A Collimated Total Radiation Probe for Arcjet Measurements

The total energy radiation of an argon arcjet was measured by a simple collimated thermopile. Radiation from the luminous jet was found to vary as T7.2 when the peak (centerline) temperature at the arcjet exit plane was 12,600°K. Total radiated energy from the arcjet, including the downstream-directed component from the cathode face, was found to agree quite well with theoretical estimates given in the present paper. The use of a purified helium atmosphere and lithium fluoride optical components permitted achievement of transmissivity down to 1060 angstroms on all measurements.