Phonon-cooled NbN HEB Mixers for Submillimeter Wavelengths

The noise performance of receivers incorporating NbN phonon-cooled superconducting hotelectron bolometric mixers is measured from 200 GHz to 900 GHz. The mixer elements are thin-film (thickness — 4 nm) NbN with —5 to 40 1= 2 area fabricated on crystalline quartz substrates. The receiver noise temperature from 200 GHz to 900 GHz demonstrates no unexpected degradation with increasing frequency, being roughly T Rx 1-2 K GHz -1 . The best receiver noise temperatures are 410 K (DSB) at 430 GHz, 483 K at 636 GHz, and 1150 K at 800 GHz.