OPTIMIZATION OF THE FELIX ACCELERATOR WITH RESPECT TO LASER PERFORMANCE

In this paper we discuss the performance of the FELIX accelerator in r elation to the laser performance. Over the past year, a number of impr ovements have been made to the accelerator, both to the hardware and t o the way in which it was operated, that have resulted in a reduction of the time needed to reach saturation from 9 to 3 mus. Energy spread and stability, both short and long term, and operational flexibility, an important issue for a user facility, are addressed. Surprisingly, ' 'best'' FEL performance is not obtained at the same operation point th at gives the smallest energy spread, which suggests that the electron bunch length is not fixed. Evidence is presented for the conjecture th at the non-isochronicity of the bend plays a major role. Measurements of enhanced spontaneous emission and of coherence between successive o ptical micropulses, indicating a spatial structure in the electron mic robunches on the scale of an optical wavelength, are also discussed.