard become close to each other. Additional information
about the procedure can be found in [1,2]. Also to monitor occurring changes at reactor power
on long term.
The new direct beam detector at YuMO is a proportional gas detector with solid state
Boron converter [4-8]. Here we present recording for IBR2 neutron spectrum with different
reactor power by processing empty beam spectrum on DBD, it was shown that the detector
works effectively. Also, comparison between new and old DBD detector showed that both are
stably working. However new DBD have higher efficiency.

Speaker: Ahmed Elmekawy (JINR)

93 Application of Micropattern Detectors from High-Energy Physics for Neutron Detection

The work presents application of the particle detection techniques developed in the field of High-Energy Physics (HEPh) to neutron detection. This area has been growing rapidly over the past decade due to ongoing developments at CERN, JINR and other research centers.

Mictro-Pattern Gaseous Detectors (MPGD), such as GEMs, or Gas Electron Multiplier, Micro-Megas, micro-RWELL, micro-GROOVE, are being produced at CERN and became available for other laboratories. They are used for charged particle detection, operate with the gas gain of about 10,000 and provide good spatial and time resolution. An MPGD detector, which has the entrance window made of a thin neutron-convering foil, turns into a unique detector which is sensitive not only to charged particle, but also to neutrons.

JINR develops the coating technique which allows a thin metalized maylar foil to be covered with a thin layer of B4C. The coating can be done for a large area with extremely high precision. Depending on the application, the thickness of the B4C layer can be between 50 nm and 1 um with a variation of about few nanometers over the whole foil area.

Neutron detection capability of a triple GEM with a B4C-covered entrance window is presented in the talk.

Speaker: Temur Enik (JINR)

Parallel Session 4: Nuclear and related analytical techniques in environmental and materials science: (3)

Convener: Xinxiang Li (University of South China)

94 INAA and XRD Investigation of the Serbian Sector of the Danube River and Its Tributary

To get more data concerning the geochemistry and mineralogy of the Danube River tributaries mainly from the Eastern Serbian sector and to elucidate the status quo of sedimentary material, Instrumental Neutron Activation Analysis (INAA) and X-Ray Diffraction (XRD) were used in tandem to investigate 10 samples of unconsolidated bottom sediments, two samples collected at 1.5 and 7.5 m below the river bed, respectively.
The high sensitivity of INAA coupled with a high accuracy achieved at the IBR-2 reactor, Joint Institute for Nuclear Research (JINR) allowed the determination of the mass fractions with accuracy up to 0.5 mg/kg and lower. In this regard, the mass fraction distribution of 22 elements from Sc (Z= 21) to U (Z=92), including 10 Lanthanides permitted to characterize not only the nature of sedimentary material but also the degree of anthropogenic contamination with seven Presumably Contamination Elements (PCE) V, Cr, Co, Ni, Zn, As, and Sb. The Upper Continental Crust (UCC) was considered as a reference environment for both sediment origin and the contamination degree. The XRD performed at the Geological Institute of Romania (GIR) enabled the determination of the main mineralogical component of the sediments.
Among the investigated trace elements, the incompatible and litophilic elements Sc, Zr, the lanthanides, as well as Hf, Th, and U were used to determine the global nature of sedimentary material. On this matter, more descriptors such as La/Th, Th/U ratios or the Sc-La-Th discriminant ternary diagram pointed towards a remarkable similarity between the depositional material and the UCC, also expressed by the felsic origin as proved by the La/Sc ratio vs. Hf biplot. At their turn, the Th/Sc. vs. Zr/Sc suggested a relatively new, less recirculated material. The similarity to UCC was also documented by the distribution of the lanthanides mass fraction normalized to chondrite, showing the characteristic Eu negative anomaly.
As mentioned before, the mass fractions of the investigated PCE normalized to the corresponding UCC mass fraction, which was considered a pristine, uncontaminated environment, presented increased values of the Contamination Factors (CF) of which values monotonously increased from V of which CF was of 0.91 ± 0.28 to 7.71 ± 4.2 in the case of Sb. As a consequence of this fact, the global Pollution Loading Index (PLI) varied between reached values from 1.24 to 4.04 with an average value of 2.32 ± 0.95, pointing towards a moderate to locally high contamination level.
The XRD results were in good agreement with the INAA ones as the main mineralogical component of sedimentary material consisted mainly of quartz, clay minerals (smectite, illite, and more or less montmorillonite), calcium carbonate, plagioclase feldspars with traces of iron minerals such as magnetite, hematite, and goethite.

Speaker: Octavian G. Duliu (University of Bucharest, Faculty of Physics, Department of Structure of Matter, Earth and Atmospheric Physics, Astrophysics & Geological Institute of Romania)

95 Study of the Wall Painting from the Vladychaya Palata of the Novgorod Kremlin (Velikiy Novgorod, Russia) Using Complementary Physico-Chemical Methods

This work presents the results of a comprehensive study that applied complementary physico-chemical methods to 29 mural fragments from the Vladychnaya Palata in the Novgorod Kremlin. Plaster samples were subjected to neutron activation analysis (NAA) at the WWR-K research reactor (Institute of Nuclear Physics, Kazakhstan) to determine elemental composition. The pigment composition of the paintings was studied using a combination of methods: X-ray fluorescence analysis, micro-Raman spectroscopy, as well as optical and polarized microscopy.
NAA results were statistically treated. K-means clustering revealed two groups of plaster samples. Comparing the statistical treatment results with the pigment composition revealed a richer palette of pigments for one of the sample groups. Visualization of the k-means clustering results with color coding of samples clearly demonstrates the differences between the groups.
Combining results of complementary physico-chemical methods enabled a detailed characterization of the materials used in the wall painting of the Vladychnaya Palata. This data can serve as a basis for further studies in the fields of art history, restoration, and preservation of cultural heritage of Novgorod.

