Charge-exchange losses of beam ions in MAST Upgrade : experiments and modelling
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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18
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Plasma Physics and Controlled Fusion, Volume 67, issue 5, pp. 1-18
Abstract
Dedicated experiments were performed on MAST Upgrade to study beam-ion losses caused by charge exchange (CX) with edge neutrals. The fuelling was switched from the high-field side to the low-field side mid-discharge. Direct measurements suggest a strong increase in the neutral density around the plasma and a decrease in the beam-ion density, which is qualitatively explained by CX losses. Measurements by a resistive bolometer have suggested particle bombardment during neutral beam injection, providing a unique opportunity to separate CX from other loss mechanisms. To verify and quantify CX losses, the orbit-following code ASCOT, which accounts both for CX neutralization and reionization, was used to simulate beam-particle power loads on the bolometer. Simulations reproduce measured bolometer power loads during high-field-side fuelling, verifying CX losses of approximately 10% of the off-axis beam power. Toroidally symmetric simulations overestimate power loads on the bolometer during low-field-side fuelling, which is explained by toroidal asymmetry in the neutral density distribution, as is demonstrated by toroidally asymmetric simulations. Results suggest significantly higher CX losses during low-field-side fuelling, up to about 50% of off-axis beam power.Description
Publisher Copyright: © 2025. The Author(s). Published by the American Astronomical Society.
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Ollus, P, Kurki-Suonio, T, Lovell, J, McClements, K G, Michael, C A & Snicker, A 2025, 'Charge-exchange losses of beam ions in MAST Upgrade : experiments and modelling', Plasma Physics and Controlled Fusion, vol. 67, no. 5, 055039, pp. 1-18. https://doi.org/10.1088/1361-6587/adcae8