We discuss a systematic effect associated with measuring polarization with a continuously rotating half-wave plate. The effect was identified with the data from the E and B Experiment (EBEX), which was a balloon-borne instrument designed to measure the polarization of the CMB as well as that from Galactic dust. The data show polarization fraction larger than 10\% while less than 3\% were expected from instrumental polarization. We give evidence that the excess polarization is due to detector non-linearity in the presence of a continuously rotating HWP. The non-linearity couples intensity signals into polarization. We develop a map-based method to remove the excess polarization. Applying this method for the 150 (250) GHz bands data we find that 81\% (92\%) of the excess polarization was removed. Characterization and mitigation of this effect is important for future experiments aiming to measure the CMB B-modes with a continuously rotating HWP.
@article{arxiv.1711.01314,
title = {Intensity-Coupled-Polarization in Instruments with a Continuously Rotating Half-Wave Plate},
author = {Joy Didier and Amber D. Miller and Derek Araujo and François Aubin and Christopher Geach and Bradley Johnson and Andrei Korotkov and Kate Raach and Benjamin Westbrook and Karl Young and Asad M. Aboobaker and Peter Ade and Carlo Baccigalupi and Chaoyun Bao and Daniel Chapman and Matt Dobbs and Will Grainger and Shaul Hanany and Kyle Helson and Seth Hillbrand and Johannes Hubmayr and Andrew Jaffe and Terry Jones and Jeff Klein and Adrian Lee and Michele Limon and Kevin MacDermid and Michael Milligan and Enzo Pascale and Britt Reichborn-Kjennerud and Ilan Sagiv and Carole Tucker and Gregory S. Tucker and Kyle Zilic},
journal= {arXiv preprint arXiv:1711.01314},
year = {2019}
}
Comments
43 pages, 12 figures, submitted to the Astrophysical Journal