The Transformation of the TESLA Test Facility into the VUV FEL User Facility at DESY

Gamp, Alexander

Report

PUBDB-2018-03301

The Transformation of the TESLA Test Facility into the VUV FEL User Facility at DESY

Gamp, A. (Corresponding author)DESY*

2004

5 pp. (2004)

Report No.: TESLA FEL 2004-07

Abstract: After the end of the very successful operation of theTESLA Test Facility in November 2002, the modificationof TTF into a VUV FEL user facility took place duringthe years 2003 and 2004. The injector complex wascompletely modified. By the beginning of this year 5cryomodules were installed and the vacuum system wasclosed. For bunch length measurements there is a specialS-band structure driven by a SLAC 5045 Klystron and anElectro-Optical-Sampling Experiment. Six undulatormodules of 30 m total length have also been installed.Until May 2004 the five cryogenic modules and their rfpower input couplers were conditioned up to full rfpower. In one cavity of the first module an acceleratinggradient of 35 MV/m with beam could be demonstrated.The last module (No.5) can be reliably operated at anaverage gradient of 25 MV/m.So far, beam has been sent only through the firstmodule and through the first bunch compressor. Firstemittance measurements show values around 3 pmmmrad.In the second half of this year completion ofinstallation of technical components like power supplies,beam diagnostic elements etc. took place prior to fullcommissioning of the entire machine which started in the beginning of September saturation of the SASE gain was obtained in the entireFEL wavelength range of 80 – 120 nm [4].The necessary conditions which had to be fulfilled inorder to obtain these results were the acceleration ofelectron bunches with high peak current and lowemittance and the high field quality in the undulatormagnets [5]. Under these circumstances there wasinteraction between the photons and the electron bunchesduring the entire passage through the undulator which ledto microbunching and finally gain saturation.Since 1997 until November 2002, where TTF Ioperation ended, 15000 hrs. of beam time wereaccumulated. During the last two years about 50% of thetime was allocated to FEL operation including a largepercentage of scientific user time.After the end of TTF I its transformation into the VUVFEL user facility began immediately. To reach saturationat the minimum design wave length of 6.4 nm the energyof the electron bunches must be increased to 1 GeV andthe magnetic length of the undulators has to be doubled tosix undulator segments with a total length of almost 30 m.Besides a new injector, an additional bunch compressorand 5 cryogenic modules, which have been installed sofar, ultimately the installation of a third harmonic rfsystem, a seeding monochromator and an additionalcryogenic module are planned .

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