Optical Design and Characterization of 40-GHz Detector and Module for the BICEP Array

Abstract

Families of cosmic inflation models predict a primordial gravitational-wave background that imprints B-mode polarization pattern in the Cosmic Microwave Background (CMB). High sensitivity instruments with wide frequency coverage and well-controlled systematic errors are needed to constrain the faint B-mode amplitude. We have developed antenna-coupled Transition Edge Sensor (TES) arrays for high-sensitivity polarized CMB observations over a wide range of millimeter-wave bands. BICEP Array, the latest phase of the BICEP/Keck experiment series, is a multi-receiver experiment designed to search for inflationary B-mode polarization to a precision $\sigma$(r) between 0.002 and 0.004 after 3 full years of observations, depending on foreground complexity and the degree of lensing removal. We describe the electromagnetic design and measured performance of BICEP Array low-frequency 40-GHz detector, their packaging in focal plane modules, and optical characterization including efficiency and beam matching between polarization pairs. We summarize the design and simulated optical performance, including an approach to improve the optical efficiency due to mismatch losses. We report the measured beam maps for a new broad-band corrugation design to minimize beam differential ellipticity between polarization pairs caused by interactions with the module housing frame, which helps minimize polarized beam mismatch that converts CMB temperature to polarization ($T\to P$) anisotropy in CMB maps.

arXiv comment8 pages, 7 figures, Accepted by the Journal of Low Temperature Physics (Proceedings of the 18th International Workshop on Low Temperature Detectors)

References in corpus (6)

• BICEP2 / Keck Array x: Constraints on Primordial Gravitational Waves using Planck, WMAP, and New BICEP2/Keck Observations through the 2015 Season
• BICEP Array: a multi-frequency degree-scale CMB polarimeter
• Antenna-coupled TES bolometers used in BICEP2, Keck array, and SPIDER
• BICEP2/Keck Array IV: Optical Characterization and Performance of the BICEP2 and Keck Array Experiments
• BICEP2 / Keck Array XI: Beam Characterization and Temperature-to-Polarization Leakage in the BK15 Dataset
• Design and performance of wide-band corrugated walls for the BICEP Array detector modules at 30/40 GHz

Cited by in corpus (4)

• Design and performance of the first BICEP Array receiver
• Characterizing the Sensitivity of 40 GHz TES Bolometers for BICEP Array
• Design and Performance of 30/40 GHz Diplexed Focal Plane for BICEP Array
• Receiver development for BICEP Array, a next-generation CMB polarimeter at the South Pole