Performance and Uniformity of Mass-Produced SIS Mixers for ALMA Band 8 Receiver Cartridges

We developed SIS mixers for Atacama large millimeter/submillimeter array (ALMA) Band 8 (385-500 GHz) receiver cartridges and evaluated their performance. DC IV curves of the SIS mixers showed small leakage current at the high current density. The current density and quality factor (R_sg/R_n) of the Band 8 SIS junction were 13 kA/cm² and approximately 20, respectively. Double-sideband noise temperature of the 266 SIS mixers was 92.8 K at 4.0 K bath temperature on the average from 385 to 500 GHz with a standard deviation of 7.0%. A couple of sideband-separating (2SB) mixers for dual polarizations were used in the Band 8 receiver cartridge. The 73 receivers have met ALMA specifications of the noise temperature. Single-sideband noise temperature and image rejection ratio of the receivers were 139.5 K and 20.5 dB on the average from 385 to 500 GHz, respectively. These test results of the receivers indicate high quality and uniformity of the 2SB mixers.