A Compact in situ Polarized ³He System for Neutron Scattering

This study investigates the performance of a new compact (55 cm×56 cm×48 cm) in situ spin-exchange optical pumping ³He neutron spin filter (NSF) system developed at the China Spallation Neutron Source. The enclosed NSF cell, filled with ³He at 2.53 bar, achieved an initial ³He polarization of approximately 60%. After subsequent improvements in the magnetic field and heating system, this in situ system achieved a ³He polarization of 75.66%±0.09%, resulting in 96.30% neutron polarization at 2 Å. This highly compact in situ system is equipped with self-supportive features, pre-pumping capabilities, polarization maintenance, and a low-noise nuclear magnetic resonance system. These advantages significantly reduce the preparation time and simplify polarized neutron experiments, making it suitable for various neutron beamlines in China, particularly those with a limited sample space. These characteristics establish it as a quasi-standardized system that plays a vital role in polarized neutron experiments, including those involving polarized neutron imaging, neutron reflection, the performance calibration of polarized neutron instruments, and the neutron optics parity and time reversal experiment.