Optical klystron

Fig. 10. Optical Klystron. Schematics of undulator and dispersive sections. The focused pulsed laser case is discussed in section 4.2.

Fig. 13. Calculated number of coherent photons produced, as a function of input laser energy, by an external laser = 3000 A focused into an optical klystron E = 400 MeV at SUPER-ACO.

In order to convert the undulator or optical klystron set-up to a PEL (Pig. 1), cavity mirrors of exceptional quality are required in the visible and ultraviolet regions. The technical problems of producing adequate, radiation resistant, mirrors have not yet been solved as will be seen shortly. 

Fig. 18. Comparison of undulator and optical klystron al, a2 Spontaneous emission bl, b2 laser induced electron bunch lengthening cl, c2 gain profiles at X = 4880 A and X = 5145 A respectively. Measurements as a function of undulator gap.

FEL experiments carried out at Orsay used the AGO characteristics given in table IV, the optical klystron parameters of table V and the two sets of optical cavity characteristics of table VI. Time structure and Q-switching studies have also been carried out (4a, 48). Orsay FEL performances in three sets of experiments (4c) are listed in table VII. 

The low power obtained with the PEL in the ACO storage ring is due to several limitations of this ring. It has a small diameter and a small space for insertion of an undulator or optical klystron (L = 1.3 m recall that the gain G is proportional to L ). Furthermore, at the low beam energies used for PEL operations the synchrotron power emitted is relatively small and the electron density is low (pg 22 2 x 10 electrons/cm ). The beam quality could be improved by the use of positrons rather than electrons in the storage ring. 

J. M. Ortega, Y. Lapierre, B. Girard, M. Billardon, P. Elleaume, C. Baziin, M. Bergher, M. Velghe, Y. Petroff Ultraviolet coherent generation from an optical klystron. IEEE J. QE-21, 909 (1985)... 

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