Testbed preparation of a small prototype polarization modulator for LiteBIRD Low-Frequency Telescope

Thuong D. Hoang; Tomotake Matsumura; Ryota Takaku; Takashi Hasebe; Tommaso Ghigna; Nobuhiko Katayama; Yuki Sakurai; Kunimoto Komatsu; Teruhito Iida; Yurika Hoshino; Shinya Sugiyama; Hirokazu Ishino

doi:10.1117/12.2630653

31 August 2022 Testbed preparation of a small prototype polarization modulator for LiteBIRD Low-Frequency Telescope

Thuong D. Hoang, Tomotake Matsumura, Ryota Takaku, Takashi Hasebe, Tommaso Ghigna, Nobuhiko Katayama, Yuki Sakurai, Kunimoto Komatsu, Teruhito Iida, Yurika Hoshino, Shinya Sugiyama, Hirokazu Ishino

Author Affiliations +

Proceedings Volume 12190, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI; 121902O (2022) https://doi.org/10.1117/12.2630653
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

LiteBIRD is the Cosmic Microwave Background (CMB) radiation polarization satellite mission led by ISAS/JAXA. The main scientific goal is to search for primordial gravitational wave signals generated from the inflation epoch of the Universe. LiteBIRD telescopes employ polarization modulation units (PMU) using continuously rotating half-wave plates (HWP). The PMU is a crucial component to reach unprecedented sensitivity by mitigating systematic effects, including 1/f noise. We have developed a 1/10 scale prototype PMU of the LiteBIRD LFT, which has a 5-layer achromatic HWP and a diameter of 50 mm, spanning the observational frequency range of 34-161 GHz. The HWP is mounted on a superconducting magnetic bearing (SMB) as a rotor and levitated by a high-temperature superconductor as a stator. In this study, the entire PMU system is cooled down to 10 K in the cryostat chamber by a 4-K Gifford-McMahon (GM) cooler. We propagate an incident coherent millimeter-wave polarized signal throughout the rotating HWP and detect the modulated signal. We study the modulated optical signal and any rotational synchronous signals from the rotation mechanism. We describe the testbed system and the preliminary data acquired from this setup. This testbed is built to integrate the broadband HWP PMU and evaluate the potential systematic effects in the optical data. This way, we can plan with a full-scale model, which takes a long time for preparation and testing.

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Thuong D. Hoang, Tomotake Matsumura, Ryota Takaku, Takashi Hasebe, Tommaso Ghigna, Nobuhiko Katayama, Yuki Sakurai, Kunimoto Komatsu, Teruhito Iida, Yurika Hoshino, Shinya Sugiyama, and Hirokazu Ishino "Testbed preparation of a small prototype polarization modulator for LiteBIRD Low-Frequency Telescope", Proc. SPIE 12190, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI, 121902O (31 August 2022); https://doi.org/10.1117/12.2630653

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