A three photon noise SIS heterodyne receiver at submillimeterwavelength

摘要

An ultra-low noise single sideband SIS receiver has been prepared for radio astronomy at the sub millimeter wavelength λ≈0.85 mm. The minimum single sideband receiver noise temperature of 48 K corresponds to 3 hω/k or equivalent number of 3 photon of noise. The minimum single sideband SIS mixer noise temperature is about 20 K, close to 1.2 hω/k, or one photon of noise. The Nb/AlOx/Nb junctions with a Josephson critical current density of 9 KA/cm2 and with the area of about 0.9 μm2 were used. The receiver has been tested at the 30 meter IRAM radio telescope in the winter seasons of 1997 and 1998. The observations at the radio telescope are speeded up by a factor of two to three with the new receiver