Design study for the RF photoinjector for the MIT-Bates X-ray laser

A multiple cell 1.3 GHz room-temperature photoinjector is under design for the MIT Bates X-ray laser project. The design features include tunable intercavity phase shifts allowing separate phasing of the cells for velocity bunching of the beam in the following drift, and optimization of cell shape for high shunt impedance and low wall power density. Beam dynamics are studied for charges ranging from 0.1 to 1 nC using a model, non-ideal laser profile shape. It is shown that collective effects at the high end of the range cause loss of beam brightness.