A BEAM LINE FOR RADIANT POWER MEASUREMENTS OF VACUUM ULTRAVIOLET AND ULTRAVIOLET SOURCES IN THE WAVELENGTH RANGE 40-400-NM

The Physikalisch-Technische Bundesanstalt (PTB) is operating a radiometric laboratory at the Berlin electron storage ring BESSY. In this laboratory a new instrumentation has been set up for the characterization of sources in the wavelength range from 40 to 400 nm. The spectral radiant power of the storage ring can be calculated from the knowledge of the storage ring parameters, allowing the use of BESSY as a primary radiometric standard source. The unknown spectral radiant power of a source under investigation is determined by comparison with the calculable spectral radiant power of BESSY. A concave mirror is imaging either the tangent point of the storage ring, or the vacuum ultraviolet source under investigation, into the entrance slit of a 1-m, 15-degrees McPherson-type monochromator. In order to account for the polarization property the complete optical instrumentation can be rotated around its optical axis. Measurements have been performed with the optical plane of the instrumentation parallel and perpendicular to the plane of the electron storage ring. The performance of this new beam line will be described. The polarization property, the influence of higher order radiation, and the spectral responsivity of the instrumentation are presented.