Absolute $\rm ^3$He polarimetry for a double-chambered cell using transmission of thermal neutrons

TL;DR

This paper introduces an absolute $^3$He polarimetry technique using thermal neutron transmission in a double-chambered cell, achieving high precision and aiding nuclear force studies.

Contribution

It presents a novel neutron transmission-based $^3$He polarimetry method for double-chambered cells with high accuracy and systematic control.

Findings

Achieved 1.8% statistical error in $^3$He polarization measurement.

Demonstrated the method at the RIKEN neutron source.

Potential for high-precision spin observable data in nuclear physics.

Abstract

We present an absolute $^3$He polarimetry method based on thermal neutron transmission for a double-chambered cell. This method utilizes the fact that a $^3$He nucleus has a large absorption cross section and a spin dependence for thermal neutrons. The cell had a pumping chamber and a target chamber. Polarized $^3$He gas was produced in the pumping chamber by SEOP and then diffused into the target chamber. The $^3$He polarization in the target chamber was determined by comparing the neutron transmissions with the polarized and unpolarized targets. The measurement was performed at the RIKEN Accelerator-Driven Compact Neutron Source. The $^3$He polarization in the target chamber was determined with a statistical error of 1.8% and systematic uncertainty of 0.6%. This method can be used to obtain high-precision data of spin observables in few-nucleon scattering for the investigation of nuclear forces.