LBNL, Berkeley, California, USA
In linac driven free electron lasers, the final electron beam quality is constrained by the low energy (<100 MeV) beam dynamics at the injector. In this paper, we present studies and the optimized design for a high-repetition (>1 MHz) injector in order to provide a high brightness electron beam. The design effort is also extended to multiple modes of operation, in particular different bunch charges. The effects of space charge and low energy compression on the electron beam brightness are also discussed for the different modes.
LBNL, Berkeley, California, USA
PNPI, Gatchina, Leningrad District, Russia
NPS, Monterey, California, USA
APEX the Advanced Photo-injector EXperiment at LBNL is devoted to the development of a MHz-class repetition rate high-brightness electron injector for X-ray FELs. APEX is based on a novel room-temperature 186 MHz RF gun operating in CW mode in conjunction with high quantum efficiency photocathodes capable of the required repetition rates with commercial lasers. APEX is organized in 3 phases. Phase 0 includes the demonstration of several important milestones for the project. The gun must be conditioned at full RF power in CW mode; the vacuum performance, directly impacting the lifetime of photocathodes, needs to be characterized; and different photocathodes will be tested at full repetition rate at the nominal gun energy of 750 keV. In Phase I, a new suite of beam diagnostics will be added to characterize the electron beam at the gun energy and at full repetition rate. In Phase II, a pulsed linac will be added for accelerating the beam at ~30 MeV to reduce space charge effects and measure the brightness performance of the gun when integrated in an injector scheme. Phase 0 is presently under commissioning and the first experimental results from this phase are presented.
