BICEP3 performance overview and planned Keck Array upgrade

TL;DR

BICEP3 is a high-throughput CMB polarization instrument with a modular design, recently upgraded to 2560 TES detectors, and plans for a multi-frequency BICEP Array to enhance cosmic microwave background observations.

Contribution

This paper reports on BICEP3's performance, its upgrade to 2560 TES detectors, and proposes a new multi-frequency BICEP Array for advanced CMB research.

Findings

BICEP3's optical throughput more than doubles previous instruments.

The upgraded BICEP3 has 2560 TES detectors operational.

Plans for the BICEP Array aim to cover 35-270 GHz with tens of thousands of detectors.

Abstract

BICEP3 is a 520 mm aperture, compact two-lens refractor designed to observe the polarization of the cosmic microwave background (CMB) at 95 GHz. Its focal plane consists of modularized tiles of antenna-coupled transition edge sensors (TESs), similar to those used in BICEP2 and the Keck Array. The increased per-receiver optical throughput compared to BICEP2/Keck Array, due to both its faster f/1.7 optics and the larger aperture, more than doubles the combined mapping speed of the BICEP/Keck program. The BICEP3 receiver was recently upgraded to a full complement of 20 tiles of detectors (2560 TESs) and is now beginning its second year of observation (and first science season) at the South Pole. We report on its current performance and observing plans. Given its high per-receiver throughput while maintaining the advantages of a compact design, BICEP3-class receivers are ideally suited as building blocks for a 3rd-generation CMB experiment, consisting of multiple receivers spanning 35 GHz to 270 GHz with total detector count in the tens of thousands. We present plans for such an array, the new "BICEP Array" that will replace the Keck Array at the South Pole, including design optimization, frequency coverage, and deployment/observing strategies.