We have developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beam with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to RF neutron spin flippers based on adiabatic fast passage. The spin rotator does not change the kinetic energy of the neutrons and leaves the neutron beam phase space unchanged to high precision. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically-polarized 3He neutron spin filters. The efficiency of the spin rotator was measured to be 98.0+/-0.8% on resonance for neutron energies from 3.3 to 18.4 meV over the full phase space of the beam. As an example of the application of this device to an experiment we describe the integration of the RF spin rotator into an apparatus to search for the small parity-violating asymmetry A_gamma in polarized cold neutron capture on para-hydrogen by the NPDGamma collaboration at LANSCE.
@article{arxiv.0710.2871,
title = {High-Efficiency Resonant RF Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams},
author = {P. -N. Seo and L. Barron-Palos and J. D. Bowman and T. E. Chupp and C. Crawford and M. Dabaghyan and M. Dawkins and S. J. Freedman and T. Gentile and M. T. Gericke and R. C. Gillis and G. L. Greene and F. W. Hersman and G. L. Jones and M. Kandes and S. Lamoreaux and B. Lauss and M. B. Leuschner and R. Mahurin and M. Mason and J. Mei and G. S. Mitchell and H. Nann and S. A. Page and S. I. Penttila and W. D. Ramsay and A. Salas Bacci and S. Santra and M. Sharma and T. B. Smith and W. M. Snow and W. S. Wilburn and H. Zhu},
journal= {arXiv preprint arXiv:0710.2871},
year = {2014}
}