Transverse Effects Due to Vacuum Mirror of RF Gun

The transverse kick due to the vacuum mirror in the RF gun can negatively affect the beam emittance. In this contribution we estimate numerically and analytically the transverse wake function of the European XFEL RF gun and apply it in beam dynamics studies of the transverse phase space. INTRODUCTION An electron beam with low emittance and high peak current is required in the European Free Electron Laser [1]. To meet these requirements, a laser-driven photocathode radio frequency (RF) gun has been designed and studied both experimentally and theoretically at DESY. The vacuum mirror of the laser is a main source of the transverse kick on the axis. It could disturb an emmitance compensation mechanism of the gun [2] considerably. In this contribution we estimate numerically and analytically the transverse kick due to the mirror and apply it in beam dynamics studies of the transverse phase space. The codes ECHO [3] and PBCI [4] are used to calculate the kick. The code ASTRA [5] is used for beam tracking. TRANSVERSE WAKE FUNCTION Geometry of the vacuum mirror and the beam parameters The geometry and the main dimensions of the vacuum mirror are shown in Fig. 1. 18.5mm b = 12.4mm a = 2 20mm d =