Speaker: Valerii Lobachev (JINR)

96 Radiosensitivity of Rice to Fast Neutrons

Determination of radiosensitivity for plant species is important in order obtain desirable plant characteristics. As a rule, median lethal dose(LD50) is considered as appropriate dose to obtain the highest mutation frequency [1].
Such a task for fast neutrons (FN) is a complex challenge due to the unique properties of neutron radiation, the biological variability of the plant, the difficulty in accurate dosimetry, and the intricate nature of radiation-induced damage. Even for gamma radiation, the LD50 for rice vary widely. For some rice varieties, the LD50 is in the range of 350-390 Gy [2, 3], for different Basmati varieties, the values are lower, about 230 Gy [4], for the Mira-1 variety, 520 Gy [5]. Although many authors consider neutron irradiation as a perspective mutagen for further plant breeding there is still no clear information on the dose-response relationship. Researchers use different fast neutron sources and rice varieties. There is no clear information for the neutrons, while some studies use 10 Gy to produce a new variety, other sources consider 20, 33 Gy as LD30 for FN [6, 7, 8].
As the specific results may vary depending on the experimental conditions, the variety of rice, and the radiation source the aim of our research was to study radiosensitivity of Kazakhstan rice variety “Syr Suluy” on two parameters seedling growth reduction (GR) and median lethal dose (LD50). The seeds were irradiated by fast neutrons at the EG-5 electrostatic generator in the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research (Dubna, Russian Federation). The neutron energy (En) was 4.1 MeV; neutron flux intensity was 3×107 particles/cm2, studied doses were 10, 25, 40, 50, and 75 Gy.
It was found out that the GR50 dose is 40 Gy, while the LD50 is 50 Gy. These data will be used for the further plant mutagenesis studies conducted at the EG-5 and could be extended to other cereals.

Speaker: Yulia Aleksiayenak (JINR)

97 Crystallographic Texture Changes during Martensitic Transformations: X-Ray and Neutron Diffraction Studies and Modeling

Crystallographic texture (or crystallographic preferred orientation) is an inherent property of polycrystalline materials, which defines the anisotropy of their bulk physical properties. Textures are formed during inelastic deformation processes, crystallization, recrystallization, etc. They are also influenced by structural phase transformations, which may be studied in situ. Such experiments are usually performed using diffraction of high-energy synchrotron X-rays, or thermal neutrons.
For diffusionless martensitic transformations, orientation relationships between parent and product phases are often known. It is shown that in this case, bulk crystallographic textures of product phases may be easily modeled from bulk crystallographic textures of parent phases, and variant selection rules may be inferred by comparing model and experimental preferred orientations. When the orientation relationship is not defined, it might be possible to determine it using measured crystallographic textures.
Examples of transformation texture studies will be presented and discussed in detail.

Speaker: Roman Vasin (JINR)

98 Effect of Neutron Irradiation on the Electronic and Optical Properties of AlGaAs/InGaAs-Based Quantum Well Structures

Abstract
The effect of neutron irradiation on the structural, optical, and electronic properties of doped strained heterostructures with AlGaAs/InGaAs/GaAs and AlGaAs/InGaAs/AlGaAs quantum wells was experimentally studied. Heterostructures with a two-dimensional electron gas of different layer constructions were subjected to neutron irradiation in the reactor channel with the fluence range of 2 ·1014 cm−2 ÷ 5·1017 cm−2. The low-temperature photoluminescence spectra, electron concentration and mobility, and high-resolution X-ray diffraction curves were measured after the deactivation and during the neutron irradiation. The work discusses the effect of neutron dose on the conductivity and optical spectra of structures based on InGaAs quantum wells depending on the doping level. The limiting dose of neutron irradiation was also estimated for the successful utilization of AlGaAs/InGaAs/GaAs and AlGaAs/InGaAs/AlGaAs and InAs/Al2O3 heterostructures in electronic applications.

