Paper
26 August 2022 Antenna characterization for the HIRAX experiment
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Abstract
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) aims to improve constraints on the dark energy equation of state through measurements of large-scale structure at high redshift (0.8 < z < 2.5), while serving as a state-of-the-art fast radio burst detector. Bright galactic foregrounds contaminate the 400–800 MHz HIRAX frequency band, so meeting the science goals will require precise instrument characterization. In this paper we describe characterization of the HIRAX antenna, focusing on measurements of the antenna beam and antenna noise temperature. Beam measurements of the current HIRAX antenna design were performed in an anechoic chamber and compared to simulations. We report measurement techniques and results, which find a broad and symmetric antenna beam for ν<650MHz, and elevated cross-polarization levels and beam asymmetries for ν <700MHz. Noise temperature measurements of the HIRAX feeds were performed in a custom apparatus built at Yale. In this system, identical loads, one cryogenic and the other at room temperature, are used to take a differential (Y-factor) measurement from which the noise of the system is inferred. Several measurement sets have been conducted using the system, involving CHIME feeds as well as four of the HIRAX active feeds. These measurements give the first noise temperature measurements of the HIRAX feed, revealing a ∼60K noise temperature (relative to 30K target) with 40K peak-to-peak frequency-dependent features, and provide the first demonstration of feed repeatability. Both findings inform current and future feed designs.
© (2022) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Emily R. Kuhn, Benjamin R. B. Saliwanchik, Kevin Bandura, Michele Bianco, H. Cynthia Chiang, Devin Crichton, Meiling Deng, Sindhu Gaddam, Kit Gerodias, Austin Gumba, Maile Harris, Kavilan Moodley, Mugundhan V., Laura Newburgh, Jeffrey Peterson, Elizabeth Pieters, Alexandre Refregier, Ajith Sampath, Mario G Santos, Onkabetse Sengate, Jonathan Sievers, Ema Smith, Will Tyndall, Anthony Walters, Amanda Weltman, and Dallas Wulf "Antenna characterization for the HIRAX experiment", Proc. SPIE 12182, Ground-based and Airborne Telescopes IX, 1218225 (26 August 2022); https://doi.org/10.1117/12.2627856
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KEYWORDS
Antennas

Temperature metrology

Amplifiers

Optical testing

Polarization

Nitrogen

Optical simulations

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