New UV spectral responsivity scale of the PTB based on a cryogenic radiometer and an argon plasma arc radiation source

A cryogenic-radiometer-based calibration facility utilizing monochromatized radiation of an argon arc plasma has been put into operation at the PTB. The high radiance of the plasma source allows us to improve the accuracy of the UV spectral responsivity scale between 200 nm and 410 nm and to achieve relative standard uncertainties of about 0.1% to 0.2%. Comparison with the PTB laser-based cryogenic radiometer at five laser lines in the UV indicated excellent agreement.