Speaker: Аlmas Yskakov (JINR)

99 Physical Design of a High-Brightness Neutron Source Target Station Using 100 MeV Protons on a Tantalum Target

Physical Design of a High-Brightness Neutron Source Target Station Using 100 MeV Protons on a Tantalum Target

Speaker: Fei Shen (CSNS)

15:35 Coffee Break

Parallel Session 3: Neutron detection & Methodical aspects/Physics of ultracold neutrons: (4)

Convener: Alexander Nezvanov (JINR)

100 Study of SEU Effects and Mitigation Measures for Kintex UltraScale FPGA using CSNS Neutron Beam Lines

The damage effect caused by high energy particles, especially Single Event Upset (SEU), is one of the major factor of failure in SRAM-based FPGA components, for applications in harsh radiation environments, such as space-borne payloads and ground-based large scale particle experiments. With the advancement of the integrated circuit industry, in nowadays the feature size of high-performance FPGAs has entered the scale of nanometers, making SEU effects increasingly severe.
Traditionally, the evaluation of single-event effects (SEE), as well as the verification of mitigation measures, mainly rely on heavy ion beam testing, which has been regarded as the gold standard in the past years. However, the operation of SEE testing using heavy ion beam is relatively complex and expensive. Moreover, the availability of heavy ion beam facilities is limited, conflicting with the rising demand of chip testing and verification.
During the past several years, the presenter’s team has been cooperated tightly with the CSNS Back-n group, to conduct research on radiation-hardening and high-reliability design methodologies for high-performance FPGA devices, using neutron beam lines. We employed neutron time-of-flight (TOF) methodology to characterize the correlation between single-event upset (SEU) cross-section (in BRAM and CRAM) and incident neutron kinetic energy in a Kintex UltraScale FPGA device, which is a representative high performance SRAM-based FPGA with 20 nm CMOS technology. Radiation-hardening measures for SEU mitigation were designed and experimentally validated, as well. The results have been published in the IEEE TNS and JINST journals.
The project will be further extended in future. Our hope is to systematically investigate the energy-dependent correlation between incident neutron kinetic energy and recoil ion's linear energy transfer (LET), both by Monte Carlo simulation for CMOS devices and by carrying out more experiments. We hope providing theoretical foundations for domestic radiation effects evaluation infrastructure development. Our ultimate goal is to establish an effective and systematic methodology for the research and evaluation of SEU in high-performance FPGA devices.

Acknowledgment
This work was supported by the National Key Research and Development Program of China under Grant 2020YFE0202002.

Speaker: Changqing Feng (USTC)

101 A Neutron Detector Designed for ICF Diagnosis

Abstract:
With the advancement of science and technology, the field of Inertial Confinement Fusion (ICF) has entered a new era where fusion yields are sufficiently high to enable nuclear measurements to provide multidimensional information encompassing spatial, temporal, and spectral dimensions. Nevertheless, neutron yield remains one of the most critical parameters of concern in the diagnostics of ICF facilities. Currently, neutron yields must be measured across several orders of magnitude, with the upper limit reaching approximately 2×1016 neutrons per shot.
To address high-intensity ICF neutron yield measurement, a neutron detector based on fission reactions has been developed. Drawing inspiration from the design of Vacuum Compton Diode detectors, this detector comprises a vacuum chamber, front window, collector, anode, and rear window. Its operational principle is as follows: Fusion neutrons pass through the detector's front window and impinge on the collector, which consists of a fission foil with a beryllium substrate (primarily composed of natural uranium). Neutrons interact with uranium to produce fission fragments. As these fragments escape, they ionize the collector material, generating secondary electrons. On average, each fragment produces approximately 300 secondary electrons. The anode, constructed as a stainless-steel grid, is positively biased. The secondary electrons are accelerated by the anode voltage and ejected from the collector, generating a positive signal and recorded by a digital oscilloscope.
This detector exhibits fast temporal response, compact structure, and user-friendly operation, making it suitable for measuring ICF fusion neutron yields. Its measurable range spans from 1×1014 to 1×1018 neutrons per shot.

Key words:
Inertial Confinement Fusion, Fusion Neutron, Neutron Yield, Fission Fragment, Secondary Electron

Speaker: Zhaohui Song (NINT)

102 Novel Neutron Detector Design for Accurate Measurement in Ultra-Iron Nucleosynthesis Study

The current polyethylene-moderated 3He neutron detector suffers from low detection efficiency and a dependence on the neutron energy and emission angle, which hinders the accurate measurement of critical data for astrophysical modeling, such as (α, n), (γ, n) cross sections, and β-delayed neutron emission probabilities. To address this, a novel detector design was proposed, using a large spherical heavy water tank, and a layer of “3He+CF4” gases coupled with surrounding photomultiplier tubes. We used the MCNPX code to calculate detection efficiency dependencies with the neutron energy and emission angle under the different configurations, and obtained an optimal configuration (6 cm thick 11B + 0.2 cm thick Be + 70 cm thick D2O) that can offer a high detection efficiency (76%), a relatively good efficiency flatness (1.02) up to 10 MeV, and a broad scope of emission angle independency with efficiency. Such a leap in fast neutron detector would advance nuclear astrophysics with more accurate measurements.

Speaker: Jianqi Chen (Great Bay University)

103 Laser Plasma Accelerating Ultra-Short Ultra-Intense Electron Beam for Nuclear Applications

With the development of ultra-short and ultra-intense laser technology, laser driven plasma electron acceleration is becoming increasingly mature. Compared with traditional RF acceleration, this acceleration method has significant characteristics - an acceleration gradient three orders of magnitude higher. It is precisely because of its ultra-high acceleration gradient that the accelerated beam has characteristics such as ultra-short <10s fs, dense >1e19 cm-3, and high current >10s kA. This talk will introduce our recent experimental progress in laser accelerated ultra-short and high current electron beams, and introduce their ultra-fast and ultra-intense characteristics into nuclear physics research, exploring their potential applications in ultra-fast and efficient nuclear isomer excitation, ultra-short pulsed neutron source, high energy-resolution neutron resonance absorption spectroscopy.

Speaker: Jie Feng (SJTU)

104 Investigation of the Inverse Leidenfrost Effect in the Production of Moderating Material for Cold Neutron Sources

The dispersed moderating agent for cryogenic moderators of the IBR-2M reactor is produced by the formation of droplets and subsequent freezing in liquid nitrogen. The heat exchange between the droplet and liquid nitrogen leads to intensive local boiling of the liquid nitrogen, resulting in vapor cushioning and heat exchange. This phenomenon is known as the Leidenfrost inverse effect.

The device that utilizes this effect consists of a cryostat and a dropper. The cryostat, a vertical vessel, is filled with liquid nitrogen and is isolated from the bottom and sides of the outer space by a vacuum jacket.Inside the cryostat, cells ensure the freezing of each drop in a separate volume.During the manufacturing process, beads accumulate at the bottom of the cryostat.

The utilization of a "steam cushion" approach enables analytical calculations to determine the duration of ball formation under specific conditions. These conditions include the quasi-static nature of the process, the spherical shape of the drop, and the uniformity of the crystallization process.While this analysis provides a fundamental understanding of the processes involved, it serves as a solid foundation for further research and the practical application of the obtained knowledge.

Speaker: Ivan Litvak (JINR)

105 Installation of New Wide-Aperture Scintillation Detectors ASTRA-M and BSD on the IBR-2M Fourier-Diffractometers: First Results

The Department of Spectrometers Complex (DSC) of IBR-2 plays an important role in maintaining the efficiency and development of the experimental facilities at the IBR-2 reactor. One of the directions of DSC is the development and creation of wide-aperture neutron detectors based on the 6LiF/ZnS(Ag) scintillator. As part of the modernization of the scientific installations of the IBR-2 reactor, the ASTRA-M and BSD detectors were created. At the moment, the detectors have been created and installed on the diffractometers of the IBR-2 reactor.
The report will present the first results obtained from the ASTRA-M and BSD detectors, and provide a comparison with the previous ones.

Speaker: Maxim Podlesnyy (JINR)

106 Development of Polarized 3He at CSNS

The development of polarized neutron technology is pivotal for advancing studies in material science and fundamental physics, particularly in probing magnetic structures and symmetry violations. At the China Spallation Neutron Source (CSNS), significant progress has been made in the design and implementation of polarized 3He neutron spin filters (NSFs) based on spin-exchange optical pumping (SEOP) [1-5]. An off-situ system demonstrated exceptional performance with 77.4% 3He polarization and a polarization lifetime exceeding 200 hours, making it highly suitable for long-duration experiments [2]. The in-situ NSFs also achieve significant progress, building on the first-generation (70 cm × 70 cm × 60 cm, 74.4% ³He polarization) [3], a compact in-situ system (55 cm × 56 cm × 48 cm) was developed [4], integrating a uniform magnetic field (<1.74×10⁻⁴/cm), dual-laser optical pumping, and precise thermal control (±0.15°C) with low-noise NMR monitoring. Validated on the BL-20 beamline, this system achieved 75.66%±0.09% 3He polarization and 96.30% neutron polarization at 2 Å. These advancements have enabled versatile deployment across multiple CSNS beamlines. For instance, the Back-n white neutron source utilizes the in-situ NSF for time-reversal violation studies [5], while a specially designed in-situ NSF for the Very Small Angle Neutron Scattering (VSANS) instrument successfully implemented China’s first polarization-analyzed small-angle neutron scattering (PASANS) technique [6].

As an underdevelopment polarized neutron facility, our group poised to enhance system stability and expand the applications in complex magnetic materials with polarized neutron, such as investigations of magnetic skyrmions and beyond-Standard Model physics. Future efforts will focus on optimizing performance for advanced experiments in nuclear weak interactions and exotic symmetry-breaking phenomena.

[1] Zecong Qin, Chuyi Huang, Z. N. Buck et al., Development of a 3He Gas Filling Station at the China Spallation Neutron Source, CHIN. PHYS. LETT., 38, 5 (2021) 052801.
[2] Chuyi Huang, Junpei Zhang, Fan Ye, et al., Development of a Spin-Exchange Optical Pumping-Based Polarized 3He System at the China Spallation Neutron Source (CSNS), CHIN. PHYS. LETT., 38, 9 (2021) 092801.
[3] Zhang, J., Huang, C., Qin, Z. et al. In-situ optical pumping for polarizing 3He neutron spin filters at the China Spallation Neutron Source. Sci. China Phys. Mech. Astron., 65, 241011 (2022). https://doi.org/10.1007/s11433-021-1876-0.
[4] Jian Tang, Bin Wang, Chuyi Huang et al., A compact in-situ polarized 3He system for neutron scattering[J]. Chin. Phys. Lett., DOI: 10.1088/0256-307X/42/2/022901.
[5] M. Zhang, Z. Yang, J. Zhang et al., First use of a polarized 3He neutron spin filter on the back-n white neutron source of CSNS, Nuclear Inst. and Methods in Physics Research, A (2024), doi: https://doi.org/10.1016/j.nima.2024.170184.
[6] Long Tian, Han Gao, Tianhao Wang et al., Polarization-Analyzed Small-Angle Neutron Scattering with an in-situ 3He neutron spin filter at the China Spallation Neutron Source, arXiv:2501.13647 https://doi.org/10.48550/arXiv.2501.13647.

