Optical klystron experiments for the ACO storage ring Free Electron Laser
D. A. G. Deacon;M. Billardon;P. Elleaume;J. M. Ortega;K. E. Robinson;C. Bazin;M. Bergher;M. Velghe;J. M. J. Madey;Y. Petroff;
To improve the gain in the Orsay storage ring Free Electron Laser (FEL) experiment, the 17 period permanent magnet undulator has been modified to form an optical klystron (OK). We report the measurement of spontaneous emission and the effects on it of energy spread and angular spread. Gain and laser induced bunch lengthening measurements with the OK are also reported and are in very good agreement with the FEL classical theory. The spontaneous emission spectrum which is easy to measure with good signal to noise ratio, turns out to be a very good diagnostic tool forenergy spread and angular spread measurements on storage rings. The factor China magnets of four increase in the small gain obtained by converting the undulator NOEL into an OK was the critical factor in the recent operation of the ACO storage ring laser above threshold.http://www.chinamagnets.biz
