A Superconducting Tunnel Junction Receiver for 345 GHz

In this paper we discuss the design, fabrication, and testing of a quasiparticle tunnel junction receiver for use at 345 GHz. The design employs small area Nb/Nb-oxide/PbInAu edge junctions in order to keep the device capacitance small and maintain a modest value for ωRNC. For optimura noise performance and beam properties the mixer is contained in a waveguide mounting structure. Our best sensitivity was obtained at 312 GHz where we measured a double sideband (DSB) noise temperature of 275 K. Noise temperatures of 400 K (DSB) or better were obtained out to 350 GHz.