GroundBIRD: A CMB Polarization Experiment with MKID Arrays
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GroundBIRD: A CMB Polarization Experiment with MKID Arrays K. Lee1 · J. Choi2 · R. T. Génova‑Santos3,4 · M. Hattori5 · M. Hazumi6,7 · S. Honda8 · T. Ikemitsu8 · H. Ishida5,9 · H. Ishitsuka7 · Y. Jo1 · K. Karatsu10 · K. Kiuchi11 · J. Komine8 · R. Koyano12 · H. Kutsuma5,9 · S. Mima9 · M. Minowa11 · J. Moon1 · M. Nagai13 · T. Nagasaki9 · M. Naruse12 · S. Oguri9 · C. Otani9 · M. Peel3,4 · R. Rebolo3,4 · J. A. Rubiño‑Martín3,4 · Y. Sekimoto14 · J. Suzuki8 · T. Taino12 · O. Tajima8 · N. Tomita11 · T. Uchida6,7 · E. Won1 · M. Yoshida6,7 Received: 4 August 2019 / Accepted: 28 July 2020 / Published online: 16 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract GroundBIRD is a ground-based experiment for a precise observation of the cosmic microwave background (CMB) polarizations. To achieve high sensitivity at large angular scales, we adopt three features in this experiment: fast rotation scanning, microwave kinetic inductance detector (MKID), and cold optics. The rotation scanning strategy has the advantage to suppress 1/f noise. It also provides a large sky coverage of 40%, which corresponds to the large angular scales of l ∼ 6 . This allows us to constrain the tensor-to-scalar ratio by using low l B-mode spectrum. The focal plane consists of 7 MKID arrays for two target frequencies, 145 GHz and 220 GHz band. There are 161 pixels in total, of which 138 are for 145 GHz and 23 are for 220 GHz. This array is currently under development, and the prototype will soon be evaluated in telescope. The GroundBIRD telescope will observe the CMB at the Teide observatory. The telescope was moved from Japan to Tenerife and is now under test. We present the status and plan of the GroundBIRD experiment. Keywords Cosmic microwave background · Microwave kinetic inductance detector
1 Introduction The cosmic microwave background (CMB) is an isotropic blackbody radiation with a temperature of 2.7255 K [1]. The CMB has small anisotropies at the 10−5 K level in temperature and sub-μK level in polarization. The CMB anisotropies can be
* K. Lee [email protected] Extended author information available on the last page of the article
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Journal of Low Temperature Physics (2020) 200:384–391
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characterized by the angular power spectra and provides numerous information of the early universe [2]. The E-modes of CMB polarization have been well observed by various experiments [1], and lensing B-modes have been measured by other experiments, POLARBEAR and BICEP2 [3, 4]. The B-modes larger than degree scale, generated by primordial gravitational waves predicted by the inflation model, have not been detected yet [5]. The observation of B-modes from the primordial gravitational waves will reveal information about the very early universe hidden behind the background radiations. GroundBIRD is aiming to measure the B-modes of CMB polarization [6]. Earlier this year, we transported the GroundBIRD telescope from Japan to Instituto de Astrofísica de Canarias (IAC). The telescope was assembled a
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