Final Report

Gentile, Thomas R.

关键词: neutron;    spin filter;    polarization;    helium-3;   

DOI  :  10.2172/1123378
RP-ID  :  DOE-NIST-SC0002573
PID  :  OSTI ID: 1123378

学科分类：材料科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

We propose to extend the technique of polarized neutron scattering into new domains by continued development and application of polarized 3He spin-filters. These devices are particularly relevant to the Spallation Neutron Source, as the polarizing monochromators historically used at reactor sources will usually not be suitable polarizers, and wide-angle polarization analysis will be essential. With prior support from the Office of Science, we have developed neutron spin-filters based on the large spin dependence of the cross section for neutron capture by 3He, and applied these devices to a small angle neutron scattering spectrometer (SANS), polarized neutron reflectometers, a thermal energy single crystal diffractometer (SCD), and a thermal energy triple-axis instrument. Our developments have been adopted for application on the magnetism reflectometer at the SNS and for the NIST Center for Neutron Research (NCNR) 3He user capability. Results from both these programs are emerging. We have made significant progress in the past grant period on wide-angle polarization analysis. We have also performed several studies relevant to continuous optical pumping, including collaboration on experiments that have revealed neutron beam effects on spin filters that are continuously pumped by spin-exchange optical pumping. We contributed to an experiment on a neutron interferometer, in which the successful results obtained are directly related to both 3He cell technology and high accuracy 3He -based neutron polarimetry. Implementation of wide-angle polarization analysis will continue to be key thrust for our work in this new proposal. We will also focus on continuous optical pumping and the fundamental issues that determine the achievable 3He polarization. This project will be carried out by a collaboration involving scientists at NIST, Indiana University, Hamilton College, and the Univ. of Wisconsin who are experts in 3He polarization techniques, and materials scientists from the NCNR, SNS, and LENS who are neutron scattering experts. We will collaborate with the staff in the new programs at the NCNR and SNS. In addition, we will welcome the opportunity to interact with other laboratories.