Receiver development for BICEP Array, a next-generation CMB polarimeter at the South Pole
Lorenzo Moncelsi, P. A. R. Ade, Zeeshan Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, Colin A. Bischoff, Jamie Bock, Victor Buza, James R. Cheshire, Jake Connors, J. Cornelison, M. Crumrine, A. Cukierman, Edward Denison, M. Dierickx, L. Duband, Miranda Eiben, S. Fatigoni, J. P. Filippini, N. Goeckner-Wald, D. C. Goldfinger, J. Grayson, Paul Grimes, Grantland Hall, Mark Halpern, S. Harrison, Shawn Henderson, S. R. Hildebrandt, Gene Hilton, Johannes Hubmayr, H. Hui, K. D. Irwin, J. Kang, K. S. Karkare, Sinan Kefeli, J. M. Kovac, C. L. Kuo, Kenny Lau, Erik M. Leitch, Krikor G. Megerian, Lorenzo Minutolo, Yuka Nakato, Toshiya Namikawa, Hien T. Nguyen, Roger O’Brient, S. Palladino, Nathan Precup, Thomas Prouvé, C. Pryke, B. Racine, C. D. Reintsema, A. Schillaci, Benjamin L. Schmitt, Ahmed Soliman, T. St. Germaine, B. Steinbach, Rashmi R.Sudiwala astro.cf.ac.uk, Keith L. Thompson, C. Tucker, Anthony D. Turner, Caterina Umiltà, A. G. Vieregg, A. Wandui, Alexis C. Weber, Don Wiebe, J. Willmert, Wai Ling K. Wu, Hung-I E. Yang, Ki Won Yoon, Edward Y. Young, Cyndia Yu, Lingzhen Zeng, Cheng Zhang, Silvia Zhang
Abstract
A detection of curl-type (B-mode) polarization of the primary CMB would be direct evidence for the inflationary paradigm of the origin of the Universe. The Bicep/Keck Array (BK) program targets the degree angular scales, where the power from primordial B-mode polarization is expected to peak, with ever-increasing sensitivity and has published the most stringent constraints on inflation to date. Bicep Array (BA) is the Stage-3 instrument of the BK program and will comprise four Bicep3-class receivers observing at 30/40, 95, 150 and 220/270 GHz with a combined 32,000+ detectors; such wide frequency coverage is necessary for control of the Galactic foregrounds, which also produce degree-scale B-mode signal. The 30/40 GHz receiver is designed to constrain the synchrotron foreground and has begun observing at the South Pole in early 2020. By the end of a 3-year observing campaign, the full Bicep Array instrument is projected to reach σ<sub>r</sub> between 0.002 and 0.004, depending on foreground complexity and degree of removal of B-modes due to gravitational lensing (delensing). This paper presents an overview of the design, measured on-sky performance and calibration of the first BA receiver. We also give a preview of the added complexity in the time-domain multiplexed readout of the 7,776-detector 150 GHz receiver.