Photoemission studies and commissioning the ELSA-FEL experiment

Abstract The residual vacuum pressure of the 144 MHz RF-gun cavity has been improved significantly ( p r ≈ 5 × 10 −10 bar ). However, when running with RF power we still observe a vacuum degradation which is responsible for the limited photocathode lifetime. In the best conditions we have been able to work with a constant 5 nC charge per bunch during two hours. All the FEL components have been tested and we are assembling the machine which should be completed by the end of this year.