Polarization modulation is a powerful technique to increase the stability of measurements by enabling the distinction of a polarized signal from dominant slow system drifts and unpolarized foregrounds. Furthermore, when placed as close to the sky as possible, modulation can reduce systematic errors from instrument polarization. In this work, we introduce the design and preliminary drive system laboratory performance of a new 60 cm diameter reflective half-wave plate (RHWP) polarization modulator. The wave plate consists of a wire array situated in front of a flat mirror. Using \mbox{50 μm} diameter wires with \mbox{175 μm} spacing, the wave plate will be suitable for operation in the millimeter wavelength range with flatness of the wires and parallelism to the mirror held to a small fraction of a wavelength. The presented design targets the 77--108 GHz range. Modulation is performed by a rotation of the wave plate with a custom rotary drive utilizing an actively controlled servo motor.
@article{arxiv.2208.05005,
title = {Construction of a Large Diameter Reflective Half-Wave Plate Modulator for Millimeter Wave Applications},
author = {Joseph R. Eimer and Michael K. Brewer and David T. Chuss and John Karakla and Rui Shi and John W. Appel and Charles L. Bennett and Joseph Cleary and Sumit Dahal and Rahul Datta and Thomas Essinger-Hileman and Tobias A. Marriage and Carolina Núñez and Matthew A. Petroff and Duncan J. Watts and Edward J. Wollack and Zhilei Xu},
journal= {arXiv preprint arXiv:2208.05005},
year = {2022}
}
Comments
13 pages, 7 figures, to appear in Proc. SPIE Astronomical Telescopes and Instrumentation 2022