Ion Energy Distribution at the Wall of a Non-Thermal Plasma

Abstract

A combined mass spectrometer - probe diagnostic is applied to investigate the energy distribution of positive ions at the wall of a positive column in Argon. With a small wall probe, perforated for ion extraction, the probe characteristic, the A+-current versus probe potential, and the A+-current versus retarding potential are measured. Electron temperature from the probe characteristic and ion temperature from the last two characteristics agree within the experimental error. The Böhm criterion can be modified by T+ = Te at the wall. With a small wall probe the sheath only partly can be reduced; for positive probe potentials a potential wall in front of the probe is built up, which acts as an energy analyzer. Ion-neutral and ion-ion collisions cannot account for the Maxwellian distribution of the ions found experimentally