Validating the simulation of beam-ion charge exchange in MAST Upgrade

Ollus, P; Allan, S; Harrison, J R; Jackson, A R; Kurki-Suonio, T; McClements, K G; Michael, C A; Moulton, D; Patel, B S; Robson, M; Snicker, A; Varje, J; Vincent, C

Abstract

Simulation of the impact of charge-exchange (CX) reactions on beam ions in the Mega Amp Spherical Tokamak (MAST) Upgrade was compared to measurements carried out with a fission chamber (neutron fluxes) and a fast ion deuterium-alpha (FIDA) diagnostic. A simple model was developed to reconstruct the outer-midplane neutral density based on measurements of deuterium-alpha emission from edge neutrals, and on Thomson scattering measurements of electron density and temperature. The main computational tools used were the ASCOT orbit-following code and the FIDASIM code for producing synthetic FIDA signals. The neutral density reconstruction agrees qualitatively with SOLPS-ITER modelling and yields a synthetic passive FIDA signal that is consistent with measurement. When CX losses of beam ions are accounted for, predicted neutron emission rates are quantitatively more consistent with measurement. It was necessary to account for CX losses of beam ions in simulations to reproduce the measured passive FIDA signal quantitatively and qualitatively. The results suggest that the neutral density reconstruction is a good approximation, that CX with edge neutrals causes significant beam-ion losses in MAST Upgrade, typically 20% of beam power, and that the ASCOT fast-ion CX model can be used to accurately predict the redistribution and loss of beam ions due to CX.

Citation

Ollus, P., Allan, S., Harrison, J. R., Jackson, A. R., Kurki-Suonio, T., McClements, K. G., …Vincent, C. (2024). Validating the simulation of beam-ion charge exchange in MAST Upgrade. Plasma Physics and Controlled Fusion, 66(2), Article 025009. https://doi.org/10.1088/1361-6587/ad15ed

• Journal Article Type: Article
• Acceptance Date: Dec 14, 2023
• Online Publication Date: Dec 28, 2023
• Publication Date: Feb 1, 2024
• Deposit Date: Jan 2, 2024
• Publicly Available Date: Jan 2, 2024
• Journal: Plasma Physics and Controlled Fusion
• Print ISSN: 0741-3335
• Publisher: IOP Publishing
• Peer Reviewed: Peer Reviewed
• Volume: 66
• Issue: 2
• Article Number: 025009
• DOI: https://doi.org/10.1088/1361-6587/ad15ed
• Keywords: FIDASIM, ASCOT, MAST Upgrade, neutron rate, neutral density, fast ions, passive FIDA
• Public URL: https://durham-repository.worktribe.com/output/2075739