An efficient electric field approximation for spiral inflector calculations

This paper presents a new analytical approximation of the electric field in the spiral inflector. It is based on R-function formalism and derived according to the geometric shape of the inflector including the grounded electrodes. A comparison against finite difference solution is given in order to illustrate the validity of the approximation. Also, the results of stochastic ion beam simulation are presented. They clearly show that the proposed approximation yields a very good agreement with the real electric field.