Calibration of Transition-edge Sensor (TES) Bolometer Arrays with Application to CLASS

Abstract

The current and future cosmic microwave background (CMB) experiments fielding kilo-pixel arrays of transition-edge sensor (TES) bolometers require accurate and robust gain calibration methods. We simplify and refactor the standard TES model to directly relate the detector responsivity calibration and optical time constant to the measured TES current $I$ and the applied bias current $I_{\mathrm{b}}$. The calibration method developed for the Cosmology Large Angular Scale Surveyor (CLASS) TES bolometer arrays relies on current versus voltage ($I$-$V$) measurements acquired daily prior to CMB observations. By binning Q-band (40GHz) $I$-$V$ measurements by optical loading, we find that the gain calibration median standard error within a bin is 0.3%. We test the accuracy of this "$I$-$V$ bin" detector calibration method by using the Moon as a photometric standard. The ratio of measured Moon amplitudes between detector pairs sharing the same feedhorn indicates a TES calibration error of 0.5%. We also find that for the CLASS Q-band TES array, calibrating the response of individual detectors based solely on the applied TES bias current accurately corrects TES gain variations across time but introduces a bias in the TES calibration from data counts to power units. Since the TES current bias value is set and recorded before every observation, this calibration method can always be applied to raw TES data and is not subject to $I$-$V$ data quality or processing errors.

19 pages, 7 figures, 5 tables. Submitted to ApJS May 2022. Published ApJS Oct 2022

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• SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope
• CLASS: The Cosmology Large Angular Scale Surveyor
• The Cosmology Large Angular Scale Surveyor
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• Twenty years of PWV measurements in the Chajnantor Area
• Precision control of thermal transport in cryogenic single-crystal silicon devices
• Silicon-Based Antenna-Coupled Polarization-Sensitive Millimeter-Wave Bolometer Arrays for Cosmic Microwave Background Instruments
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• On-sky performance of new 90 GHz detectors for the Cosmology Large Angular Scale Surveyor (CLASS)
• Microwave Observations of Venus with CLASS
• High-Efficiency and Low-Noise Detectors for the Upgraded CLASS 90 GHz Focal Plane
• Binary Classification of Light and Dark Time Traces of a Transition Edge Sensor Using Convolutional Neural Networks