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

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

doi:10.1088/1361-6587/ad15ed

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

P. Ollus^*, S. Allan, J. R. Harrison, A. R. Jackson, T. Kurki-Suonio, K. G. McClements, C. A. Michael, D. Moulton, B. S. Patel, M. Robson, Antti Snicker, J. Varje, C. Vincent, MAST Upgrade Team

^*Corresponding author for this work

Not published at VTT

Research output: Contribution to journal › Article › Scientific › peer-review

7 Citations (Scopus)

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.

Original language	English
Article number	025009
Journal	Plasma Physics and Controlled Fusion
Volume	66
Issue number	2
DOIs	https://doi.org/10.1088/1361-6587/ad15ed
Publication status	Published - Feb 2024
MoE publication type	A1 Journal article-refereed

Funding

We thank William Heidbrink and Christopher Beckley for helpful discussion. We acknowledge the contributions by Andrew Kirk and Andrew Thornton to the calibration of the fission chamber. The ASCOT simulations were carried out on the EUROfusion High Performance Computer, Marconi-Fusion, at CINECA. We acknowledge the computational resources provided by the Aalto Science-IT project. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion) and also with support from the EPSRC (Grant No. EP/W006839/1) and the US DoE Grant No. DE-SC0019007. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. This work was partially funded by the Academy of Finland Projects Nos. 324759, 328874 and 353370.

Keywords

ASCOT
fast ions
FIDASIM
MAST Upgrade
neutral density
neutron rate
passive FIDA

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1088/1361-6587/ad15ed

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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., & MAST Upgrade Team (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

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AU - Michael, C. A.

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AB - 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.

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

Abstract

Funding

Keywords

UN SDGs

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