THE TESLA-FEL DEVELOPMENT PROJECT:FROM VUV TO X-RAY FREE-ELECTRON LASERS

Gerhard Materlik

Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron DESY Notkestr. 85, D-22603 Hamburg, Germany

After several of third generation synchrotron radiation light sources have come in operation extraordinarily successfull over the past decade, discussions about possible candidates for fourth generation synchrotron radiation light sources have centered on Free Electron Lasers driven by linear accelerators.

This combination seems to be the most promising candidate especially when a large flexibility is reached by using the self amplified spontaneous emission SASE excited by single path long undulators.

The spectrum from such free electron laser contains the FEL lines and additionally also the continuous spectrum of spontaneous emission from the undulator. This combination is of special interest in the X-ray regime.

In comparison to third generation sources the average brilliance can be 3-5 orders of magnitude higher, the peak brilliance due to the short bunch length in the order of fs to ps provides extraordinary high gains of possible 10 orders of magnitude.

At DESY the TESLA-FEL project consists of phase 1 where the principle of SASE should be tested at wavelength ranging from 400 to 1200 Å. Phase 2 should extend this range to 60 Å and a third step could possibly extend the wavelength region down to 1 Å in connection with the long linear collider proposed for high energy physics.

The present status and also some possible applications will be discussed.