Modeling of glow discharge sources with flat and pin cathodes and implications for mass spectrometric analysis

A set of three-dimensional models for a direct current glow discharge in argon, developed previously in our group, is applied to analytical glow discharge cells with either flat or pin-type cathodes. Among other quantities, the densities of the plasma species are calculated and compared for these two cathode shapes. A comparison is also made for the computed argon and sputtered cathode (copper) ion currents leaving the glow discharge cell and entering the mass spectrometer, because this is of major interest from the analytical point of view. Finally, for the pin cell, the influence of sampling distance (i.e., distance between cathode pin and exit slit to the mass spectrometer) on the calculated plasma quantities is investigated.