MultiPac-multipacting simulation package with 2D FEM field solver

Abstract

MultiPac is a multipacting simulation package for analyzing electron multipacting in axisymmetric RF structures with TM 0nl mode, such as RF cavities, coaxial input couplers and ceramic windows. The package includes a graphical MATLAB user interface and a 2D finite element electromagnetic field solver with third order basis functions. The multipacting simulations are carried out by combining the standard electron trajectory calculations in the electromagnetic fields by the Runge Kutta method with the systematic searching and analyzing methods for multipacting resonances. In addition, in coaxial input couplers the program can treat standing, traveling and mixed waves. The simulations are carried out in three steps. First the program calculates the time harmonic electromagnetic fields in the given RF design. To this end an axisymmetric FEM field solver with an automatic mesh generator and eigenvalue solver has been developed. Then the program finds the multipacting field levels by tracking electron trajectories. Thirdly the program can locate and identify the multipacting trajectories. For the second and third step special counter and distance functions are applied.