We present spin phase continuous modulation (SPCM), a new method for characterization of neutron beam properties. By utilizing spin-precession modulation induced by two oscillating magnetic fields, the method enables precise determination of neutron velocity and monochromaticity. We derive a theoretical formulation of the SPCM signal and experimentally validate it using measurements with a monochromatized neutron beam, obtaining reasonable agreement between experiment and prediction. SPCM enables quantitative determination of neutron beam velocity and monochromaticity.
@article{arxiv.2605.28661,
title = {Spin Phase Continuous Modulation: A Method for the Measurement of Neutron Monochromaticity},
author = {Ryuto Fujitani and Masahiro Hino and Takashi Higuchi},
journal= {arXiv preprint arXiv:2605.28661},
year = {2026}
}