Recent Undulator and F.E.L. Experiments and Prospects at Lure

The recent experiments on the F.E.L. are described. The amplification of the emission emitted by the Optical Klystron and stored in the optical cavity has been demonstrated. An amplification of the stored emission by a factor of more than 2 is reported, indicating that the gain of the Optical Klystron is very close to the cavity losses ( 90 %). Plans to increase this gain include the use of an optimised electron energy (180 MeV), the injection of the ring with positrons and the construction of an additional high frequency RF cavity. Some prospects of the F.E.L. in the visible and U.V. regions on Super A.C.O. and D.C.I. are given. It is concluded that the electron beam properties and especially the maximum attainable electronic density are very crucial if one wants to reach the V.U.V. region. The mirror behavior under the very intense optical power delivered by the undulator on various harmonics should also receive a great concern.