Acknowledgment
Present study was supported by the GRANT 12425512, U2230107.

Speaker: Junpei Zhang (CSNS)

107 Neutron Displacement ……WITHDRAW

Gallium nitride (GaN) materials have attracted significant attention for neutron detection and related applications due to their exceptional advantages including high-temperature tolerance, high-voltage resistance, rapid response characteristics, etc. The evaluation of irradiation damage and radiation-hardened design for GaN-based devices remains a critical research focus. GaN detector configurations are primarily categorized into two types: multilayer planar structures and AlGaN/GaN heterojunction architectures. This study investigates GaN PIN diodes and AlGaN/GaN high-electron-mobility transistors (HEMTs) fabricated on silicon substrates. Systematic neutron irradiation experiments were conducted to characterize the degradation patterns of electrical performance parameters in these devices post-irradiation. Through TCAD (Technology Computer-Aided Design) simulations, the physical mechanisms underlying irradiation-induced damage were thoroughly analyzed. Furthermore, a comparative assessment of radiation resistance between GaN-based devices and conventional silicon-based counterparts was performed, providing critical insights into the radiation tolerance disparities between these material systems.

Speaker: Yuanyuan Xue (NINT)

Parallel Session 4: Nuclear and related analytical techniques in environmental and materials science: (4)

Convener: Octavian G. Duliu (University of Bucharest, Faculty of Physics, Department of Structure of Matter, Earth and Atmospheric Physics, Astrophysics & Geological Institute of Romania)

108 Experimental Extraction of Neutron Resonance Parameters at 20-300 eV for 147,149Sm

147,149Sm are slow neutron capture (s-process) nuclides in nuclear astrophysics, whose (n,γ) cross-section are the important input parameters in nucleosynthesis net calculation in the Samarium (Sm) region. Additionally, 149Sm is a fission product of 235U with 1% yield, and its neutron resonance parameters play a critical role in reactor neutronics. According to the available nuclear evaluation databases, significant disagreement have been observed in the resonance peaks of 147,149Sm (n,γ) cross section data within the energy range of 20-300 eV. In this study, the neutron capture cross section of the natural Samarium target was measured at the back-streaming white neutron beamline of China Spallation Neutron Source. The neutron capture yield was obtained and the neutron resonance parameters for 147Sm at 107.0，139.4，241.7，and 257.3 eV and 149Sm at 23.2, 24.6, 26.1, 28.0, 51.5, 75.2, 90.9, 125.3, and 248.4 eV were extracted using the SAMMY code based on R-matrix theory. For the parameters Γn and Γγ in these energies of 147,149Sm, the percentages consistent with the results of the CENDL-3.2, ENDF/B-VIII.0, JEFF-3.3, JENDL-4.0, and BROND-3.1 database are 27%, 65%, 65%, 42%, and 58%, respectively. Meanwhile, 27% of the results were inconsistent with them included in any of the major libraries. This work enrichis the experimental data of 147,149Sm neutron capture resonance and helps to clarify the differences between different evaluation databases at the above energies.

Speaker: Xinxiang Li (University of South China)

109 Research on Time-Resolved Prompt Gamma Neutron Activation Analysis Based on Back-n Facility

Time-Resolved Prompt Gamma Neutron Activation Analysis (T-PGAA) is an innovative nuclear analytical technique that combines the advantages of Neutron Resonance Capture Analysis (NRCA) and Prompt Gamma Activation Analysis (PGAA). It exhibits high sensitivity and exceptional isotopic resolution capabilities. T-PGAA holds significant potential in diverse fields such as lunar soil analysis, nuclear leakage tracking, and cultural heritage archaeology. However, the technology remains in its developmental stage, with challenges persisting in data analysis methodologies and system optimization. The Back-n beamline at the China Spallation Neutron Source (CSNS) provides a neutron beam characterized by a broad energy spectrum, high flux intensity, and superior energy resolution, making it an ideal platform for T-PGAA research. In December 2023, an experiment was conducted using a natural lutetium (Lu) target irradiated by neutrons from the Back-n beamline. High-purity germanium detector (HPGe) were employed to measure prompt gamma rays emitted from neutron-induced interactions. By correlating neutron energy derived from time-of-flight (TOF) measurements with characteristic gamma rays and neutron resonance signatures, the isotopic composition and quantitative analysis of the target were achieved. The experimental data underwent systematic processing, including detector calibration, identification of characteristic nuclides, and content analysis. The results confirmed the relative abundance of two isotopes in the Lu target, thereby validating the feasibility of T-PGAA methodology on the Back-n beamline. Additionally, the performance of the detector and data acquisition systems was rigorously tested. This study establishes a foundational framework for analyzing T-PGAA experimental data and paves the way for refining analytical methods.

