The PTB high-accuracy spectral responsivity scale in the VUV and x-ray range

Abstract

At the electron storage ring BESSY II, the Physikalisch-Technische Bundesanstalt operates ten experimental stations at six synchrotron radiation beamlines for photon metrology in the spectral range from ultraviolet radiation to x-rays. Five of these beamlines are used to realize and disseminate a scale of spectral responsivity for photodetectors. Detector calibration is based on the use of cryogenic radiometers as primary detector standards. The current status of instrumentation and measurement capabilities is described. Best measurement capabilities (k = 2) for the calibration of photodiodes vary between 0.4% and 2.3%.

Gas detectors for x-ray lasers

“…35 We compared the X-GMD signal current measured with a Keithley 617 picoamperemeter to the output of a calibrated semiconductor photodiode as secondary standard for radiant power, traceable to a cryogenic radiometer as the primary detector standard. 17 As expected and indicated by the prominent L edges around 5 keV, the calibration curves clearly follow the xenon photoionization cross section ͓see Eq. ͑1͔͒.…”

“…a time constant of 20 s. The device was calibrated in the ion current mode at the laboratory of the PhysikalischTechnische Bundesanstalt ͑PTB͒, which is Germany's national metrology institute, at the electron storage ring BESSY II in Berlin, by using dispersed synchrotron radiation in the microwatt regime and a calibrated photodiode as a standard detector. 16,17 The resulting spectral responsivity s ion ͑ប ͒, which is defined as the ratio between the signal current I ion and the radiant power ⌽, may be expressed, at given photon energy ប , by the quantum efficiency QE ion ͑ប ͒ of the detector and the mean charge q͑ប ͒ generated per absorbed photon…”

Application of AXUV diode detectors at ASDEX Upgrade

“…The spectral responsivity of these diodes was measured at the synchrotron BESSY for photon energies between 50 eV and 1600 eV 17,18 . A calibration for VUV light with photon energies below 50 eV was not possible since the generated photocurrent was on the order of the dark current fluctuations (due to the low brilliance of BESSY in the VUV range).…”

UV and VUV calibration capabilities at the Metrology Light Source for solar and atmospheric research

“…Whereas for the wavelength range from 400 nm down to 40 nm a normal-incidence beamline (#4) is used [12], the range between 50 nm and 5 nm is covered by a grazing-incidence plane grating monochromator (#3). Both beamlines supply radiation with regard to highest spectral purity (by higher-order filtering) for typical tasks like detector calibration (detector-based) [13] and reflectance measurements [14], i.e. for the development of optical components in the context of industrial EUV lithography.…”