Abstract
We report on the development of a polarization-sensitive dichroic (150/220 GHz) detector array for the Cosmology Large Angular Scale Surveyor (CLASS) delivered to the telescope site in June 2019. In concert with existing 40 and 90 GHz telescopes, the 150/220 GHz telescope will make observations of the cosmic microwave background over large angular scales aimed at measuring the primordial B-mode signal, the optical depth to reionization, and other fundamental physics and cosmology. The 150/220 GHz focal plane array consists of three detector modules with 1020 transition edge sensor bolometers in total. Each dual-polarization pixel on the focal plane contains four bolometers to measure the two linear polarization states at 150 and 220 GHz. Light is coupled through a planar orthomode transducer fed by a smooth-walled feedhorn array made from an aluminum–silicon alloy (CE7). In this work, we discuss the design, assembly, and in-laboratory characterization of the 150/220 GHz detector array. The detectors are photon-noise limited, and we estimate the total array noise-equivalent power to be 2.5 and 4 \({\text {aW}}\,\sqrt{{\text {s}}}\) for 150 and 220 GHz arrays, respectively.
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Acknowledgements
We acknowledge the National Science Foundation Division of Astronomical Sciences for their support of CLASS under Grant Nos. 0959349, 1429236, 1636634, and 1654494. CLASS uses detector technology developed under several previous and ongoing NASA grants. Detector development work at JHU was funded by NASA Grant No. NNX14AB76A. We further acknowledge the very generous support of Jim and Heather Murren (JHU A&S ’88), Matthew Polk (JHU A&S Physics BS ’71), David Nicholson, and Michael Bloomberg (JHU Engineering ’64). CLASS is located in the Parque Astronómico de Atacama in northern Chile under the auspices of the Comisión Nacional de Investigación Científica y Tecnológica de Chile (CONICYT).
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Dahal, S., Amiri, M., Appel, J.W. et al. The CLASS 150/220 GHz Polarimeter Array: Design, Assembly, and Characterization. J Low Temp Phys 199, 289–297 (2020). https://doi.org/10.1007/s10909-019-02317-0
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DOI: https://doi.org/10.1007/s10909-019-02317-0