A large-diameter cryogenic rotation stage for half-wave plate polarization modulation on the POLARBEAR-2 experiment

Abstract

We describe the design of a cryogenic rotation stage (CRS) for use with the cryogenic half-wave plate (CHWP) polarization modulator on the POLARBEAR-2b and POLARBEAR-2c (PB2b/c) cosmic microwave background (CMB) experiments, the second and third installments of the Simons Array. Rapid modulation of the CMB polarization signal using a CHWP suppresses 1/f contamination due to atmospheric turbulence and allows a single polarimeter to measure both polarization states, mitigating systematic effects that arise when differencing orthogonal detectors. To modulate the full detector array while avoiding excess photon loading due to thermal emission, the CHWP must have a clear-aperture diameter of > 450 mm and be cooled to < 100 K. We have designed a 454-mm-clear-aperture, < 65 K CRS using a superconducting magnetic bearing driven by a synchronous magnetic motor. We present the specifications for the CRS, its interfacing to the PB2b/c receiver cryostat, its performance in a stand-alone test, and plans for future work.

arXiv commentPREPRINT VERSION. Accepted to the Journal of Low Temperature Physics, Article JLTP-D-17-00265R1 See DOI link, supplied by Springer Publishing, for the fully-reviewed published article and citation information

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Cited by in corpus (8)

• The Simons Observatory: Instrument Overview
• Small Aperture Telescopes for the Simons Observatory
• The EBEX Balloon Borne Experiment - Detectors and Readout
• A cryogenic continuously rotating half-wave plate for the POLARBEAR-2b cosmic microwave background receiver
• Overview of the Medium and High Frequency Telescopes of the LiteBIRD satellite mission
• The Simons Observatory: Beam characterization for the Small Aperture Telescopes
• Studies of Systematic Uncertainties for Simons Observatory: Polarization Modulator Related Effects
• Vibration characteristics of a continuously rotating superconducting magnetic bearing and potential influence to TES and SQUID