New developments in the radiance calibration of deuterium lamps in the UV and VUV spectral range at the PTB

Abstract

The Physikalisch-Technische Bundesanstalt (PTB) operates a unique beam line for the radiometric calibration of ultraviolet (UV) and vacuum-ultraviolet (VUV) radiation sources by direct comparison of their unknown spectral radiant flux with the calculable spectral radiant flux of the electron storage ring BESSY I in the spectral range 40 nm to 400 nm. At this beam line the relative standard uncertainty of the calculated spectral radiant flux of the synchrotron radiation is u = 3 × 10−3 and it allows the calibration of the spectral radiance of deuterium lamps with a relative standard uncertainty of 2.5 × 10−2 above 165 nm. The high-accuracy beam line is now complemented by new instrumentation specially designed for the dissemination of the spectral radiance and radiant intensity scale using deuterium lamps as transfer source standards. This instrumentation allows the calibration of radiation sources in the 115 nm to 400 nm spectral range without significant loss in accuracy and the measurement of spectrally and spatially resolved radiance profiles such as to image the plasma topography of the discharge. The new instrumentation is described. Results for the radiometric long-term stability of selected deuterium lamps are shown. The radiance and radiant intensity as well as the radiance profile of different types of commercially available deuterium lamp are presented.