DUAL-CHANNEL SIS RECEIVERS FOR THE IRAM PLATEAU-DE-BURE INTERFEROMETER

The five antennas of the Plateau de Bure Interferometer have been inst rumented with dual-channel receivers in the lambda 3 mm and lambda 1 m m bands. Polarisation diplexing allows simultaneous observations in th e two bands. Each receiver has ambient and cryogenic calibration loads , and one receiver is equipped with a beam switching chopper for total power flux measurements. Typically the receiver noise temperatures ar e < 50 K in both the lambda 3 mm band and the lambda 1 mm band. Initia l observations show that at 115 GHz the sensitivity is doubled compare d to the previous receivers, and high quality fringes have been obtain ed at 230 GHz. Preliminary experiments show that the receiver stabilit y is good enough to correct atmospheric phase variations by monitoring the fluctuations in atmospheric emission at 225 GHz. VLBI fringes hav e been detected between one 15-m antenna and the IRAM 30-m antenna in Spain.