NIST Develops Neutron Spin Filters for Advanced Research
The National Institute of Standards and Technology (NIST) has developed neutron spin filters (NSFs) using polarized helium-3 gas. These filters offer several advantages over traditional polarizers like supermirrors and Heusler crystals:
1. Broadband capability to polarize cold, thermal, and hot neutrons
2. Ability to polarize large area and divergence neutron beams without increasing divergence
3. Inline add-on device design
4. Efficient polarization flipping by reversing helium-3 nuclear polarization
The adiabatic fast passage nuclear magnetic resonance technique allows integration of polarizer and flipper into a single device. NIST uses polarized helium-3 gas in glass cells to provide polarized beam capability for various instruments at their Center for Neutron Research.
Two optical pumping methods produce the high-density polarized helium-3 gas required: spin-exchange at high pressure (1-10 bar) and metastability-exchange at low pressure (1 mbar) followed by compression. NIST’s NSF program began in 2006 and has been applied to diffuse reflectometry, small-angle neutron scattering, and thermal neutron triple-axis spectrometry. Development is underway for additional instruments at the NCNR.
Source: https://www.nist.gov/ncnr/spin-filters
Keywords: neutron spin filters, Nuclear spin polarized3He gas, polarizer
