CLOVER - A new instrument for measuring the B-mode polarization of the CMB

TL;DR

Clover targets a precise measurement of the CMB's B-mode polarization to probe primordial gravitational waves. The instrument comprises three independent telescopes at 90, 150, and 220 GHz, each with four co-pointed optical assemblies and TES detector arrays, using a phase-modulated pseudo-correlation polarimeter to measure $Q$ and $U$ across $20<\ell<1000$. Deployment at Dome C with cross-linked scanning and periodic rotation mitigates systematics, aiming for a lensing-confusion-limited sensitivity near $r\sim0.005$, with a predicted one-sigma constraint of $\delta r = 0.0037$. Foregrounds and lensing are accounted for, and Clover is designed to achieve its goals through a phased, multi-year observing campaign.

Abstract

We describe the design and expected performance of Clover, a new instrument designed to measure the B-mode polarization of the cosmic microwave background. The proposed instrument will comprise three independent telescopes operating at 90, 150 and 220 GHz and is planned to be sited at Dome C, Antarctica. Each telescope will feed a focal plane array of 128 background-limited detectors and will measure polarized signals over angular multipoles 20 < l < 1000. The unique design of the telescope and careful control of systematics should enable the B-mode signature of gravitational waves to be measured to a lensing-confusion-limited tensor-to-scalar ratio r~0.005.

Figures (2)

• Figure 1: Left: Schematic view of a single observing platform with four co-aligned telescopes each feeding an array of 64 feed-horns. Middle: The central cryostat containing four 64-element feed arrays and the sections behind containing the hybrids and phase switches. Note the twisted waveguide sections mating the horn arrays to the detector array (central cube), allowing the same sky pixels to be brought to the same detector. Right: Schematic of the pseudo-correlation receiver for a single feed.
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