Alternative optics design for the ALMA band 1 receiver (35–52 GHz)

The Atacama Millimeter/Sub-millimeter Array (ALMA) is one of the most powerful telescopes built to date. All the receivers that cover the 10 frequency bands (35-950 GHz) in ALMA must comply with stringent requirements in order to perform astronomical observations, in particular, low noise temperature and high aperture efficiency. The ALMA band 1 receiver optics (35-52 GHz) are composed of a corrugated horn antenna and a dielectric lens. They have proved difficult to design because of the large bandwidth to cover and truncation effects in cryostat apertures. This paper presents a design which meets the stringent ALMA requirements.