Speaker: Gaole Yang (SYSU)

110 (Withdrawn)Radiation Effects of White Neutron Source on COTS Devices

The reliability of commercial off-the-shelf (COTS) devices such as solid-state drives (SSDs) under radiation has become a critical concern in space applications and high-altitude environments. Radiation testing has proved to be an effective method for investigating failure mechanisms and evaluating reliability. An overview of the common reliability of SSDs, focusing primarily on failure mechanisms and design mitigation techniques in relation to factors such as NAND program/erase cycles and temperature dependence, is provided in this study.
Commercial solid-state drives (SSDs) were subjected to broad-spectrum neutron exposure at the China Spallation Neutron Source (CSNS) to analyze radiation-induced errors in components and functional interruptions in nonvolatile memory express (NVMe) and serial advanced technology attachment (SATA) SSDs. The experiments revealed apparent sensitivity differences, with NVMe SSDs demonstrating better resistance at the module level due to advanced controller technology and enhanced error correction capabilities than SATA SSDs. For NVMe SSDs, functional interruptions were primarily identified as NAND Flash faults, such as timeouts, and dynamic random access memory (DRAM) errors, such as stuck bits, while controller vulnerabilities contributed minimally. Moreover, this study examines the dominance of read errors as the primary failure mode in NAND Flash and explores how the cumulative characteristic of these errors correlates with functional interruptions.

Acknowledgment
Present study was supported by the Grant U2241280 and Grant Y2022057.

Speaker: Yingqi Ma (NSSC, CAS)

111 Calculation Model and Static Parameters of the IBR-2M Reactor

In this work the results of modeling and simulating the burnup of the IBR-2M pulsed fast reactor in the Monte Carlo software package. A three-dimensional geometric model of the reactor has been developed, including an active zone with 64 fuel assemblies, a PO-3 reactivity modulator, a control and protection system, and a liquid metal sodium coolant. Critical calculations and simulation of the fuel campaign up to an energy production of 2040 MW∙d have been performed, taking into account two fuel refueling.
It was found that the effect of the first replacement of the simulator with a fresh fuel assembly at an energy production of 6 MW∙d∙kg-1 was ~1.55%, and at the next replacement at 18 MW∙d∙kg-1 it was ~1.43% keff. Analysis of the dynamics of the coefficients of non-uniformity of energy release showed an increase in the radial coefficient with a stable axial one, which is associated with the redistribution of the fuel mass after refueling. The critical parameters of the reactor obtained by the Monte Carlo method include keff = 1.0023, the initial reactivity margin of ~2.5 βeff and the neutron generation lifetime of 58 ns.
The results confirm the adequacy of the Monte Carlo model for predicting the behavior of the IBR-2M reactor under fuel burnout conditions and demonstrate the impact of overloads on operational stability and power distribution.

Speaker: Yakov Vdovin (JINR)

112 Mechanical and Temperature Calculations of the Reactivity Modulator Construction of the Research Pulsed Reactor NEPTUN

The NEPTUN reactor is a pulsed periodic research reactor under development with a sodium coolant and a core based on neptunium nitride fuel. The reactor is designed for experiments using extracted beams. Average thermal power is 10-15 MW, pulse half-width is 200 μs, pulse frequency is 10 Hz, time-average thermal neutron flux density is ~1014 cm−2·s−1. The reactor vessel and its core are divided into two parts. A reactivity modulator (RM) is located in the space between parts of the core.
The power pulse (therefore the stability and safety of the reactor) is sensitive to such parameters as the reactivity and the rate of reactivity change. The above parameters depend on the stability of the reactivity modulator. RM is a non-standard design, not used on serial types of reactors. Therefore, there is a need for research of the reactivity modulator construction.
The report presents the results of numerical calculations of a reactivity modulator construction:
• Natural frequencies and oscillation shapes of the reactivity modulator disk. Obtained during modal analysis in the Modal Analysis of the ANSYS software;
• Distribution of stresses, strains and displacements in the RM construction during its rotation. Also, the safety factor of the RM during its rotation is estimated. The results were obtained during mechanical calculations in the Explicit Dynamics module of the ANSYS software;
• Temperature distribution in the RM “window” area at nominal capacity mode of the reactor with forced helium cooling. The results were obtained during thermal calculations in the CFX module of the ANSYS software.

Speaker: Ivan Kushnir (Joint Institute for Nuclear Research)

