HIGH-PRECISION ELECTRICAL SUBSTITUTION RADIOMETER BASED ON SUPERCONDUCTING-RESISTIVE TRANSITION EDGE THERMOMETRY

We describe the design and measured electrical performance of the firs t electrical substitution radiometer based on superconducting thermome ters. Prospective applications emphasize high precision measurement of low power, mid-and far-IR blackbody radiation. The minimum noise floo r for a single measurement of substitution power was 2 pW for an integ ration time of 2.7 a. For an extended series of experiments covering a range of substitution power from 0.5 nW to 5 mu W, the noise floor ca n be roughly approximated as 4 pW plus 7 x 10(-6) times the measured p ower. Analysis of the results indicates the precision is limited by a combination of thermal parasitics and electronic noise contributions.