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Intensity monitor for free-electron lasers

In cooperation with DESY (Deutsches Elektronen-Synchrotron) in Hamburg and the Ioffe Institute, St. Petersburg, a detector for high-intensity vacuum UV-(VUV) radiation has been developed and calibrated at PTB's radiometry laboratory at the Berlin Electron Storage Ring BESSY II.

The VUV radiation detector exploits the photo-ionization of rare gases for measurement of the radiant power.

The detection principle is based on photo-ionization of rare gases and allows pulse-resolved detection of radiation with a temporal resolution of a few nanoseconds. The detector is linear over a wide range of radiant power because only a small fraction of the rare gas atoms is ionized – even at very high radiant powers – and because electrons and ions are detected without further amplification. Therefore, it could be calibrated with monochromatized synchrotron radiation at mean radiant powers of less than 1 µW and used on the VUV free-electron laser (VUV-FEL) at DESY for quantitative measurements of highly pulsed VUV radiation in the wavelength range around 90 nm with peak powers up to 150 MW.

As the detector is operated at a gas pressure of only 10-3 Pa, it is transparent to more than 99%. Therefore, the principle is presently being further developed and from 2005 on, four detection systems will start operation as online-intensity and beam position monitors for the DESY-VUV-FEL project. It will also be tested whether the detector can be used as a calibrated monitor detector for EUV radiation from pulsed plasma sources for microlithographic applications at 13 nm and for X-radiation on the Sub-Picosecond-Photon-Source (SPPS) at Stanford.

Contact at PTB:

Phone: +49-531-592-0