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P: Fachverband Plasmaphysik

P 8: Poster: Low Temperature Plasmas I

P 8.16: Poster

Dienstag, 9. März 2010, 16:00–18:00, Lichthof

Langmuir probe characterisation in a cesiated high density negative ion source — •Loic Schiesko, Ursel Fantz, and NNBI -Team — Max-Planck-Institut für Plasmaphysik, 85748,Garching, EURATOM Assoziation

Development of a high power RF H⁻/D⁻ source for the ITER neutral beam injectors has been ongoing at IPP Garching for the past several years. The source is Cs seeded in order to increase the negative ion yield. Temporal evolutions (day to day operation) of Langmuir probe characteristics located in the neighborhood where negative ions are created are presented and show the influence of Cs and H⁻. Comparisons between probe characteristics obtained in the beginning of the measurement campaign (low cesium coverage, low H⁻ current and high electron to negative ion ratio) and the end of the campaign (high cesium coverage, high H⁻ current and low electron to negative ion ratio) show a whole decrease of plasma parameters and also of particle densities. Moreover, the onset of an ion-ion plasma will be shown. Finally, the interpretation of such I(V) characteristics will be discussed.