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Open Access Publications from the University of California

The POLARBEAR Fourier transform spectrometer calibrator and spectroscopic characterization of the POLARBEAR instrument.

  • Author(s): Matsuda, F
  • Lowry, L
  • Suzuki, A
  • Aguilar Fáundez, M
  • Arnold, K
  • Barron, D
  • Bianchini, F
  • Cheung, K
  • Chinone, Y
  • Elleflot, T
  • Fabbian, G
  • Goeckner-Wald, N
  • Hasegawa, M
  • Kaneko, D
  • Katayama, N
  • Keating, B
  • Lee, AT
  • Navaroli, M
  • Nishino, H
  • Paar, H
  • Puglisi, G
  • Richards, PL
  • Seibert, J
  • Siritanasak, P
  • Tajima, O
  • Takatori, S
  • Tsai, C
  • Westbrook, B
  • et al.

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We describe the Fourier Transform Spectrometer (FTS) used for in-field testing of the POLARBEAR receiver, an experiment located in the Atacama Desert of Chile which measures the cosmic microwave background (CMB) polarization. The POLARBEAR-FTS (PB-FTS) is a Martin-Puplett interferometer designed to couple to the Huan Tran Telescope (HTT) on which the POLARBEAR receiver is installed. The PB-FTS measured the spectral response of the POLARBEAR receiver with signal-to-noise ratio >20 for ∼69% of the focal plane detectors due to three features: a high throughput of 15.1 sr cm2, optimized optical coupling to the POLARBEAR optics using a custom designed output parabolic mirror, and a continuously modulated output polarizer. The PB-FTS parabolic mirror is designed to mimic the shape of the 2.5 m-diameter HTT primary reflector, which allows for optimum optical coupling to the POLARBEAR receiver, reducing aberrations and systematics. One polarizing grid is placed at the output of the PB-FTS and modulated via continuous rotation. This modulation allows for decomposition of the signal into different harmonics that can be used to probe potentially pernicious sources of systematic error in a polarization-sensitive instrument. The high throughput and continuous output polarizer modulation features are unique compared to other FTS calibrators used in the CMB field. In-field characterization of the POLARBEAR receiver was accomplished using the PB-FTS in April 2014. We discuss the design, construction, and operation of the PB-FTS and present the spectral characterization of the POLARBEAR receiver. We introduce future applications for the PB-FTS in the next-generation CMB experiment, the Simons Array.

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