In-situ optical pumping for polarizing 3He neutron spin filters at the China Spallation Neutron Source

In this paper, we present the performance of a recently developed in-situ spin-exchange optically pumped(3) He-neutron spin filter system at the China Spallation Neutron Source (CSNS). The system achieved a He-3 polarization of over 74% at the beamline BL-20. Analysis of neutron transmission experiment results reveals a neutron polarization of > 90% and an average transmission of 27% for 2.2 A neutrons, which were maintained for a duration of 120 h of beam time. To the best of our knowledge, this is the first in-situ hyperpolarized He-3 system incorporated on a neutron beamline in China. This technology is expected to provide stable, wide-angle, and highly polarized neutrons at the CSNS for materials research and fundamental neutron physics.

Automated summary

This paper presents the performance of an in-situ spin-exchange optically pumped He-neutron spin filter system at the China Spallation Neutron Source (CSNS). The system achieved a He-3 polarization of over 74% at the beamline BL-20. Neutron transmission experiment results show a neutron polarization of >90% and an average transmission of 27% for 2.2A neutrons, maintained for 120 hours of beam time. This is the first in-situ hyperpolarized He-3 system incorporated on a neutron beamline in China and is expected to provide stable, wide-angle, and highly polarized neutrons for materials research and fundamental neutron physics at the CSNS.