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A cryogenic half-wave plate polarimeter using a superconducting magnetic bearing

By Jeff Klein, Asad Aboobaker, Peter A. R. Ade, Francois Aubin, Carlo Baccigalupi, Chaoyun Bao, Julian Borrill, Daniel Chapman, Joy Didier, Matt Dobbs, Benjamin Gold, William F. Grainger, Shaul Hanany, Johannes Hubmayr, Seth Hillbrand, Julien Grain, Andrew Jaffe, Bradley Johnson, Terry Jones, Theodore Kisner, Andrei Korotkov, Sam Leach, Adrian Lee, Lorne Levinson, Michele Limon, Kevin MacDermid, Tomotake Matsumura, Amber Miller, Michael Milligan, Enzo Pascale, Daniel Polsgrove, Nicolas Ponthieu, Kate Raach, Britt Reichborn-Kjennerud, Ilan Sagiv, Radek Stompor, Huan Tran, Matthieu Tristram, Gregory S. Tucker, Amit Yadav, Matias Zaldarriaga and Kyle Zilic

Abstract

We present the design and measured performance of the superconducting magnetic bearing (SMB) that was used successfully as the rotation mechanism in the half-wave plate polarimeter of the E and B Experiment (EBEX) during its North American test flight. EBEX is a NASA-supported balloon-borne experiment that is designed to measure the polarization of the cosmic microwave background. In this implementation the half-wave plate is mounted to the rotor of an SMB that is operating at the sink temperature of 4 K. We demonstrate robust, remote operation on a balloon-borne payload, with angular encoding accuracy of 0.01°. We find rotational speed variation to be 0.2% RMS. We measure vibrational modes and find them to be consistent with a simple SMB model. We search for but do not find magnetic field interference in the detectors and readout. We set an upper limit of 3% of the receiver noise level after 5 minutes of integration on such interference. At 2 Hz rotation we measure a power dissipation of 56 mW. If this power dissipation is reduced, such an SMB implementation is a candidate for low-noise space applications because of the absence of stick-slip friction and low wear

Topics: QB, QC
Publisher: International Society for Optical Engineering
Year: 2011
OAI identifier: oai:http://orca.cf.ac.uk:34561
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