New Millimetrewave Receivers at NRAO

A new generation of low-noise, dual-polarisation receivers covering the atmospheric windows between 65 GHz and 300 GHz is nearing completion. These receivers use niobium junction SIS mixers which have proven to be very sensitive and reliable. A modular approach has been used and each receiver channel is constructed as an insert which is mounted in a stainless-steel dewar cooled by a closed-cycle 4K refrigerator. Several frequency bands may be accommodated in a single package. Currently, a 65-116 GHz receiver with noise temperatures typically <1OOK SSB, a 130-170 GHz with noise temperatures typically <200K, and a 200-270 GHz receiver with noise temperatures typically <200K SSB are operational. A 260-300 GHz insert is under construction.