Optics Design and Verification for the APEX Swedish Heterodyne Facility Instrument (SHeFI)

摘要

In this paper, we present the design and verification of the receiver optics for the Swedish Heterodyne Facility Instrument (SHeFI) of the APEX telescope. SHeFI is placed in the telescope Nasmyth cabin A (NCA). The receiver is designed to carry up to 6 frequency channels of which four receiver channels have been designed, built and characterized: 211-275 GHz (Band 1); 275-370 GHz (Band 2); 385-500 GHz (Band 3); 1250-1390 GHz (Band T2). Bands 1, 2, and T2 were installed in the telescope during Spring 2008 and are currently in operation. The first three bands use 2SB SIS mixer technology and Band T2 employs HEB mixers in a waveguide balanced mixer configuration. The entire optics design was driven by the requirement of frequency independent illumination of the secondary with -12 dB edge taper and the limitations imposed by the receiver position in the NCA. The optical system is designed to provide coupling of the SHeFI receiver channels and PI instruments placed in NCA to the common optics of the telescope and cover the wide frequency range from 210 GHz to 1500 GHz. In the paper, the design approach, optimization, and verification are described.