X-band ion-focused free-electron laser

Abstract To assess the feasibility of a free-electron laser two-beam accelerator (TBA/FEL), an induction driven FEL test stand in the X-band microwave regime has been constructed and the energy of the driving beam is being increased year by year. The FEL operating at 9.4 GHz and employing ion focusing even in the interaction region has achieved a power in excess of 30 MW and a gain of 20 dB/m for a 0.6 kA, 0.8 MeV beam. We have found that FEL performance is strongly limited by longitudinal space charge. To mitigate space charge effects, the injector of the test stand has been upgraded to 1.6 MeV and the FEL is under test operation. The outline of the test stand is described and its preliminary experimental results and expected performance are discussed.