The EBEX balloon-borne experiment-optics, receiver, and polarimetry

Aboobaker, Asad M., Ade, Peter ORCID: https://orcid.org/0000-0002-5127-0401, Araujo, Derek, Aubin, François, Baccigalupi, Carlo, Bao, Chaoyun, Chapman, Daniel, Didier, Joy, Dobbs, Matt, Geach, Christopher, Grainger, Will, Hanany, Shaul, Helson, Kyle, Hillbrand, Seth, Hubmayr, Johannes, Jaffe, Andrew, Johnson, Bradley, Jones, Terry, Klein, Jeff, Korotkov, Andrei, Lee, Adrian, Levinson, Lorne, Limon, Michele, MacDermid, Kevin, Matsumura, Tomotake, Miller, Amber D., Milligan, Michael, Raach, Kate, Reichborn-Kjennerud, Britt, Sagiv, Ilan, Savini, Giorgio, Spencer, Locke, Tucker, Carole ORCID: https://orcid.org/0000-0002-1851-3918, Tucker, Gregory S. ORCID: https://orcid.org/0000-0002-1851-3918, Westbrook, Benjamin, Young, Karl and Zilic, Kyle 2018. The EBEX balloon-borne experiment-optics, receiver, and polarimetry. Astrophysical Journal Supplement 239 (1) , p. 7. 10.3847/1538-4365/aae434

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Abstract

The E and B Experiment (EBEX) was a long-duration balloon-borne cosmic microwave background (CMB) polarimeter that flew over Antarctica in 2012. We describe the experiment's optical system, receiver, and polarimetric approach and report on their in-flight performance. EBEX had three frequency bands centered on 150, 250, and 410 GHz. To make efficient use of limited mass and space, we designed a 115 cm2 sr high-throughput optical system that had two ambient temperature mirrors and four antireflection-coated polyethylene lenses per focal plane. All frequency bands shared the same optical train. Polarimetry was achieved with a continuously rotating achromatic half-wave plate (AHWP) that was levitated with a superconducting magnetic bearing (SMB). This is the first use of an SMB in astrophysics. Rotation stability was 0.45% over a period of 10 hr, and angular position accuracy was 0fdg01. The measured modulation efficiency was above 90% for all bands. To our knowledge the 109% fractional bandwidth of the AHWP was the broadest implemented to date. The receiver, composed of one lens and the AHWP at a temperature of 4 K, the polarizing grid and other lenses at 1 K, and the two focal planes at 0.25 K, performed according to specifications, giving focal plane temperature stability with a fluctuation power spectrum that had a 1/f knee at 2 mHz. EBEX was the first balloon-borne instrument to implement technologies characteristic of modern CMB polarimeters, including high-throughput optical systems, and large arrays of transition edge sensor bolometric detectors with multiplexed readouts.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	American Astronomical Society
ISSN:	0067-0049
Date of First Compliant Deposit:	20 December 2018
Date of Acceptance:	22 November 2017
Last Modified:	10 May 2023 19:17
URI:	https://orca.cardiff.ac.uk/id/eprint/117847

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