Thermal Measurements in Harsh Environments with Mm-wave and THz Radiometry

Temperature measurements in environments that preclude the use of conventional methods are possible with remote sensing of thermal emission in the mm-wave to THz range of frequencies. A 300-GHz radiometer is demonstrated to be an effective linear temperature sensor. Measurements with a THz blackbody source corroborate the nominal emissivity value of the target to be close to unity. The temperature inferred from radiometry measurements of a target with unknown emissivity is consistent with the physical temperature of the target. Field testing of the radiometer at a nuclear fusion facility for reactor-wall measurements is planned.