FANATIC - AN SIS RADIOMETER FOR RADIO ASTRONOMY FROM 660 TO 695 GHZ

FANATIC is a compact radiometer optimized for radio astronomy from abo ut 660 to 695 GHz (lambdalambda 455 - 432 mum). We observed a large nu mber of molecular and atomic spectral lines from galactic and extragal actic sources during FANATIC's first run on the James Clerk Maxwell Te lescope in early March 1994. Double sideband receiver temperatures dur ing observations were about 800 K (25 hnu/k). The heart of the receive r is a two-junction Nb/AlO(x)/Nb SIS array fed by a sandwiched V-Anten na. The junction array and antenna are fabricated together at IRAM's G renoble SIS laboratory. Each junction has a normal resistance of R(n) approximately 10 OMEGA, an area of approximately 2 mum2, an individual radial stub circuit to resonate the capacitance, and a lambda/4 trans former to match to the antenna. The solid-state local oscillator is a mm-wave Gunn oscillator followed by a doubler and tripler. The LO dipl exer is a Martin-Puplett interferometer, which insures that there is a lways abundant LO power for operation and speedy tuning. The receiver and telescope coupling optics, LO, dewar, and calibration system fit o n an 0.6 x 0.8 m optical breadboard.