Beam-Based Procedures for RF Guns

A wide range of rf photo injector parameters has to be optimized in order to achieve an electron source performance as required for linac based high gain FELs. Some of the machine parameters can not be precisely controlled by direct measurements, whereas the tolerances on them are extremely tight. Therefore, this should be met with beam-based techniques. Procedures for beam-based alignment (BBA) of the laser on the photocathode as well as solenoid alignment have been developed. They were applied at the Photo Injector Test facility at DESY at Zeuthen (PITZ) and at the photo injector of the VUV-FEL at DESY at Hamburg. The field balance of the accelerating mode in the 1 1/2 cell gun cavity is one of the key beam dynamics issues of the rf gun. Since no direct field measurement in the half and full cell of the cavity is available for the PITZ gun, a beam-based technique to determine the field balance has been proposed. A beam-based rf phase monitoring proce dure has been developed as well.