LASING AND RADIATION-MODE DYNAMICS IN A VAN-DE-GRAAFF ACCELERATOR-FREE-ELECTRON LASER WITH AN INTERNAL CAVITY

The lasing of a Van de Graaff electrostatic accelerator-free-electron laser (EA-FEL) with an internal cavity is reported. An EA-FEL employin g an internal cavity is a FEL configuration that has a potential to op erate at high average power, high frequency, and possibly in a continu ous wave (cw) mode. The initial lasing provided a pulsed radiation pow er of 1 kW at 100.5 GHz frequency. The FEL operated with a 1.4 A, 1.4 MeV electron beam in a recirculation (depressed collector) configurati on. It utilizes a high quality (Q approximate to 30 000) Talbot effect resonator and a Halbach-type wiggler placed internally in the center of the accelerator tank. Nonlinear features of the oscillation power b uildup and decay near saturation and mode hopping were observed and ar e interpreted. (C) 1997 American Institute of Physics. [S0003-6951(97) 03952-1].