MSE Seminar Series: Wangchun Chen
Friday, February 6, 2015
1:00 p.m.-2:00 p.m.
Room 2110, Chemical and Nuclear Engineering Bldg.
301 405 5240
Polarized Neutron Developments at the NIST Center for Neutron Research
National Institute of Standards and Technology
NIST Center for Neutron Research
Polarized neutron scattering is 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. However polarized neutron scattering is one of the most challenging neutron instrumentation techniques due to significant intensity reduction from polarized beam production and analysis, necessity of precise spin manipulation, and complicated data reduction and analysis. Using a novel neutron polarizing device, nuclear-spin-polarized 3He neutron spin filter (NSF), polarized neutron measurement capabilities have been significantly advanced during the last several years at the NIST Center for Neutron Research (NCNR). I will outline developments of polarized neutron instrumentation using polarized 3He NSFs, including thermal triple axis spectrometry, small-angle neutron scattering, wide-angle polarization analysis, and diffuse reflectometry. These advanced polarized neutron measurement capabilities at the NCNR are opening new scientific opportunities to studies of magnetic nanoparticles assemblies, multiferroics, superconductors, exchange-biased systems, and giant magnetostrictive materials. Examples of such scientific applications will be presented. Finally I will discuss a recent observation of world record high (up to 88%) 3He polarizations achieved by the spin-exchange optical pumping method.
About the Speaker
Wangchun Chen received his Ph.D. in Nuclear Engineering in 2001 from the University of Illinois, Urbana-Champaign. He joined NIST in 2001 as a postdoctoral fellow and later an instrument scientist. He is currently leading polarized neutron development at the National Institute of Standards and Technology Center for Neutron Research. He has developed world-class polarized neutron instrumentation in small neutron scattering, triple-axis spectrometry, and wide-angle polarization analysis. He has co-authored about 50 research publications.