A High-Pressure Polarized $^3$He Gas Target for Nuclear Physics Experiments Using A Polarized Photon Beam

TL;DR

This paper reports the development and testing of a high-pressure polarized $^3$He gas target with a novel sol-gel coating, achieving high polarization and reduced background for nuclear physics experiments using polarized photon beams.

Contribution

Introduction of a sol-gel coated high-pressure polarized $^3$He target cell with improved performance and reduced background for nuclear physics experiments.

Findings

Achieved polarization of ~62% in the new target.

The target performance aligns with theoretical predictions.

First use of sol-gel coating in polarized $^3$He targets.

Abstract

Following the first experiment on three-body photodisintegration of polarized $^3$He utilizing circularly polarized photons from High Intensity Gamma Source (HI$\gamma$S) at Duke Free Electron Laser Laboratory (DFELL), a new high-pressure polarized $^3$He target cell made of pyrex glass coated with a thin layer of sol-gel doped with aluminum nitrate nonahydrate has been built in order to reduce the photon beam induced background. The target is based on the technique of spin-exchange optical pumping of hybrid rubidium and potassium and the highest polarization achieved is $\sim$62% determined from both NMR-AFP and EPR polarimetry. The $X$ parameter is estimated to be $\sim0.06$ and the performance of the target is in good agreement with theoretical predictions. We also present beam test results from this new target cell and the comparison with the GE180 $^3$He target cell used previously at HI$\gamma$S. This is the first time that sol-gel coating technique has been used in a polarized $^3$He target for nuclear physics experiments.