학술논문
Optical characterization of the Keck Array and BICEP3 CMB Polarimeters from 2016 to 2019
Document Type
Working Paper
Author
Collaboration, The BICEP/Keck; Germaine, T. St; Ade, P. A. R.; Ahmed, Z.; Amiri, M.; Barkats, D.; Thakur, R. Basu; Bischoff, C. A.; Bock, J. J.; Boenish, H.; Bullock, E.; Buza, V.; Cheshire, J.; Connors, J.; Cornelison, J.; Crumrine, M.; Cukierman, A.; Dierickx, M.; Duband, L.; Fatigoni, S.; Filippini, J. P.; Fliescher, S.; Grayson, J. A.; Hall, G.; Halpern, M.; Harrison, S.; Hildebrandt, S. R.; Hilton, G. C.; Hui, H.; Irwin, K. D.; Kang, J.; Karkare, K. S.; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Lau, K.; Leitch, E. M.; Megerian, K. G.; Moncelsi, L.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn IV, R. W.; Palladino, S.; Pryke, C.; Racine, B.; Reintsema, C. D.; Richter, S.; Schillaci, A.; Schwarz, R.; Sheehy, C. D.; Soliman, A.; Steinbach, B.; Sudiwala, R. V.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Umilta, C.; Vieregg, A. G.; Wandui, A.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wong, C. L.; Wu, W. L. K.; Yang, E.; Yoon, K. W.; Young, E.; Yu, C.; Zhang, C.
Source
Subject
Language
Abstract
The BICEP/Keck experiment (BK) is a series of small-aperture refracting telescopes observing degree-scale Cosmic Microwave Background (CMB) polarization from the South Pole in search of a primordial $B$-mode signature. This $B$-mode signal arises from primordial gravitational waves interacting with the CMB, and has amplitude parametrized by the tensor-to-scalar ratio $r$. Since 2016, BICEP3 and the Keck Array have been observing with 4800 total antenna-coupled transition-edge sensor detectors, with frequency bands spanning 95, 150, 220, and 270 GHz. Here we present the optical performance of these receivers from 2016 to 2019, including far-field beams measured in situ with an improved chopped thermal source and instrument spectral response measured with a field-deployable Fourier Transform Spectrometer. As a pair differencing experiment, an important systematic that must be controlled is the differential beam response between the co-located, orthogonally polarized detectors. We generate per-detector far-field beam maps and the corresponding differential beam mismatch that is used to estimate the temperature-to-polarization leakage in our CMB maps and to give feedback on detector and optics fabrication. The differential beam parameters presented here were estimated using improved low-level beam map analysis techniques, including efficient removal of non-Gaussian noise as well as improved spatial masking. These techniques help minimize systematic uncertainty in the beam analysis, with the goal of constraining the bias on $r$ induced by temperature-to-polarization leakage to be subdominant to the statistical uncertainty. This is essential as we progress to higher detector counts in the next generation of CMB experiments.
Comment: 8 pages, 3 figures. Accepted by the Journal of Low Temperature Physics (Proceedings of the 18th International Workshop on Low Temperature Detectors)
Comment: 8 pages, 3 figures. Accepted by the Journal of Low Temperature Physics (Proceedings of the 18th International Workshop on Low Temperature Detectors)