A comparison between the performance of split and integrated RF photoinjectors

RF photoinjectors, the present source of choice for production of ultra-high brightness electron beams, have two basic design types: split, in which a short, high gradient RF gun is followed by a a drift and a booster linac, and a lower gradient integrated photoinjector, in which the linac acceleration is connected directly to the gun. The first type is represented at UCLA by the Neptune photoinjector, the second by the newly constructed S-band PWT photoinjector. We examine, through simulation and theory, the relative merits of each type of injector, both from the point of view of the beam physics (ability of the source to produce high currents and low emittances), and of relative technical advantages