Physics of JLab FEL injector

Jefferson Laboratory is currently commissioning a high-power kw-level cw IR FEL which recently demonstrated impressive high-power capability with the linac operating in a nonrecirculating mode. The injector, which provides a 10 MeV electron beam with high bunch charge (60--135 pC) to the linac, consists of a 350 kV dc photocathode gun and two 5-cell superconducting rf cavities, along with a buncher cavity. Due to the nonrelativistic nature of the electron beam at 350 keV there is some interesting physics involved in the beta=1srf cavities during acceleration. This is discussed, as is the usual space-charge-originated emittance degradation at various injector components