Erlangen 2026 – scientific programme
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P: Fachverband Plasmaphysik
P 8: Low Pressure Plasmas II
P 8.2: Talk
Tuesday, March 17, 2026, 16:45–17:10, KH 01.020
Systematic investigations of static and dynamic effects determining the performance of the ELISE negative ion source in H and D — •Joey Rubin, Dirk Wünderlich, and Ursel Fantz — Max Planck Institute for Plasma Physics - Boltzmannstrasse 2, 85748 Garching-bei-Munchen
The ELISE negative ion source is designed to meet the requirements of ITER’s NBI system: deliver high negative ion currents Iext in hydrogen (H)/deuterium (D) for up to 1h, keeping an acceptable co-extracted electron current Ie, high beam uniformity and low divergence.
A major challenge is the rapid rise of Ie during pulses, more pronounced in D (isotope effect). Previous campaigns showed that static (set directly by source parameters) and dynamic (time- and location-dependent plasma and surface processes, arising from the presence of Cs and its own behavior) effects contribute to the evolution of Ie. A mechanism explaining the observed increase of Ie was proposed, based on datasets collected over multiple campaigns with varying source configurations. A dedicated campaign was carried out in which ELISE was operated with full diagnostic coverage, stable caesium conditioning and closely matched driver plasma densities in H and D. Systematic scans of the operational parameters were performed for short (10 s) and long (300 s) pulses, enabling to separate static and dynamic contributions.
The results show that: the isotope effect is prominent in caesium density, extracted currents and beam divergence; the proposed mechanism for the dynamic rise of Ie is overall valid; beam divergence and uniformity do not simply correlate with plasma parameters.
Keywords: neutral beam injection; negative ion source; co-extracted electron current; isotope effect