A Submillimeter Cartridge-Type Receiver: ALMA Band 8 (385--500 GHz) Qualification Model

We have developed a cartridge-type receiver covering the frequency band of 385-500GHz as a qualification model of Atacama Large Millimeter/submillimeter Array (ALMA) band 8. It receives two orthogonal polarizations and down-converts the sideband-separated signals to intermediate frequencies (IF) of between 4 and 8GHz. The cartridge-type receiver consists of cold optics, two feed horns, a wire grid, mirrors, two sideband-separating SIS mixers, cryogenic multipliers of a local oscillator (LO), cryogenic and warm IF amplifiers, a cartridge body, and sensors/wirings. These components were individually tested, and then the cartridge was integrated and tested as a complete assembly. We have also developed equipment for efficiency tests of both the components and the integrated receiver. The single sideband (SSB) noise temperature of this receiver is 100K at the band center and 300K at the band edges. The beam pattern and cross-polarization pattern are consistent with a physical optical calculation. The amplitude stability is around 3 x 10(-4) in 1 s. The phase stability is less than 2.degrees 0 on a time scale of 0.1 s to 10 min. These results are promising for a receiver in the ALMA.