A LOW-NOISE 665 GHZ SIS QUASI-PARTICLE WAVE-GUIDE RECEIVER

We report recent results on a 565-690 GHz SIS heterodyne receiver empl oying a 0.36mum2 Nb/AlO(x)/Nb SIS tunnel junction with high quality ci rcular non-contacting backshort and E-plane tuners in a full height wa veguide mount. No resonant tuning structures have been incorporated in the junction design at this time, even though such structures are exp ected to help the performance of the receiver. The receiver operates t o at least the pp frequency of Niobium, almost-equal-to 680 GHz. Typic al receiver noise temperatures from 565-690 GHz range from 160K to 230 K with a best value of 185K DSB at 648 GHz. With the mixer cooled from 4.3K to 2K the measured receiver noise temperatures decreased by appr oximately 15%, giving roughly 180K DSB from 660 to 680 GHz. The receiv er has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii.