Design of an RF Photo-Gun (PHIN)

In this note we show the results of the RF simulations performed with a 2-D electromagnetic code, SUPERFISH, and a 3-D code, HFSS, which allowed us to obtain the main characteristics such as the cavity dimensions and the axial field distribution. In the second part, simulations of the beam dynamics in the gun with the PARMELA code are summarised. We provide also some calculations of the beam-loading, i.e. the voltage induced by the beam itself inside the gun, which can severely limit the gun performance. In addition, vacuum aspects have been thoroughly investigated as, in previous experiments with RF photoinjectors at CERN the pressure has been found to increase dramatically at high levels of extracted charge (≈1 µC).