The TolTEC camera: polarimetric commissioning and performance of the continuously rotating half-wave plate

Lee, Dennis, Novak, Giles A., Berthoud, Marc, Bussan, John, Golenia, Robert, Van Camp, Eric, Wilson, Grant W., DeNigris, Nat S., Ma, Zhiyuan, McCrackan, Michael, Souccar, Kamal, Fissel, Laura M., Bij, Akanksha, Thiel, Felix, Aretxaga, Itziar, Ferrusca, Daniel, Mauskopf, Philip D., Lunde, Emily L., Ade, Peter A. R. ORCID: https://orcid.org/0000-0002-5127-0401, Tucker, Carole E. ORCID: https://orcid.org/0000-0002-1851-3918, Pisano, Giampaolo, Cox, Erin G., Sabin, Laurence, Carrasco-Gonzalez, Carlos, Pasetto, Alice, Gómez-Ruiz, Arturo, Hull, Chat, Austermann, Jason E., Beall, James A., Gao, Jiansong, Vissers, Michael R., Zmuidzinas, Jonas and Gao, Jian-Rong 2022. The TolTEC camera: polarimetric commissioning and performance of the continuously rotating half-wave plate. Presented at: SPIE Astronomical Telescopes + Instrumentation 2022, Montreal, Canada, 17-23 July 2022. Proceedings Volume 12190, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI. SPIE, 10.1117/12.2627725

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Abstract

An ambient-temperature Continuously Rotating Half-Wave Plate (CRHWP) modulates the input polarization signal thereby enabling removal of low-frequency (1/f) noise from polarized flux measurements. This 1/f noise arises from atmospheric turbulence as well as from effects intrinsic to certain detectors. Here, we describe the design and performance of the half wave plate rotator and achromatic half-wave plate for the the new imaging polarimeter, TolTEC. These components are mounted in front of the cryostat window and operate at ambient temperature. The Half-Wave Plate Rotator (HWPR) spins the half-wave plate at 2 revolutions per second. The rotation mechanism consists of nine air bearings to provide low-friction motion and a frameless torque motor to directly drive rotation. The orientation of the rotor and half-wave plate are recorded using a high-precision optical encoder. We review the experimental requirements and technical design of the rotator as well as the associated electronics, pneumatics, and software.

Item Type:	Conference or Workshop Item (Paper)
Date Type:	Published Online
Status:	Published
Schools:	Physics and Astronomy
Publisher:	SPIE
Date of First Compliant Deposit:	16 February 2023
Date of Acceptance:	31 August 2022
Last Modified:	17 Feb 2023 10:15
URI:	https://orca.cardiff.ac.uk/id/eprint/157094

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