113 Analysis of Physical Parameters of the New High-Flux Pulse Reactor

The development of a design for a new, high-class reactor, NEPTUNE, is required to effectively continue the neutron research program once the IBR-2M's service life ends and to satisfy new needs. This reactor, like the IBR-2M, will be unique, more powerful, and competitive among other facilities in the world. It will be a tool for physicists, biologists, and creators of new substances and nanomaterials.
To achieve this goal, we plan to increase the flux density of the NEPTUNE by an order of magnitude compared to the IBR-2M. This will allow us to explore completely new objects and conduct a more extensive analysis of research results in real-time. The main goal of our Laboratory is to provide a solid scientific basis for the importance of this new source for scientific research.
In this paper, we will analyze the optimal design of a high-flux, pulsed neutron source and further elaborate on the concept of a pulsed fast reactor. The reactor development involves research on the kinetics and dynamics of power pulses, development of nitride fuel based on 237Np, optimization of main elements' design, and optimization of moderator complex configuration.
One way to optimize physical characteristics is by changing the isotopic composition of fuel to reduce irregularities in fuel rods' energy release, achieving desired average lifetime for neutron generation, and creating conditions for stable reactor operation. To obtain the required neutron spectrum and flux, thermal and cold moderators were optimized. At the same time, it is important to justify the design features of the reactor from the perspective of its safe operation.
This paper outlines the basic design and estimated parameters of a pulsed reactor using 237Np as a nuclear fuel. The main characteristic of the 237Np isotope, compared to traditional nuclear compositions based on 235U and 239Pu, is its threshold nature for fission cross-section (it effectively splits at a neutron energy above 0.4 MeV). This results in the following benefits for the reactor: the lifetime of fast neutron generation in the neptunium zone is approximately 10 nanoseconds, leading to a shorter neutron pulse; the low fraction of delayed neutrons reduces background power between pulses compared to the IBR-2M reactor; there is a little effect on reactivity during fuel burning due to the long half-life of 238Pu; and the efficiency of reactivity modulation can be increased by using materials with good neutron-moderating properties.

Speaker: Dimitar Chereshko (JINR)

114 Neutron Nucleus Parity Violation Experiment on the Back-n Beamline of CSNS

Mofan Zhang1,2
1China Spallation Neutron Source
2Indiana University, zhangmo@iu.edu

Parity Violation (PV) effects in p-wave resonances of compound nucleus has always been the interest of the NOPTREX (Neutron Optical Parity and Time-Reversal EXperiment) collaboration since it may shine lights on the search of Time-Reversal Invariant Violation (TRIV) in the same resonances that exhibit a large PV effect.
NOPTREX collaboration started performing experiments on the Back-n beamline since April of 2023 tested the performance of an in-situ 3He SEOP polarizer to prepare for a future PV experiment on the beamline. (n, γ) angular distribution measurements on 139La and NaI were performed on the GTAF BaF2 array in 2024. The asymmetry in angular distribution of γ-ray from (n, γ) reaction of p-wave resonance relates to the k(J) factor that theoretically correlates the effect of PV and TRIV and could be a method for searching for new p-wave resonances. From the last day of 2024 to early 2025, a measurement on the PV effect of p-wave resonance in 139La was performed. This measurement was the first attempt on PV measurements in China. We did not see the ~10% PV effect of La at 0.74eV p-wave resonance in an un-normalized crude analysis. Further analysis of this first PV experiment data is still ongoing. A second PV experiment with improved setup is preparing and the planned beamtime is late July of 2025.

Speaker: Mofan Zhang (Indiana University / CSNS)

115 Multi-Beam Accelerator-Driven Systems: A Safer and Scalable Approach to Nuclear Waste Transmutation

This study analyzes the differences in the operation and heat distribution of single-beam and multi-beam Accelerator-Driven Systems (ADS) through burn-up simulation calculations. Compared to conventional single-beam configurations, the multi-beam ADS achieves a flat neutron flux and heat distribution, effectively suppressing radial power peaking. The distributed spallation target design in multi-beam ADS enhances minor actinide (MA) incineration efficiency under subcritical conditions while requiring substantially lower proton beam currents to sustain stable operation. These results demonstrate the feasibility of multi-beam architectures as a viable approach to sustainable nuclear waste transmutation, supporting further exploration of next-generation ADS technologies for industrial applications.

Speaker: Xiaochong Zhu (IMP, CAS)

18:10 Dinner

Friday, 30 May

Plenary Session

Convener: Ruirui Fan (高能所)

116 Progress of DBNCT

Speaker: Tianjiao Liang (CSNS)

117 Progress in Advanced Accelerator Driven Nuclear Energy System

Accelerator Driven Subcritical system is believed to be the best candidate for nuclear waste transmutation. In the design scheme of ADS plant with one target, high-intensity external neutrons are concentrated in the center of the core which will result in a high power peak factor. To solve the challenges, a Multi-Beam Accelerator Driven Subcritical（MB-ADS） system is proposed. The spallation target is designed as a unit similar to the fuel assembly. The accelerated beam is split into multi-beams by the radio frequency cavity in the beam line. The spaces between neighbor beams are furtherly enlarged by a duodecuple. The high current proton beam is split into multiple parts and injected into different targets located in the core to improve the beam efficiency and flatten the spatial power distribution of the core. Compared with the results of one target ADS scheme, the reasonable MB-ADS scheme have advantages in both beam efficiency, core power flattening and transmutation.

Speaker: Yuan He (IMP, CAS)

118 Laser-Driven Compact High-Flux Ultrafast Neutron Sources

Neutron sources have been widely applied in numerous fields, ranging from detection technology to medicine and laboratory astrophysics due to their unique features of electrical neutrality and deep penetration capability. Currently, there are two main mechanisms for the generation of neutrons assisted by lasers, i.e., photonuclear reactions (γ, n) and beam-target nuclear reactions. Compared with traditional spallation neutron sources like CSNS, the laser-driven neutron sources have several advantages like high brightness, relatively low cost, compactness, and short duration. Here we show one of the typical laser-driven neutron sources based on ion acceleration via Target Normal Sheath Acceleration with the help of the pitch–catcher model. Cascade simulation results using PIC simulations and Geant4 will be presented and the recent experimental results at SILEX-II and Xingguang will be released. Some potential applications and planned experiments will be discussed.
Acknowledgment
Present study was supported by the NSFC (12375244 and 12135009).

