Polarization-analyzed small-angle neutron scattering with an in-situ ³He neutron spin filter at the China Spallation Neutron Source

摘要: Polarization-analyzed small-angle neutron scattering (PASANS) is an advanced technique that enables the selective investigation of magnetic scattering phenomena in magnetic materials and distinguishing coherent scattering obscured by an incoherent background, making it particularly valuable for cutting-edge research. The successful implementation of PASANS in China was achieved for the first time at the newly commissioned Very Small Angle Neutron Scattering (VSANS) instrument at the China Spallation Neutron Source (CSNS). This technique employs a combination of a double-V cavity supermirror polarizer and a radio frequency (RF) neutron spin flipper to manipulate the polarization of the incident neutrons. The scattered neutron polarization is stably analyzed by a specially designed in-situ optical pumping ³He neutron spin filter, which covers a spatially symmetric scattering angle coverage of about 4.8^○. A comprehensive PASANS data reduction method, aimed at pulsed neutron beams, has been established and validated with a silver behenate powder sample, achieving a maximum momentum transfer coverage of approximately 0.25 Å^-1.