ALMA band 2+3 (67–116 GHz) optics: Design and first measurements

The ALMA telescope is one of the largest on-ground astronomical projects in the world. It has been producing great scientific results since the beginning of operations in 2011. Of all the originally planned bands, band 2 (67–90 GHz) is the last band to be implemented into the array. Recent technological progress has open the possibility to combine bands 2 and 3 (84–116 GHz) into a single wideband receiver. This paper describes the first efforts to design wideband optics which cover both bands, from 67 to 116 GHz, using a profiled corrugated horn and a modified Fresnel lens. First measurements were performed at ESO in Dec15–Jan16 and showed good agreement with simulations.