neutron polarising filters — theoretical comparison with supermirrors and Heusler alloy polarisers

Basic Concepts of Polarisation Analysis for Neutron Chopper Spectrometer POLANO at J-PARC

“…As a practical solution, we plan to approach the target energy range via phased approaches beginning with E i ∼ 25 meV, while simultaneously developing the polarisation devices. 3 He spin filters are most suitable as polarisers for white neutrons. A continuous polarising spin-exchange optical pumping (SEOP) 3 He polariser will be installed in POLANO because it can maintain stable polarisation of the incident neutron beam.…”

“…3 He spin filters are most suitable as polarisers for white neutrons. A continuous polarising spin-exchange optical pumping (SEOP) 3 He polariser will be installed in POLANO because it can maintain stable polarisation of the incident neutron beam. As explained later, the 3 He spin filter can already provide optimised conditions in terms of neutron polarisation and transmission up to 80 meV using the currently developed system.…”

“…A continuous polarising spin-exchange optical pumping (SEOP) 3 He polariser will be installed in POLANO because it can maintain stable polarisation of the incident neutron beam. As explained later, the 3 He spin filter can already provide optimised conditions in terms of neutron polarisation and transmission up to 80 meV using the currently developed system. The SEOP system for POLANO is developed as a collaboration between Japan Atomic Energy Agency (JAEA), KEK, and Tohoku Univ.…”

Long-Lifetime Low-Scatter Neutron Polarization Target

“…In order to compare 3 He spin analyzers with existing supermirror spin analyzers, it is first important to understand that the goal is typically both to determine the angular dependence of the scattering cross section while also determining the spin dependence of the cross section. Cussen et al [22] have shown that a measurement to determine the spin-dependent scattering cross section at narrow angular range will take 2.7 times as longer using an optimized 3 He spin filter with 50% n P = than can be achieved using a supermirror. Now consider the fact that the scattered beam may have an extended angular range, perhaps 360°.…”

Simulations of a convergent bender as neutron polariser for NSE spectrometers

“…For optimisation, we chose I Â P 2 as ''figure of merit'', where I is the intensity of neutrons at the exit of the bender and P is the polarisation of the neutron beam, also at the bender exit. This ''figure of merit'' is based on the optimisation of the flipping ratio, P fon =P foff ; on an instrument, where P fon (P foff ) is the polarisation measured at the detector with the spin flipper on (off) [9,10].…”