Aboobaker, AM;
Ade, P;
Araujo, D;
Aubin, F;
Baccigalupi, C;
Bao, C;
Chapman, D;
... Zilic, K; + view all
(2018)
The EBEX Balloon-borne Experiment-Optics, Receiver, and Polarimetry.
The Astrophysical Journal Supplement Series
, 239
(1)
, Article 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 highthroughput 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 0°. 01. 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.
| Type: | Article |
|---|---|
| Title: | The EBEX Balloon-borne Experiment-Optics, Receiver, and Polarimetry |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4365/aae434 |
| Publisher version: | http://doi.org/10.3847/1538-4365/aae434 |
| Language: | English |
| Additional information: | balloons. cosmic background radiation, cosmology: observation, instrumentation: polarimeters, polarization |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10064677 |
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