期刊
REVIEW OF SCIENTIFIC INSTRUMENTS
卷 91, 期 12, 页码 -出版社
AIP Publishing
DOI: 10.1063/5.0029006
关键词
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资金
- U.S. Department of Energy, Office of Science, Office of High Energy Physics [DE-AC02-05CH11231]
- LBNL Directed Research and Development (LDRD) Program
- U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internships (SULI) program
- JSPS Leading Initiative for Excellent Young Researchers (LEADER)
- JSPS KAKENHI [JP16K21744, JP18H05539, JP19H00674]
- World Premier International Research Center Initiative (WPI), MEXT, Japan
- Simons Foundation
- Gordon and Betty Moore Foundation
- Templeton Foundation
- National Science Foundation (NSF) [AST-0618398, AST-1212230]
We present the design and laboratory evaluation of a cryogenic continuously rotating half-wave plate (CHWP) for the POLARBEAR-2b (PB-2b) cosmic microwave background receiver, the second installment of the Simons Array. PB-2b will observe at 5200 m elevation in the Atacama Desert of Chile in two frequency bands centered at 90 GHz and 150 GHz. In order to suppress atmospheric 1/f noise and mitigate systematic effects that arise when differencing orthogonal detectors, PB-2b modulates linear sky polarization using a CHWP rotating at 2 Hz. The CHWP has a 440 mm clear aperture diameter and is cooled to approximate to 50 K in the PB-2b receiver cryostat. It consists of a low-friction superconducting magnetic bearing and a low-torque synchronous electromagnetic motor, which together dissipate < 2 W. During cooldown, a grip-and-release mechanism centers the rotor to < 0.5 mm, and during continuous rotation, an incremental optical encoder measures the rotor angle with a noise level of 0.1 mu rad/root Hz. We discuss the experimental requirements for the PB-2b CHWP, the designs of its various subsystems, and the results of its evaluation in the laboratory. The presented CHWP has been deployed to Chile and is expected to see first light on PB-2b in 2020 or 2021.
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