EXPERIMENTAL STUDIES OF MICROWAVE AMPLIFICATION IN THE ION-FOCUSED REGIME

Studies are reported of microwave amplification with an ion-focused el ectron beam drawn from an induction injector. A free-electron laser (F EL) operating at 9.4 GHz and employing ion-focusing within the interac tion region has achieved power in excess of 30 MW at 9.4 GHz, with a b eam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, wit h no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are noted: poor fre quency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed.