The past, present, and future of the NCNR spin filter program
Wangchun Chen (NIST Center for Neutron research and University of Maryland)
Polarized neutron scattering has been a powerful tool to probe magnetic structures over a variety of length scale, magnetization density and magnetic excitations in a wide range of magnetic materials in physics, chemistry, material science and earth science. Such technique requires apparatus to efficiently polarize neutron beams and to analyze the polarization of the scattered beams. However significant intensity reduction from polarized beam production and analysis and limitations of polarizing monochromators and supermirrors have limited the application of this method. In contrast, neutron spin filters (NSFs) based on polarized 3He gas can effectively polarize a broad wavelength band of neutrons, polarize large area and divergent neutron beams, and decouple polarization selection from energy selection. The 3He neutron spin filter program was initiated at the NCNR in 2006. Over the last decade, polarized neutron measurement capabilities at the NCNR have been significantly advanced using 3He NSFs. I will present developments of polarized neutron instrumentation, including thermal triple axis spectrometry, small-angle neutron scattering, wide-angle polarization analysis, and diffuse reflectometry. I will discuss neutron spin manipulation techniques such as a broadband neutron spin flipper based on inversion of the 3He polarization using the nuclear magnetic resonance technique. These polarized neutron measurement capabilities are opening new scientific opportunities to studies of magnetic nanoparticles assemblies, multiferroics, and superconductivity. The future developments of polarized beam instrumentation will be discussed. Finally, a recent observation of record-high (up to 88%) 3He polarizations achieved by the spin-exchange optical pumping method will be discussed.
Back to Seminar Home Page
Last modified 18-November-2016 by website owner: NCNR (attn: )
