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.