Speaker
Description
Neutron polariser and analyser based on polarising supermirror technology [1-3] have been enabling the
widespread use of polarised neutrons in the past decades. Polarising supermirror operates on polarised neu-
tron reflectometr yprinciple san di shighl ysensitiv et oinciden tneutro’s wavelength and incident angle.
Modern neutron beamline ofte nuse sneutro noptica lelement ssuc ha s acombinatio no fcurve dan delliptica
neutron guides to get out of the line of sight to the moderator, increase the transport of selected neutrons
and focus the beam onto a sample. A polariser is placed either inline in a section of the neutron guides or
at the guide exit in the experimental enclosure. At those locations, the beam characteristics are complex,
making it necessary to use simulation for the design evaluation of the polariser. At present, the leading sim-
ulation softwar ear eMcSta s[4,5 ]an dVites s[6] .Whil eman ypolarisin gdevice shav ebee nincorporated ,th
complexity of the interaction between neutron and polarising supermirror and the increasing sophistication
of beamline design demand further development of the simulation code to include physical processes that
could previously be omitte d[7] .W erepor ther e adevelopmen tthat ,i nadditio nt opolarisation-dependen
reflectio nan dtransmissio na tth esupermirro rcoating ,als oinclude stransmissio nan dabsorptio ni nsubstrate
refraction at the substrate interface, and multiple internal reflectio ni ndouble-sid ecoate dsupermirror .A tth
device level, multiple reflectio nbetwee nsupermirror sha sals obee ninclude din ,e.g .v-cavit ypolariser .T
results revealed internal reflection si n asubstrat ean dcross-tal kbetwee nsupermirror sca nsignificant lyaff
the performance. Consequently, mitigations have been incorporated in our polariser designs to archive, for
instance, 95% polarisation and 42% transmission at 2 Å for a v-cavity polariser. We will present our finding
and the results of polariser design for ESS instruments using the new code.
[1] P. Böni, Physica B 234-236, 1038 (1997).
[2] T. Krist, C. Lartigue, F. Mezei, Physica B 180-181, 1005 (1992).
[3] T. Bigault, et. al., J. Phys.: Conf. Ser. 528, 012017 (2014).
[4] P. Willendrup and K. Lefmann, J. Neutron Res. 22, 1 (2020).
[5] P. Willendrup and K. Lefmann, J. Neutron Res. 23, 7 (2021).
[6] K. Lieutenant, et. al., Proc. SPIE Int. Soc. Opt. Eng. 5536, 134 (2004).
[7] D. M. Rodríguez, et. al., EPJ Web of Conferences 286, 03008 (2023).
E-mail of the corresponding author: waitung.lee@ess.eu
