Vacuum Variable-Temperature Blackbody VTBB100

The present state-of-the-art of precision radiometry based on the vacuum variable-low-temperature blackbody source VTBB100 developed for the low-background calibration facility at PTB is analyzed. This article describes the vacuum variable-low-temperature blackbody (VTBB) constructed to serve as a highly stable reference source for the calibration of blackbody sources in the temperature range from 100 K to 450 K under medium-vacuum conditions (10−3 Pa) in a medium-background environment (liquid-nitrogen-cooled shroud). The general concept and the design of the VTBB100 are given. The numerical investigation of the effective emissivity of the VTBB100 is performed. A description of the temperature control and measurement system of the VTBB100 is presented. Cooling of the VTBB100 is by liquid nitrogen. Heating of the VTBB100 is by a two-stage temperature control scheme. A thermal model of the radiator was developed. As a result of the analysis, it was shown that the system achieves an instability of the blackbody temperature of less than 20 mK. The characteristics of the blackbody operation—now at PTB—are described.