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Published May 1, 2013 | Published
Journal Article Open

The Q/U Imaging ExperimenT Instrument


The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the cosmic microwave background, targeting the imprint of inflationary gravitational waves at large angular scales(~1°). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters that form the focal planes use a compact design based on high electron mobility transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 μKs^(1/2)) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter array has a sensitivity of 87 μKs^(1/2) at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0.01. The two arrays together cover multipoles in the range ℓ ~ 25-975. These are the largest HEMT-based arrays deployed to date. This article describes the design, calibration, performance, and sources of systematic error of the instrument.

Additional Information

© 2013 American Astronomical Society. Received 2012 July 31; accepted 2013 February 8; published 2013 April 9. Support for the QUIET instrument and operation comes through the NSF cooperative agreement AST-0506648. Support was also provided by NSF awards PHY-0855887, PHY-0355328, AST-0448909, AST-1010016, and PHY-0551142; KAKENHI 20244041, 20740158, and 21111002; PRODEX C90284; a KIPAC Enterprise grant; and by the Strategic Alliance for the Implementation of New Technologies (SAINT). This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Some work was performed on the Joint Fermilab-KICP Supercomputing Cluster, supported by grants from Fermilab, the Kavli Institute for Cosmological Physics, and the University of Chicago. Some work was performed on the Titan Cluster, owned and maintained by the University of Oslo and NOTUR (the Norwegian High Performance Computing Consortium), and on the Central Computing System, owned and operated by the Computing Research Center at KEK. Portions of this work were performed at the Jet Propulsion Laboratory (JPL) and California Institute of Technology, operating under a contract with the National Aeronautics and Space Administration. The Q-band modules were developed using funding from the JPL R&TD program. We acknowledge the Northrop Grumman Corporation for collaboration in the development and fabrication of HEMT-based cryogenic temperature-compatible MMICs. C.D. acknowledges an STFC Advanced Fellowship and an ERC IRG grant under FP7. R.B. acknowledges support from CONICYT project Basal PFB-06 and ALMA-Conicyt 31070015. A.D.M. acknowledges a Sloan foundation fellowship. H.K.E. acknowledges an ERC Starting Grant under FP7. PWV measurements were provided by the Atacama Pathfinder Experiment (APEX). We thank CONICYT for granting permission to operate within the Chajnantor Scientific Preserve in Chile, and ALMA for providing site infrastructure support. Field operations were based at the Don Esteban facility run by Astro-Norte. We are particularly indebted to the engineers and technician who maintained and operated the telescope: José Cortés, Cristobal Jara, Freddy Muñoz, and Carlos Verdugo. In addition, we acknowledge the following people for their assistance in the instrument design, construction, commissioning, operation, and in data analysis: Augusto Gutierrez Aitken, Colin Baines, Phil Bannister, Hannah Barker, Matthew R. Becker, Alex Blein, April Campbell, Anushya Chandra, Sea Moon Cho, Joelle Cooperrider, Mike Crofts, Emma Curry, Maire Daly, Fritz Dejongh, Joy Didier, Greg Dooley, Hans Eide, Will Grainger, Jonathon Goh, Peter Hamlington, TakeoHiguchi, Seth Hillbrand, Ben Hooberman, Kathryn D. Huff, Norm Jarosik, Eiichiro Komatsu, Jostein Kristiansen, Donna Kubik, Richard Lai, David Leibovitch, Kelly Lepo, Siqi Li,MarthaMalin,Mark McCulloch, Oliver Montes, David Moore, Ian O'Dwyer, Gustavo Orellana, Stephen Osborne, Stephen Padin, Felipe Pedreros, Ashley Perko, Alan Robinson, Jacklyn Sanders, Dale Sanford, Yunior Savon, Mary Soria, Alex Sugarbaker, David Sutton, Matias Vidal, Liza Volkova, Stephanie Xenos, Octavio Zapata, and Mark Zaskowski.

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