Advanced polarization analysis capability on the very small-angle neutron scattering instrument at the NIST Center for Neutron Research

Abstract

The Very Small Angle Neutron Scattering (VSANS) diffractometer at the National Institute of Standards and Technology has been commissioned and is in the user program. A large available space of nearly 2 m along the beam in the sample area not only enhances the existing SANS polarization analysis capability, but also makes it possible for implementation of other polarization analysis capabilities which would not be easily available on existing SANS instruments, including grazing-incidence small-angle neutron scattering with polarization analysis and spherical neutron polarimetry. We present two polarized setups, one for high magnetic sample fields and the other for low magnetic sample fields, together with a versatile and flexible operational platform for polarized beam experiments. The design of a magnetostatic cavity device that provides better field homogeneity and thus longer 3He polarization relaxation time is discussed. It consists of an end-compensated magnetic shielded solenoid with non-identical holes to accommodate the divergent scattered beam in a constrained distance. Significant improvement in polarized neutronic performance, 3He polarization relaxation time, and an extended momentum transfer range for polarization analysis are presented. Improved neutron polarizing devices, double V-shaped supermirror polarizer, adiabatic radio-frequency spin flipper, and a 3He spin analyzer have yielded an initial instrumental flipping ratio of 100, allowing for higher sensitivity to detection of weak magnetic features in the sample.

Upgrade of the small-angle neutron scattering diffractometer SANS-J at JRR-3

“…During this halted period, high-intensity time-of-flight (TOF) SANS diffractometers, for example, TAIKAN in the Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex (J-PARC) and the Extended Q-range SANS diffractometer EQ-SANS at Oak Ridge National Laboratory (ORNL), were made available to external users (Takata et al, 2015;Zhao et al, 2010;Heller et al, 2018), existing reactor-type SANS instruments were upgraded (Radulescu et al, 2012;Radulescu et al, 2015;Dewhurst et al, 2016;Houston et al, 2018;Wood et al, 2018;Chen et al, 2023;Barker et al, 2022) and new optical devices for SANS were developed (Glinka et al, 2015;Wu et al, 2020;Wu et al, 2019). SANS-J must be competitive to maintain our scientific productivity.…”