The EBEX Balloon-borne Experiment—Detectors and Readout
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Author/Creator ORCID
Date
2018-11-06
Type of Work
Department
Program
Citation of Original Publication
Araujo, Derek, et al. The EBEX Balloon-borne Experiment—Detectors and Readout. The Astrophysical Journal Supplement Series 239 (Nov. 6, 2018) 1. https://doi.org/10.3847/1538-4365/aae436.
Rights
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Subjects
Abstract
EBEX was a long-duration balloon-borne experiment to measure the polarization of the cosmic microwave
background. The experiment had three frequency bands centered at 150, 250, and 410 GHz and was the first
to use a kilopixel array of transition edge sensor bolometers aboard a balloon platform. We describe the
design and characterization of the array and the readout system. From the lowest to highest frequency, the
median measured detectors’ average thermal conductances were 39, 53, and 63 pW/K, the medians of
transition temperatures were 0.45, 0.48, and 0.47 K, and the medians of normal resistances were 1.9, 1.5,
and 1.4 Ω; we also give the measured distributions. With the exception of the thermal conductance at 150 GHz,
all measured values are within 30% of their design. We measure median low-loop-gain time constants τ0 = 88,
46, and 57 ms. Two measurements of bolometer absorption efficiency gave results consistent within 10%
and showing high (∼0.9) efficiency at 150 GHz and medium (∼0.35 and ∼0.25) efficiency at the two higher
bands. We measure a median total optical power absorbed of 3.6, 5.3, and 5.0 pW. EBEX pioneered the use
of the digital version of the frequency domain multiplexing system. We multiplexed the bias and readout of
16 bolometers onto two wires. The median per-detector noise-equivalent temperatures are 400, 920, and
14,500 𝜇Kᶜᵐᵇ√s . We compare these values to our preflight predictions and to a previous balloon payload. We
discuss the sources of excess noise and the path for a future payload to make full use of the balloon
environment.