Performance of a continuously rotating half-wave plate on the POLARBEAR telescope
Creators: name: Takakura, Satoru
name: Aguilar, Mario
name: Akiba, Yoshiki
name: Arnold, Kam
name: Baccigalupi, Carlo
name: Barron, Darcy
name: Beckman, Shawn
name: Boettger, David
name: Borrill, Julian
name: Chapman, Scott
name: Chinone, Yuji
name: Cukierman, Ari
name: Ducout, Anne
name: Elleflot, Tucker
name: Errard, Josquin
name: Fabbian, Giulio
name: Fujino, Takuro
name: Galitzki, Nicholas
name: Goeckner-Wald, Neil
name: Halverson, Nils W.
name: Hasegawa, Masaya
name: Hattori, Kaori
name: Hazumi, Masashi
name: Hill, Charles
name: Howe, Logan
name: Inoue, Yuki
name: Jaffe, Andrew H.
name: Jeong, Oliver
name: Kaneko, Daisuke
name: Katayama, Nobuhiko
name: Keating, Brian
name: Keskitalo, Reijo
name: Kisner, Theodore
name: Krachmalnicoff, Nicoletta
name: Kusaka, Akito
name: Lee, Adrian T.
name: Leon, David
name: Lowry, Lindsay
name: Matsuda, Frederick
name: Matsumura, Tomotake
name: Navaroli, Martin
name: Nishino, Haruki
name: Paar, Hans
name: Peloton, Julien
name: Poletti, Davide
name: Puglisi, Giuseppe
name: Reichardt, Christian L.
name: Ross, Colin
name: Siritanasak, Praween
name: Suzuki, Aritoki
name: Tajima, Osamu
name: Takatori, Sayuri
name: Teply, Grant
Publisher: name: arXiv
Year: 2017
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: A continuously rotating half-wave plate (CRHWP) is a promising tool to improve the sensitivity to large angular scales in cosmic microwave background (CMB) polarization measurements. With a CRHWP, single detectors can measure three of the Stokes parameters, $I$, $Q$ and $U$, thereby avoiding the set of systematic errors that can be introduced by mismatches in the properties of orthogonal detector pairs. We focus on the implementation of CRHWPs in large aperture telescopes (i.e. the primary mirror is larger than the current maximum half-wave plate diameter of $\sim$0.5 m), where the CRHWP can be placed between the primary mirror and focal plane. In this configuration, one needs to address the intensity to polarization ($I{\rightarrow}P$) leakage of the optics, which becomes a source of 1/f noise and also causes differential gain systematics that arise from CMB temperature fluctuations. In this paper, we present the performance of a CRHWP installed in the POLARBEAR experiment, which employs a Gregorian telescope with a 2.5 m primary illumination pattern. The CRHWP is placed near the prime focus between the primary and secondary mirrors. We find that the $I{\rightarrow}P$ leakage is larger than the expectation from the physical properties of our primary mirror, resulting in a 1/f knee of 100 mHz. The excess leakage could be due to imperfections in the detector system, i.e. detector non-linearity in the responsivity and time-constant. We demonstrate, however, that by subtracting the leakage correlated with the intensity signal, the 1/f noise knee frequency is reduced to 32 mHz ($\ell \sim$39 for our scan strategy), which is very promising to probe the primordial B-mode signal. We also discuss methods for further noise subtraction in future projects where the precise temperature control of instrumental components and the leakage reduction will play a key role.
description: 27 pages, 5 figures, 3 tables, published version in JCAP. Includes some minor corrections