Attenuated Superconductors I. For Measuring Infra-Red Radiation

Abstract

An apparatus for measuring infra-red radiation has been constructed of fine tantalum wire, operating at a temperature of 3.22–3.23°K in the transition zone between superconduction and normal conduction. The tantalum coil is mounted on a thermostated plate with temperature electrically controlled and operates in a special self-regulating shunt circuit by which its own temperature is automatically maintained constant. The ratio of developed electrical potential to radiation flux received is 150 μv (erg cm−2 sec.−1)−1. Minimum detectable flux is ca. 10−3 erg sec.−1. Absolute measurements of intensity of radiation from sources at temperatures between 24° and 55° are consistent with the Stefan-Boltzmann law showing that instrument corrections for reflectivity, window-absorption, and changes with wave-length are very small.