Bremen 2017 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 1: Plasma Diagnostics I

P 1.5: Vortrag

Montag, 13. März 2017, 09:45–10:00, HS 2010

Evaluation of new faraday probe designs employing RF ion sources and ion thrusters — •Maximilian Quaas, Frank Scholze, Ronny Woyciechowski, Christoph Eichhorn, Carsten Bundesmann, and Daniel Spemann — Leibniz Institute of Surface Modifcation, Permoserstr. 15, 04318 Leipzig

Faraday probes are indispensable tools for measuring the beam current density of ion sources or thrusters. However, a reliable determination of the positive ion current is not a simple task, but requires to take several effects into account, for example, the emission of secondary electrons and sputtered ions as well as the contribution of electrons from the neutralizer, if applicable, that can alter the measured beam current significantly. In order to account for these sources of uncertainties, new faraday cup designs, typically comprising a screen and a repeller electrode in front of the charge-sensitive cup, were evaluated using SIMION simulations. These simulations allowed to optimize the geometrical dimensions of the components as well as the voltage applied to the repeller electrode to ensure that sputtered ions as well as secondary electrons, respectively, do not leave and neutralizer electrons do not enter the cup. The optimized faraday cups were manufactured, tested and evaluated using Xe ions from a gridded RF ion source. The measured beam profiles recorded for several distances from the source were compared with a reference cup and the calculated total currents compared to the beam current for different repeller voltages.