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Proceedings Paper

Development of cosmic ray mitigation techniques for the LiteBIRD space mission (Conference Presentation)
Author(s): Shawn M. Beckman; Adrian T. Lee; Masashi Hazumi; Aritoki Suzuki; Yuto Minami; Noah A. Kurinsky; LiteBIRD Collaboration

Paper Abstract

The next generation inflationary satellite probe, LiteBIRD, aims to detect B-mode polarization at degree scales and larger. With 2,622 detectors, LiteBIRD will observe the sky using a reflector Low-Frequency Telescope (LFT) ranging from 40 – 235 GHz, and a refractor High-Frequency Telescope (HFT) ranging from 280 – 402 GHz. This allows for the characterization and subtraction of synchrotron foregrounds at low frequencies and thermal dust foregrounds at high frequencies. The U.S. LiteBIRD team proposes to deliver detector arrays, along with readout electronics, using lenslet-coupled sinuous antenna arrays in the LFT, and orthomode-transducer-coupled corrugated horn arrays in the HFT, both utilizing TES bolometer detectors cooled to 100 mK base temperatures. With insight from the Planck space mission, we know that an important consideration to make for the LiteBIRD experiment is the effect of cosmic ray impacts on low-ell systematics and data selection efficiency. The two primary mechanisms for these effects are events in on the 100 mK stage causing low-frequency variation in focal-plane temperature, and the propagation of ballistic phonons into nearby detectors causing “glitches”, or pulses in bolometer timestreams. LiteBIRD estimates a 5% data loss due to cosmic ray, utilizing straightforward mitigation techniques to increase thermal sinking and heat capacity of the detector wafers. We report on initial characterization and mitigation of ballistic phonon propagation in prototype detector wafers using 5.49 MeV alpha particles from an Americium-241 source. We look to present test results from mitigation techniques including removal of bulk silicon around the bolometer island, adding palladium and other conductors around the bolometer island, removal of the niobium ground plane around the bolometer island, and variations of the preceding methods.

Paper Details

Date Published: 10 July 2018
Proc. SPIE 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, 107081T (10 July 2018); doi: 10.1117/12.2314288
Show Author Affiliations
Shawn M. Beckman, Univ. of California, Berkeley (United States)
Adrian T. Lee, Univ. of California, Berkeley (United States)
Masashi Hazumi, High Energy Accelerator Research Organization (Japan)
Aritoki Suzuki, Univ. of California, Berkeley (United States)
Yuto Minami, The Univ. of Tokyo (Japan)
Noah A. Kurinsky, Stanford Univ. (United States)
LiteBIRD Collaboration, University of California (United States)

Published in SPIE Proceedings Vol. 10708:
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX
Jonas Zmuidzinas; Jian-Rong Gao, Editor(s)

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