VIRTUAL CATHODE DIAGNOSTICS WITH A LARGE DYNAMIC RANGE FOR A CONTINUOUS WAVE SRF PHOTOINJECTOR

摘要

In a laser driven electron gun the close relationship between the laser pulse parameters and the quality of the generated electron bunch requires a continuous monitoring of some of the laser parameters. A laser diagnostic system, called virtual cathode, controls the stability of the key laser parameters. Further, the virtual cathode allows to analyse the influence of laser instabilities on electron bunch parameters. The main challenge for the virtual cathode lies in covering the large dynamic range of the photocathode laser between commissioning at 120 Hz and operation at 1.3 GHz repetition rate. The design of the virtual cathode as well as first test measurements will be presented.