The POLARBEAR-2 and the Simons Array Experiment

TL;DR

The paper describes the design, status, and scientific goals of the POLARBEAR-2 and Simons Array experiments, which aim to measure CMB polarization signals related to gravitational lensing, inflationary gravitational waves, and neutrino masses.

Contribution

It provides a detailed overview of the instrument design, technological innovations, and expected scientific impact of the POLARBEAR-2 and the Simons Array experiments.

Findings

Design of a 7,588 pixel TES bolometer focal plane

Expected noise performance of 5.8 μK_CMB√s per frequency band

Projected constraints on tensor-to-scalar ratio and neutrino mass sum

Abstract

We present an overview of the design and status of the \Pb-2 and the Simons Array experiments. \Pb-2 is a Cosmic Microwave Background polarimetry experiment which aims to characterize the arc-minute angular scale B-mode signal from weak gravitational lensing and search for the degree angular scale B-mode signal from inflationary gravitational waves. The receiver has a 365~mm diameter focal plane cooled to 270~milli-Kelvin. The focal plane is filled with 7,588 dichroic lenslet-antenna coupled polarization sensitive Transition Edge Sensor (TES) bolometric pixels that are sensitive to 95~GHz and 150~GHz bands simultaneously. The TES bolometers are read-out by SQUIDs with 40 channel frequency domain multiplexing. Refractive optical elements are made with high purity alumina to achieve high optical throughput. The receiver is designed to achieve noise equivalent temperature of 5.8~$\mu$K$_{CMB}\sqrt{s}$ in each frequency band. \Pb-2 will deploy in 2016 in the Atacama desert in Chile. The Simons Array is a project to further increase sensitivity by deploying three \Pb-2 type receivers. The Simons Array will cover 95~GHz, 150~GHz and 220~GHz frequency bands for foreground control. The Simons Array will be able to constrain tensor-to-scalar ratio and sum of neutrino masses to $\sigma(r) = 6\times 10^{-3}$ at $r = 0.1$ and $\sum m_\nu (\sigma =1)$ to 40 meV.