Baryon acoustic oscillations from Integrated Neutral Gas Observations: Broadband corrugated horn construction and testing

Wuensche, C. A.; Reitano, L.; Peel, M. W.; Browne, I. W. A.; Maffei, B.; Abdalla, E.; Radcliffe, C.; Abdalla, F.; Barosi, L.; Liccardo, V.; Mericia, E.; Pisano, G.; Strauss, C.; Vieira, F.; Villela, T.; Wang, B.
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Experimental Astronomy

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The Baryon acoustic oscillations from Integrated Neutral Gas Observations (BINGO) telescope is a 40-m class radio telescope under construction that has been designed to measure the large-angular-scale intensity of Hi emission at 980-1260 MHz and hence to constrain dark energy parameters. A large focal plane array comprising of 1.7-metre diameter, 4.3-metre length corrugated feed horns is required in order to optimally illuminate the telescope. Additionally, very clean beams with low sidelobes across a broad frequency range are required, in order to facilitate the separation of the faint Hi emission from bright Galactic foreground emission. Using novel construction methods, a full-sized prototype horn has been assembled. It has an average insertion loss of around - 0.15 dB across the band, with a return loss around 25 dB. The main beam is Gaussian with the first sidelobe at around - 25 dB. A septum polariser to separate the signal into the two hands of circular polarization has also been designed, built and tested.