Commissioning the CMB polarization telescope GroundBIRD with the full set of detectors

GroundBIRD is a ground-based cosmic microwave background (CMB) experiment for observing the polarization pattern imprinted on large angular scales (ℓ > 6 ) from the Teide Observatory in Tenerife, Spain. Our primary scientific objective is a precise measurement of the optical depth τ (σ(τ ) ∼ 0.01) to the reionization epoch of the Universe to cross-check systematic effects in the measurements made by previous experiments. GroundBIRD observes a wide sky area in the Northern Hemisphere (∼ 40% of the full sky) while continuously rotating the telescope at a high speed of up to 20 rotations per minute (rpm) to overcome the fluctuations of atmospheric radiation. We have adopted the NbTiN/Al hybrid microwave kinetic inductance detectors (MKIDs) as focal plane detectors. We observe two frequency bands centered at 145 GHz and 220 GHz. The 145 GHz band picks up the peak frequency of the CMB spectrum. The 220 GHz band helps accurate removal of the contamination of thermal emission from the Galactic interstellar dust. The MKID arrays (138 MKIDs for 145GHz and 23 MKIDs for 220GHz) were designed and optimized so as to minimize the contamination of the two-level-system noise and maximize the sensitivity. The MKID arrays were successfully installed in May 2023 after the performance verification tests were performed at a laboratory. GroundBIRD has been upgraded to use the full MKID arrays, and scientific observations are now underway. The telescope is automated, so that all observations are performed remotely. Initial validations, including polarization response tests and observations of Jupiter and the moon, have been completed successfully. We are now running scientific observations.

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Published
2024-08-16
DOI
https://doi.org/10.1117/12.3019544
Citations
2
Primary Topic
Superconducting and THz Device Technology
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article
Field-Weighted Citation Impact
0.66
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Commissioning the CMB polarization telescope GroundBIRD with the full set of detectors

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Commissioning the CMB polarization telescope GroundBIRD with the full set of detectors

Hiroki Kutsuma, Yutaro Sekímoto, O. Tajima, Chiko Otani, Yoshinori Sueno, Yonggil Jo, Miku Tsujii, S. Oguri, Yuta Tsuji, J. J. A. Baselmans, S. Honda, Junta Komine, H. Ishitsuka, Taketo Nagasaki, M. Peel, Hoyong Jeong, Makoto Nagai, E. Won, A. Fasano, R. Génova-Santos, K. Karatsu, M. Hazumi, R. Rébolo, David J. Thoen, Keisuke Kataoka, Kenta Kiuchi, Takuji Ikemitsu, Ryo Koyano, Kyungmin Lee, T. Tanaka, J. Suzuki, M. Hattori, Ji‐Hoon Choi, S. Mima, Masato Naruse, Hidesato Ishida, Mitsuhiro Yoshida, J. A. Rubiño-Martín, Nozomu Tomita, Tohru Taino, A. Coppens, Tomohisa Uchida
article en
2 citations

Abstract

GroundBIRD is a ground-based cosmic microwave background (CMB) experiment for observing the polarization pattern imprinted on large angular scales (ℓ > 6 ) from the Teide Observatory in Tenerife, Spain. Our primary scientific objective is a precise measurement of the optical depth τ (σ(τ ) ∼ 0.01) to the reionization epoch of the Universe to cross-check systematic effects in the measurements made by previous experiments. GroundBIRD observes a wide sky area in the Northern Hemisphere (∼ 40% of the full sky) while continuously rotating the telescope at a high speed of up to 20 rotations per minute (rpm) to overcome the fluctuations of atmospheric radiation. We have adopted the NbTiN/Al hybrid microwave kinetic inductance detectors (MKIDs) as focal plane detectors. We observe two frequency bands centered at 145 GHz and 220 GHz. The 145 GHz band picks up the peak frequency of the CMB spectrum. The 220 GHz band helps accurate removal of the contamination of thermal emission from the Galactic interstellar dust. The MKID arrays (138 MKIDs for 145GHz and 23 MKIDs for 220GHz) were designed and optimized so as to minimize the contamination of the two-level-system noise and maximize the sensitivity. The MKID arrays were successfully installed in May 2023 after the performance verification tests were performed at a laboratory. GroundBIRD has been upgraded to use the full MKID arrays, and scientific observations are now underway. The telescope is automated, so that all observations are performed remotely. Initial validations, including polarization response tests and observations of Jupiter and the moon, have been completed successfully. We are now running scientific observations.

High Energy Accelerator Research Organization (JP), University of Tsukuba (JP), The Graduate University for Advanced Studies, SOKENDAI (JP), Tohoku University (JP), Kyoto University (JP), Korea Astronomy and Space Science Institute (KR), Instituto de Astrofísica de Canarias (ES), Space Research Organisation Netherlands (NL)
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