ALMA Band 5 Receiver Cartridge Cold Cartridge Assembly

Other conference contribution, 2010

ALMA, Atacama Large Millimetre / Sub-millimetre Array, covers the frequencies from 30 to 960 GHz in ten separate frequency bands. One of the bands, Band 5, is assigned to the RF band 163 – 211 GHz. Band 5 receiver is the lowest ALMA frequency band using all-cold optics. This implies large-rim mirrors placed inside a limited space of the receiver cartridge living very little space for the receiver components. Consequently, besides achieving the state of the art receiver performance, ALMA Band 5 receiver cartridge design faces the challenge of fitting the required components of the two-polarization sideband separation receiver into the optics squeezed space. Band 5 cartridge pursues a modular design; the sideband separation (2SB) SIS mixer uses two DSB mixers made in the end-piece configuration. The orthomode transducer (OMT) serves as a polarization splitter, with the two 2SB mixers placed at the both sides of the OMT with the mixer IF outputs pointed along the vertical axis of the cartridge. This layout allows placing the IF chain in between the 4 and 15 K plates of the receiver cartridge. At the Workshop, we present details on the design and the optics, noise temperature (achieving hf/6k) and sideband separation measurements of the ALMA Band 5 cold receiver cartridge.