A 3-year project with partial EU funding† to develop a UV/VUV Free-Electron Laser (FEL) on ELETTRA, Europe’s first “third generation” high brightness synchrotron radiation source for the VUV/Soft X-ray region, began officialy on May 1st 1998. It is a collaboration between Sincrotrone Trieste (Italy), CEA/SPAM/LURE (France), CLRC-Daresbury Laboratory (England), the University of Dortmund (Germany), ENEA-Frascati (Italy) and Max-lab (Sweden).

The goals of the project are orientated towards its future use as a user facility, rather than in FEL development per se. The aims of the project are therefore to demonstrate:
- lasing over a broad spectral range from 350 nm to below 200 nm; although setting lasing wavelength records is not the primary goal of the project, extending operation below 200 nm is nevertheless of very great interest in order to extend the range of scientific possibilities for the utilisation of the radiation.
- operation of the laser while continuing to provide stable synchrotron radiation (SR) beams for other users; even though the operational energy and current will be lower than that in routine operation, the FEL mode is still of potential interest for a significant number of beamlines that do not require the highest photon energies and which in particular want to perform experiments that make use of the time structure of the radiation.
- use of the laser to perform pilot experiments both by itself and also in synchronism with SR from another beamline

We hope to meet these objectives, not only by means of the collaboration between European laboratories presently interested in SRFEL development, but through a combination of the following technical features:
- use of a high quality electron beam from a “3rd generation” synchrotron radiation source providing a low emittance and short bunch length and therefore a higher gain than in presently operating experiments
- operation at higher energy than existing experiments, providing the potential of higher power output and better compatibility with regular SR operation
- use of a helical undulator/optical klystron to reduce the power density of the spontaneous radiation and hence the degradation of the mirrors, as successfully demonstrated at UVSOR, as well as for increased gain compared to a linearly polarized device
- use of a sophisticated mirror chamber that will contain 3 remotely interchangeable mirrors to make the best use of the limited commissioning time, and also to allow a greater wavelength range to be covered for future experiments.

The predicted characteristics of the FEL radiation are given below:
 
 

Storage ring operation	1.0 GeV, 4 bunches
Tunability range	350 - 190 nm  3.5-6.5 eV
Average power	> 1 W
Pulse length (FWHM)	~ 5 ps
Peak power	> 40 kW
Pulse energy	>0.2 mJ
Photon flux	> 1018 photons/s (within the laser bandwidth)
Polarization	circular (linear may also be possible)
Repetition rate	4.6 MHz
Synchronization with synchrotron radiation	1:1

 

 Information on electron beam, undulator and optical cavity parameters can be found in hyperlink to FEL Parameters doucument. Further information on the project can also be found in the following publication:

R. P. Walker et. al., Proceedings of the 20th International FEL Conference, Williamsburg, VA, August 1998, Nucl. Instr. Meth. Phys. Res. A429 (1999) 179.

† partly funded under EC Contract ERBFMGECT980102