Cryogenic Frontend work for the 12m telescope entering phase II

Figure 2: (Left) The Quadruple-Ridged Flared Horn (QRFH) with room temperature low noise amplifier. (Right) QRFH mounted on the 12m telescope for performance measurements.

Efforts to build a wideband (2.5 to 14 GHz), cryogenic front-end for the 12m telescope are steadily progressing. CryoElec, LLC, Arizona, in consultation with the Arecibo engineering team and scientists in the astronomy group is designing and building the system. During phase I of the project, parts for a custom Quadruple-Ridged Flared Horn (QRFH) were precisely machined and assembled at CryoElec. The measurements made on the horn showed excellent return loss (~ -10 db) and cross polarization performance (< -30 dB) over the frequency range 2.5 to 14 GHz. The assembled QRFH with a custom made room temperature amplifier were brought to Arecibo Observatory and installed on the 12m telescope in early June, 2022 (see Fig 2). The hot/cold load measurements on the ground provided receiver temperatures close to the expected value. On telescope measurements provided a spillover temperature between 18 and 7 K at 8 GHz for different focal distance offsets (offsets of a few inches from the nominal focal point). Based on these measurements the project will be moving forward to phase II, which includes the construction of the cryostat, the full receiver system, the control modules and the installation of the receiver on the telescope.