Speaker: Tongpu Yu (NUDT)

10:30 Coffee Break

Plenary Session

Convener: Inga Zinicovscaia (Joint Institute for Nuclear Physics & Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, )

119 Project of High-Brilliance UCN Source at FLNP JINR

The report presents a project of a high brilliance ultracold neutron (UCN) source, which is planned to be constructed at FLNP JINR. It details the concept of the proposed source, the progress made in designing its key components, and the challenges that need to be overcome. A potential research program on this source is also discussed.
As part of this project, it is initially planned to construct a test VCN channel to carry out methodical experiments essential for development of the future source. The report includes the design of this test facility and a brief overview of the research plan for it.

Speaker: German Kulin (JINR)

120 Development of In Situ Sample Environment Technology for Neutron Scattering at CSNS

As one of the important auxiliary devices for neutron scattering instruments, sample environment provides various experimental conditions to enhance the research capabilities of the instruments. The sample environment at the Chinese Spallation Neutron Source (CSNS) has been providing in-situ experimental services since the commissioning of the instrument in 2018. It has evolved from initially serving as a cryostat to now supporting a wide range of sample environments, including low temperature, high temperature, high pressure, and magnetic field, catering to different user needs. The development has enabled the transition from single-sample environment experiments to multiple-sample environment experiments, showcasing the progress from 0 to 1 and from 1 to many in terms of experimental applications. This article primarily introduces the operation and usage of the sample environment at CSNS. It also highlights recent developments and optimizations in sample environment. Additionally, some experimental applications conducted in collaboration with users are also presented.

Acknowledgment
Present study was supported by the National Key R&D Program of China (No. 2024YFE0110004), Youth Innovation Promotion Association CAS, the National Natural Science Foundation of China (No. 12425512), Guangdong Natural Science Funds for Distinguished Young Scholar (No. 2021B1515020101), Guangdong Provincial Key Laboratory of Extreme Conditions (2023B1212010002), China Spallation Neutron Source, etc.

Speaker: Haitao Hu (CSNS)

121 Setting Up High-Energy Polarized Neutron at the China Spallation Neutron Source

Polarized neutrons serve as a critical probe in nuclear physics to investigate spin-dependent interactions and nuclear dynamics. Polarized neutron enables precise studies of nuclear forces, include probing nuclear structure, analyzing reaction mechanisms and resolving nucleon internal spin-quark distributions via deep inelastic scattering. Challenges persist in achieving high polarization stability, measuring low cross-section reactions, advancing our understanding of spin-mediated nuclear phenomena and QCD in dense matter.
We present our recent effort on setting polarized neutron at the China Spallation Neutron Source Back-n beamline, as well as the polarization technique available for future research. Key instrument development in polarized 3He neutron spin filter, guide fields and spin flippers shall be presented, and the corresponding method for designing experiment will be discussed.

Acknowledgment
Present study was supported by the Guangdong Provincial Key Laboratory of Extreme Conditions (2023B1212010002), and the Government-to-Government International Science and Technology Innovation Cooperation Programs (2024YFE0110000)

Speaker: Tianhao Wang (CSNS)

122 Current Status and Experiments of the Back-n White Neutron Facility

The Back-n white neutron facility is a comprehensive experimental platform that serves a wide spectrum of research goals, including nuclear data measurement, experiments in nuclear physics and astrophysics, calibration of neutron detectors, investigation of neutron radiation effects, and applications in archaeology, among others. Operational since 2018, this beamline has facilitated over 300 varied experiments involving international collaborations with China, Russia, and the USA, afford more than 30,000 hours of beam time.

In 2023, the Back-n started employing boron nitride (BN) absorber sheets as a substitute for conventional cadmium sheets, thereby significantly reducing the cutoff energy for low-energy neutrons. This strategic enhancement has broadened the beamline's capacity to include accurate measurement of thermal neutron reaction cross-sections. The substantial neutron flux and extensive beam time have been crucial in securing high-quality statistical data in energy regions that were previously unattainable, leading to notable physical discoveries. These advancements are highlighted by the recently published measurements of the 232Th fission cross-section, which illustrate the improved capabilities of the beamline.

Moreover, Back-n's involvement in the NOPTREX international collaboration has facilitated the conduct of advanced polarized neutron physics experiments, leveraging the SEOP neutron polarization apparatus. The use of polarized neutrons in the eV energy range has enabled a series of fundamental physics experiments, including CP violation experiment etc.

The facility has also experienced significant enhancements in its detection technology. Recent developments include the commissioning of leading-edge detection systems such as a BaF2 detector array (GTAF) for capture cross-section measurements, a Multipurpose Time Projection Chamber (MTPC) for the charged particles and fission cross-sections, and a boron-doped Microchannel Plate detector (BMCP) for total cross-section measurements and neutron resonance radiography. These detectors are among the most advanced neutron detection technologies in the world. Their integration into the Back-n beamline is expected to lead to a wave of pioneering scientific results from the white neutron experiments.

Speaker: Ruirui Fan (CSNS)

Closing

12:30 Lunch