Characterization and validation of a new cryogenic radiometer at the LNE-LCM

The French National Metrology Laboratory, the LNE-LCM, uses a cryogenic radiometer as the basis for its optical radiation measurement scales. This instrument is an absolute radiometer operating at 4.2 K based on the electrical substitution method. It allows absolute measurements of the optical power of laser beams with a relative standard uncertainty in the range of 5 parts in 10⁵. A new cryogenic radiometer was installed in the laboratory and the present paper describes its complete metrological characterization which allows to achieve this level of uncertainty.