Calibration Measurements of the BICEP3 and BICEP Array CMB Polarimeters from 2017 to 2024

• Main Authors: Giannakopoulos, Christos, Vergès, Clara, Ade, P. A. R, Ahmed, Zeeshan, Amiri, Mandana, Barkats, Denis, Thakur, Ritoban Basu, Bischoff, Colin A, Beck, Dominic, Bock, James J, Boenish, Hans, Buza, Victor, CheshireIV, James R, Connors, Jake, Cornelison, James, Crumrine, Michael, Cukierman, Ari Jozef, Denison, Edward, Dierickx, Marion, Duband, Lionel, Eiben, Miranda, Elwood, Brodi D, Fatigoni, Sofia, Filippini, Jeff P, Fortes, Antonio, Gao, Min, Goeckner-Wald, Neil, Goldfinger, David C, Grayson, James A, Grimes, Paul K, Hall, Grantland, Halal, George, Halpern, Mark, Hand, Emma, Harrison, Sam A, Henderson, Shawn, Hubmayr, Johannes, Hui, Howard, Irwin, Kent D, Kang, Jae Hwan, Karkare, Kirit S, Kefeli, Sinan, Kovac, J. M, Kuo, Chao-Lin, Lau, King, Lautzenhiser, Margaret, Lennox, Amber, Liu, Tongtian, Megerian, Koko G, Miller, Oliver, Minutolo, Lorenzo, Moncelsi, Lorenzo, Nakato, Yuka, Nguyen, H. T, O'brient, Roger, Patel, Anika, Petroff, Matthew A, Polish, Anna R, Precup, Nathan, Prouve, Thomas, Pryke, Clement, Reintsema, Carl D, Romand, Thibault, Salatino, Maria, Schillaci, Alessandro, Schmitt, Benjamin, Singari, Baibhav, Soliman, Ahmed, Germaine, Tyler St, Steiger, Aaron, Steinbach, Bryan, Sudiwala, Rashmi, Thompson, Keith L, Tsai, Calvin, Tucker, Carole, Turner, Anthony D, Vieregg, Abigail G, Wandui, Albert, Weber, Alexis C, Willmert, Justin, Wu, Wai Ling K, Yang, Hung-I, Yu, Cyndia, Zeng, Lingzhen, Zhang, Cheng, Zhang, Silvia
• Format: Journal Article
• Language: English
• Published: 24-09-2024
• Subjects: Physics - Cosmology and Nongalactic Astrophysics; Physics - Instrumentation and Methods for Astrophysics
• DOI: 10.48550/arxiv.2409.16440

The BICEP3 and BICEP Array polarimeters are small-aperture refracting
telescopes located at the South Pole designed to measure primordial
gravitational wave signatures in the Cosmic Microwave Background (CMB)
polarization, predicted by inflation. Constraining the inflationary signal
requires not only excellent sensitivity, but also careful control of
instrumental systematics. Both instruments use antenna-coupled orthogonally
polarized detector pairs, and the polarized sky signal is reconstructed by
taking the difference in each detector pair. As a result, the differential
response between detectors within a pair becomes an important systematic effect
we must control. Additionally, mapping the intensity and polarization response
in regions away from the main beam can inform how sidelobe levels affect CMB
measurements. Extensive calibration measurements are taken in situ every
austral summer for control of instrumental systematics and instrument
characterisation. In this work, we detail the set of beam calibration
measurements that we conduct on the BICEP receivers, from deep measurements of
main beam response to polarized beam response and sidelobe mapping. We discuss
the impact of these measurements for instrumental systematics studies and
design choices for future CMB receivers.