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Published August 2018 | Published + Accepted Version
Journal Article Open

Design and characterization of the Large-aperture Experiment to Detect the Dark Age (LEDA) radiometer systems


The Large-aperture Experiment to Detect the Dark Age (LEDA) was designed to detect the predicted O(100) mK sky-averaged absorption of the cosmic microwave background by hydrogen in the neutral pre- and intergalactic medium just after the cosmological Dark Age. The spectral signature would be associated with emergence of a diffuse Lyα background from starlight during 'Cosmic Dawn'. Recently, Bowman et al. have reported detection of this predicted absorption feature, with an unexpectedly large amplitude of 530 mK, centred at 78 MHz. Verification of this result by an independent experiment, such as LEDA, is pressing. In this paper, we detail design and characterization of the LEDA radiometer systems, and a first-generation pipeline that instantiates a signal path model. Sited at the Owens Valley Radio Observatory Long Wavelength Array, LEDA systems include the station correlator, five well-separated redundant dual polarization radiometers and back-end electronics. The radiometers deliver a 30–85 MHz band (16

Additional Information

© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices). Accepted 2018 May 9. Received 2018 May 8; in original form 2017 September 26. Published: 16 May 2018. This work has benefited from open-source technology shared by the CASPER. We thank the Xilinx University Program for donations; NVIDIA for proprietary tools, discounts, and donations; Digicom for collaboration on manufacture and testing of samplers and ROACH2 processors; and Y. Belopolsky (Bel-Stewart R&D) for collaboration in development of CAT-7A ARJ45 pass-through hardware and cable assemblies. We thank R. Blundell, and P. Riddle of the Smithsonian Astrophysical Observatory Submillimeter Receiver Lab for collaboration on development and fabrication of receivers and other LEDA signal path and control elements. The great dedication, innovation, and exemplary skill of the Caltech Owens Valley Radio Observatory staff, demonstrated in constructing the LWA array, having created a purpose-built facility in no time deserves special mention. LEDA research has been supported in part by NSF grants AST/1106059, PHY/0835713, and OIA/1125087. The OVRO-LWA project was enabled by the kind donation of Deborah Castleman and Harold Rosen. GB acknowledges support from the Royal Society and the Newton Fund under grant NA150184. This work is based on the research supported in part by the National Research Foundation of South Africa under grant 103424. GH acknowledges the support of NSF CAREER award AST/1654815.

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