19 July 2016 Large arrays of dual-polarized multichroic TES detectors for CMB measurements with the SPT-3G receiver
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Detectors for cosmic microwave background (CMB) experiments are now essentially background limited, so a straightforward alternative to improve sensitivity is to increase the number of detectors. Large arrays of multichroic pixels constitute an economical approach to increasing the number of detectors within a given focal plane area. Here, we present the fabrication of large arrays of dual-polarized multichroic transition-edge-sensor (TES) bolometers for the South Pole Telescope third-generation CMB receiver (SPT-3G). The complete SPT-3G receiver will have 2690 pixels, each with six detectors, allowing for individual measurement of three spectral bands (centered at 95 GHz, 150 GHz and 220 GHz) in two orthogonal polarizations. In total, the SPT-3G focal plane will have 16140 detectors. Each pixel is comprised of a broad-band sinuous antenna coupled to a niobium microstrip transmission line. In-line filters are used to define the different band-passes before the millimeter-wavelength signal is fed to the respective Ti/Au TES sensors. Detectors are read out using a 64x frequency domain multiplexing (fMux) scheme. The microfabrication of the SPT-3G detector arrays involves a total of 18 processes, including 13 lithography steps. Together with the fabrication process, the effect of processing on the Ti/Au TES’s Tc is discussed. In addition, detectors fabricated with Ti/Au TES films with Tc between 400 mK 560 mK are presented and their thermal characteristics are evaluated. Optical characterization of the arrays is presented as well, indicating that the response of the detectors is in good agreement with the design values for all three spectral bands (95 GHz, 150 GHz, and 220 GHz). The measured optical efficiency of the detectors is between 0.3 and 0.8. Results discussed here are extracted from a batch of research of development wafers used to develop the baseline process for the fabrication of the arrays of detectors to be deployed with the SPT-3G receiver. Results from these research and development wafers have been incorporated into the fabrication process to get the baseline fabrication process presented here. SPT-3G is scheduled to deploy to the South Pole Telescope in late 2016.
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Chrystian M. Posada, Peter A. R. Ade, Adam J. Anderson, Jessica Avva, Zeeshan Ahmed, Kam S. Arnold, Jason Austermann, Amy N. Bender, Bradford A. Benson, Lindsey Bleem, Karen Byrum, John E. Carlstrom, Faustin W. Carter, Clarence Chang, Hsiao-Mei Cho, Ari Cukierman, David A. Czaplewski, Junjia Ding, Ralu N. S. Divan, Tijmen de Haan, Matt Dobbs, Daniel Dutcher, Wenderline Everett, Renae N. Gannon, Robert J. Guyser, Nils W. Halverson, Nicholas L. Harrington, Kaori Hattori, Jason W. Henning, Gene C. Hilton, William L. Holzapfel, Nicholas Huang, Kent D. Irwin, Oliver Jeong, Trupti Khaire, Milo Korman, Donna L. Kubik, Chao-Lin Kuo, Adrian T. Lee, Erik M. Leitch, Sergi Lendinez Escudero, Stephan S. Meyer, Christina S. Miller, Joshua Montgomery, Andrew Nadolski, Tyler J. Natoli, Hogan Nguyen, Valentyn Novosad, Stephen Padin, Zhaodi Pan, John E. Pearson, Alexandra Rahlin, Christian L. Reichardt, John E. Ruhl, Benjamin Saliwanchik, Ian Shirley, James T. Sayre, Jamil A. Shariff, Erik D. Shirokoff, Liliana Stan, Antony A. Stark, Joshua Sobrin, Kyle Story, Aritoki Suzuki, Qing Yang Tang, Ritoban Basu Thakur, Keith L. Thompson, Carole E. Tucker, Keith Vanderlinde, Joaquin D. Vieira, Gensheng Wang, Nathan Whitehorn, Volodymyr Yefremenko, Ki Won Yoon, "Large arrays of dual-polarized multichroic TES detectors for CMB measurements with the SPT-3G receiver ", Proc. SPIE 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, 991417 (19 July 2016); doi: 10.1117/12.2232912; https://doi.org/10.1117/12.2232912

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