Speakers
Description
Nuclear reactor safeguard, based on detection of electron antineutrino flux and energy
spectrum, is of great interests to both administrative agencies such as International Atomic Energy
Agency (IAEA) and neutrino community. A dominant reaction channel of such detection is inverse
beta decay (IBD), for which discrimination of gamma against neutron is critical. In this study, pulse
shape discrimination (PSD) is used over plastic scintillator, for its ease of detector assembly, no risk
of leakage, and high chemical stability. Using 22Na and 137Cs radioactive sources to calibrate the
energy response of the whole system (data acquisition and materials), EJ200 and EJ426 scintillator
combination is used as the discrimination setup. The figure of merit (FOM) can reach 9.13 ± 0.01,
and could be adopted to build a reactor neutrino safeguard detector. In addition, the PSD of two
kinds of plastic scintillators were compared. The FOM of the EJ276 plastic scintillator can reach
1.35 ± 0.01 at the energy threshold of 1 MeV gamma equivalent in comparison to 0.96 ± 0.01 of
UPS-113NG at the same energy threshold.
Summary
In this study, a detector system composed of EJ200 and EJ426 plastic scintillators coupled with
an XP3232 PMT was tested for thermal neutron and gamma discrimination. Gamma sources were
used to perform energy calibration by fitting the Compton edges. The FOM value was calculated to be 6.61 ± 0.01 in the whole range of channels. Compared with the EJ276 or UPS-113NG plastic
scintillator systems with fast neutron and gamma discriminating capability, the former has better
discrimination power. Under the threshold of 1 MeV, the FOM of the EJ276 was 1.35 ± 0.01, and
the UPS-113NG was 0.96 ± 0.01. Although the PSD power of EJ276 and UPS-113NG scintillator
systems are weaker than that of EJ200 and EJ426 coupled, they have the advantage of compactness
and less light loss. Therefore, all of them could be viable candidates for small safeguard detectors.
