The POLARBEAR-2 and the Simons Array Experiment
A. Suzuki, P. Ade, Y. Akiba, C. Aleman, K. Arnold, C. Baccigalupi, B. Barch, D. Barron, A. Bender, D. Boettger, J. Borrill, S. Chapman, Y. Chinone, A. Cukierman, M. Dobbs, A. Ducout, R. Dunner, T. Elleflot, J. Errard, G. Fabbian, S. Feeney, C. Feng, T. Fujino, G. Fuller, A. Gilbert, N. Goeckner-Wald, J. Groh, T. De Haan, G. Hall, N. Halverson, T. Hamada, M. Hasegawa, K. Hattori, M. Hazumi, C. Hill, W. Holzapfel, Y. Hori, L. Howe, Y. Inoue, F. Irie, G. Jaehnig, A. Jaffe, O. Jeong, N. Katayama, J. Kaufman, K. Kazemzadeh, B. Keating, Z. Kermish, R. Keskitalo, T. Kisner, A. Kusaka, M. Le Jeune, A. Lee, D. Leon, E. Linder, L. Lowry, F. Matsuda, T. Matsumura, N. Miller, K. Mizukami, J. Montgomery, M. Navaroli, H. Nishino, J. Peloton, D. Poletti, G. Rebeiz, C. Raum, C. Reichardt, P. Richards, C. Ross, K. Rotermund, Y. Segawa, B. Sherwin, I. Shirley, P. Siritanasak, N. Stebor, R. Stompor, J. Suzuki, O. Tajima, S. Takada, S. Takakura, S. Takatori, A. Tikhomirov, T. Tomaru, B. Westbrook, N. Whitehorn, T. Yamashita, A. Zahn, O. Zahn
TL;DR
The paper presents Polarbear-2 and the Simons Array as next-generation CMB polarization experiments targeting B-mode signals from both inflationary gravitational waves and gravitational lensing. The approach centers on a large cryogenic focal plane of dichroic TES bolometers at 95 and 150 GHz, read out with 40-channel frequency-domain multiplexed SQUIDs and supported by high-purity alumina optics to maximize throughput. Foreground mitigation is achieved through multi-frequency observations (95, 150, and 220 GHz) and cross-correlation strategies, enabling tighter cosmological constraints on $r$ and the sum of neutrino masses $\sum m_ν$. Projected performance includes a per-band noise-equivalent temperature of $5.8\,\mu{\rm K}_{\mathrm{CMB}}\sqrt{s}$ and, for the Simons Array, $\sigma(r) = 4\times 10^{-3}$ (statistical) or $6\times 10^{-3}$ at $r=0.1$ with foregrounds, along with $\sigma(\sum m_ν)$ around 19 meV (statistical) to 40 meV with foreground cleaning.
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~$μ$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 $σ(r) = 6\times 10^{-3}$ at $r = 0.1$ and $\sum m_ν(σ=1)$ to 40 meV.