Desert STAR: A 7 pixel 345 GHz heterodyne array receiver for the Heinrich Hertz Telescope

DesertSTAR is a 7 beam, 345 GHz heterodyne array receiver for the Heinrich Hertz Telescope (HHT) on Mt. Graham, AZ. The instrument uses fixed-backshort Superconductor-Insulator-Superconductor (SIS) mixers with a broadband waveguide probe. Instantaneous bandwidths greater than 2 GHz can be achieved over the entire 345 GHz atmospheric window. A cryostat with Joule-Thompson (JT) mechanical refrigerator allows continuous operation and 1.8W of cooling capacity at 4K, and provides the needed temperature stability for low-noise operation. Local Oscillator (LO) distribution is accomplished with a novel phase grating that yields high efficiency and power uniformity in a hexagonally symmetric geometry. The computer controlled bias system is an evolution of a proven design that is simple, portable to any computer platform, and easily extensible to over 100 channels. It provides control and monitoring of bias, temperature and vacuum from any X-windows capable machine, and writes an instrument status web page visible with any web browser. The 2 GHz Intermediate Frequency (IF) bandwidth allows the future addition of a wideband backend optimized for extragalactic observations, with ∼1700 km/s of velocity coverage. We present measurements of receiver performance and plans for integration on the HHT.