SYNCHROTRON-RADIATION-OPERATED CRYOGENIC ELECTRICAL-SUBSTITUTION RADIOMETER AS THE HIGH-ACCURACY PRIMARY DETECTOR STANDARD IN THE ULTRAVIOLET, VACUUM-ULTRAVIOLET, AND SOFT-X-RAY SPECTRAL RANGES

The accuracy of detector calibration in the UV, vacuum-ultraviolet, an d soft-x-ray spectral ranges could be significantly improved by the us e of the synchrotron radiation electrical substitution radiometer (SYR ES) as the primary detector standard. The SYRES radiometer is optimize d for use with spectrally dispersed synchrotron radiation as supplied by two monochromator beam lines in the radiometry laboratory of the Ph ysikalisch-Technische Bundesanstalt at the Berlin electron-storage rin g (BESSY). Wavelength ranges from 0.8 to 25 nm and from 35 to 400 nm a re covered. The typically available radiant power of similar to 1-10 m u W can be measured with the SYRES radiometer with a standard relative uncertainty of less than 0.2%. The spectral responsivity of qualified photodiodes for use as secondary detector standards is determined by direct comparison with the primary detector standard at an arbitrary w avelength. At present, the scale of spectral responsivity is realized with a standard relative uncertainty of well below 1% in the spectral ranges 0.8-3.5 nm, 5-25 nm, and 120-400 nm. We provide a comprehensive description of the SYRES radiometer and of the two facilities for det ector calibration in the UV and vacuum-ultraviolet spectral ranges and in the soft-x-ray spectral range, respectively, and we discuss the ac hievable uncertainties in the calibration of detectors. (C) 1997 Optic al Society of America.