Numerical Analysis of Plasma Transport in Tandem Volume Magnetic Multicusp Ion Sources.

摘要

A one-dimensional fluid model of plasma transport in tandem volume magnetic multicusp ion sources is explored. The model, the positive ion source code Pos, by Glasser and Smith, calculates plasma density, drift velocity, electron temperature, and ion temperature in an ion source. The usefulness of the model is limited: (1) The plasma density trend runs opposite to experimental results, and electron temperatures are an order of magnitude higher than experimentally observed. (2) simplification of the reaction chemistry leads to a plasma balance between ionization and outflow instead of the correct balance between ionization and recombination. (3) Wall losses are neglected. (4) There are inconsistencies in the derivations of some equations. (5) The final solution depends on the choice of an initial estimated solution. (6) Results of the model are not totally reproducible. (7) Numerical instabilities develop upon modification of terms or variation of initial conditions outside of a narrow range. Calculations of the plasma potential from the results of the model are qualitatively correct.