Optimization of multi cell structure for cryogenic photocathode RF-guns

The cryogenic C-band photocathode RF electron gun operating at around 20K is under development at LEBRA in Nihon University. The RF gun consists of a 2.6 cell cavity with a resonant frequency of 5712 MHz. Though the π-mode 2.6-cell structure had been chosen in the early phase of the development, the number of cells has not been optimized for the property of the beam extracted from the RF gun. In this study, the dependence of the properties of the cavity on the length of the end cell where a cathode is attached has been simulated by using SUPERFISH. The property of the electron beam in each case has been estimated from the beam simulations using ASTRA. (author)