On emittance evolution in the extraction system of high-current electron and ion sources

A simple model has been built to study the evolution of high-current electron or ion beams in axially symmetric extraction systems (electron guns or ion sources). Both electric and magnetic field components induced by a HV diode and a focusing solenoid respectively are computed using analytical formulas. The space-charge forces are computed using a ring method. In a first step, the individual effects of the 3 nonlinear forces (electric, magnetic and space charge) on the emittance evolution are presented. We then discuss how the knowledge acquired in the first step can be used to understand and optimize the emittance evolution in systems combining these effects.