Radiation Thermometry and Emissivity Measurements Under Vacuum at the PTB

A new experimental facility was realized at the PTB for reduced-background radiation thermometry under vacuum. This facility serves three purposes: (i) providing traceable calibration of space-based infrared remote-sensing experiments in terms of radiation temperature from  −173 °C to 430 °C and spectral radiance; (ii) meeting the demand of industry to perform radiation thermometric measurements under vacuum conditions; and (iii) performing spectral emissivity measurements in the range from 0 °C to 430 °C without atmospheric interferences. The general concept of the reduced background calibration facility is to connect a source chamber with a detector chamber via a liquid nitrogen-cooled beamline. Translation and alignment units in the source and detector chambers enable the facility to compare and calibrate different sources and detectors under vacuum. In addition to the source chamber, a liquid nitrogen-cooled reference blackbody and an indium fixed-point blackbody radiator are connected to the cooled beamline on the radiation side. The radiation from the various sources is measured with a vacuum infrared standard radiation thermometer (VIRST) and is also imaged on a vacuum Fourier-transform infrared spectrometer (FTIR) to allow for spectrally resolved measurements of blackbodies and emissivity samples. Determination of the directional spectral emissivity will be performed in the temperature range from 0 °C to 430 °C for angles from 0° to ±70° with respect to normal incidence in the wavelength range from 1 μm to 1,000 μm.