Superconducting RF photoinjector for light source and FEL accelerators

Abstract

A high average current photoinjector is required to delivery high brightness electron bunches for many proposed light sources and free electron laser (FEL) based facilities. A possible solution to provide such high brilliance sources might be a Superconducting RF (SRF) gun. In order to match into the accelerator, the gun has to be operational at L-band frequencies (1.3 GHz or 1.5 GHz) or a harmonic of this frequency. The development of a high current RF gun based on the TESLA type technology (1.3 GHz) has been carried out. For the Next Light Source Project, a suitable design Free Electron Laserhas been developed to provide the full specification for the machine. Further studies of the acceleration technique is being carried out to fully understand the optimum beam parameters. An overview of the requirements, system design and injector performances is offered. Optimisation of the launch cavity was carried out to achieve CW beam properties; Average beam current 100 mA, nominal beam energy of 10 MeV, with bunch parameters of 1 1 π.mm.mrad, 20 ps bunch length, and RMS energy spread of 0.1%. As was required by the 4 GLS light source design, whilst similar properties have been proposed for the NLS, a pulsed FEL light source. These studies have provided an indication as to the fully optimum shape of the launch cavity as a function of the machine requirements. These concepts will also be presented. (3 pages)