分类： 天文学 >> 天文学 提交时间： 2023-02-19
Grace E. Chesmore
Kathleen Harrington
Carlos E. Sierra
Patricio A. Gallardo
Shreya Sutariya
Tommy Alford
Alexandre E. Adler
Tanay Bhandarkar
Gabriele Coppi
Nadia Dachlythra
Joseph Golec
Jon Gudmundsson
Saianeesh K. Haridas
Bradley R. Johnson
Anna M. Kofman
Jeffrey Iuliano
Jeff McMahon
Michael D. Niemack
John Orlowski-Scherer
Karen Perez Sarmiento
摘要： We present near-field radio holography measurements of the Simons Observatory Large Aperture Telescope Receiver optics. These measurements demonstrate that radio holography of complex millimeter-wave optical systems comprising cryogenic lenses, filters, and feed horns can provide detailed characterization of wave propagation before deployment. We used the measured amplitude and phase, at 4K, of the receiver near-field beam pattern to predict two key performance parameters: 1) the amount of scattered light that will spill past the telescope to 300K and 2) the beam pattern expected from the receiver when fielded on the telescope. These cryogenic measurements informed the removal of a filter, which led to improved optical efficiency and reduced side-lobes at the exit of the receiver. Holography measurements of this system suggest that the spilled power past the telescope mirrors will be less than 1\% and the main beam with its near side-lobes are consistent with the nominal telescope design. This is the first time such parameters have been confirmed in the lab prior to deployment of a new receiver. This approach is broadly applicable to millimeter and sub-millimeter instruments.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yuhan Wang
Tanay Bhandarkar
Steve K. Choi
Kevin T. Crowley
Shannon M. Duff
Daniel Dutcher
John Groh
Kathleen Harrington
Erin Healy
Bradley Johnson
Jack Lashner
Yaqiong Li
Max Silva-Feaver
Rita Sonka
Suzanne T. Staggs
Samantha Walker
Kaiwen Zheng
摘要： The Simons Observatory is a ground-based cosmic microwave background survey experiment that consists of three 0.5 m small-aperture telescopes and one 6 m large-aperture telescope, sited at an elevation of 5200 m in the Atacama Desert in Chile. SO will deploy 60,000 transition-edge sensor (TES) bolometers in 49 separate focal-plane modules across a suite of four telescopes covering 30/40 GHz low frequency (LF), 90/150 GHz mid frequency (MF), and 220/280 GHz ultra-high frequency (UHF). Each MF and UHF focal-plane module packages 1720 optical detectors spreading across 12 detector bias lines that provide voltage biasing to the detectors. During observation, detectors are subject to varying atmospheric emission and hence need to be re-biased accordingly. The re-biasing process includes measuring the detector properties such as the TES resistance and responsivity in a fast manner. Based on the result, detectors within one bias line then are biased with suitable voltage. Here we describe a technique for re-biasing detectors in the modules using the result from bias-step measurement.
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