DARK CURRENT MEASUREMENTS AT THE PITZ RF GUN

For photocathode rf guns with electric fields of more than 40 MV/m at the photocathode and with an rf pulse length of 100 µs or more, the amount of dark current might be comparable with the photoelectron beam. At the pho-toinjector test facility at DESY Zeuthen (PITZ) the dark current was measured with a Faraday cup for various set-tings of the solenoid fields at the rf gun. We discuss the dark current behavior for different photocathodes. Experi-mental results are compared with simulations