Development and Application of an eV Neutron Polarization for Parity Violation Studies at CSNS Back-n Beamline
Abstract
The dynamic enhancement of symmetry-breaking effects in neutron-nucleus resonances provides a sensitive testing ground for Time-Reversal Invariance Violation (TRIV). Exploiting this mechanism, the Neutron Optics Parity and Time Reversal Experiment (NOPTREX) seeks to elucidate the origin of the universe's baryon asymmetry. Critical to this effort is the precise measurement of Parity Violation (PV) asymmetries, which is essential to calibrate the nuclear parameters required for future TRIV experiments. To facilitate these studies, we developed an eV polarized neutron at the Back-n white neutron beamline of the China Spallation Neutron Source (CSNS). Neutron polarization is generated by an in-situ Spin-Exchange Optical Pumping (SEOP) He filter. Spin manipulation is performed by an adiabatic spin flipper, while spin polarization is preserved over the flight path by a vacuum transport system equipped with a solenoidal guide field. Experiments successfully measured an asymmetry of approximately (stat.) (sys.) % at the 0.747 eV p-wave resonance of La. These results are in agreement with previous results on this resonance and validate the system's capability for PV measurements.
Cite
@article{arxiv.2602.17742,
title = {Development and Application of an eV Neutron Polarization for Parity Violation Studies at CSNS Back-n Beamline},
author = {Xu Qin and Tianhao Wang and Xuanbo Chen and Changdong Deng and Yongce Gong and Zenghang Huang and Wei Jiang and Zhengquan Liu and Guangyuan Luan and Haotian Luo and Qiuyue Luo and Yongjia Lv and You Lv and Nikolaos Vassilopoulos and Xichao Ruan and William Michael Snow and Kang Sun and Sepehr Samiei and Jian Tang and Shilin Wang and Hongyi Wu and Xiaomin Xiong and Xinyu Yuan and Junpei Zhang and Mofan Zhang and Qiwei Zhang and Qingbo Zheng and Ruirui Fan and Xin Tong},
journal= {arXiv preprint arXiv:2602.17742},
year = {2026}
}