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Plasma Potential and Energy Spread Determination Using Ion Beams Extracted from an Electron Cyclotron Resonance (ECR) Source

by Peter R Harris, Fred W Meyer
Publication Type
Conference Paper
Journal Name
Review of Scientific Instruments
Publication Date
Conference Name
13th International Conference on Ion Sources
Conference Location
Gatlinburg, Tennessee, United States of America
Conference Date

We have obtained estimates of plasma potentials and energy spreads characterizing an ECR ion source plasma under different source conditions. Our estimates are obtained from analysis of ion beams extracted from the ion source at 10 kV that are subsequently decelerated into a floating surface scattering chamber where their current intensity incident on a solid sample is measured as function of retardation voltage. The deceleration occurs outside the measurement chamber, permitting beam current measurements in a field-free region. Absence of grids in the deceleration section avoids potential issues of field penetration. The behavior of our deceleration optics was modeled with SIMION. The simulation indicated a linear beam attenuation dependence close to full retardation where the beam current goes to zero. Deviations from this linear dependence observed close to zero beam energy give information on the initial energy spread of the ions extracted from the source. Our decelerated beams measurements are compared with recent in-situ probe results and external beams results based on magnetic analysis.