Using rational surfaces to improve pellet fuelling in stellarators

Pellet injection is currently the primary candidate for achieving efficient plasma fuelling, one of the key issues for steady-state operation in large fusion devices. In this paper, pellet injection experiments are performed for several magnetic configurations of the TJ-II stellarator. The aim of th...

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Bibliographic Details
Published in:Journal of plasma physics 2023-11, Vol.89 (6), Article 955890601
Main Authors: Panadero, N., McCarthy, K. J., Pégourié, B., Carrasco, R., García-Cortés, I., García, R., Hernández-Sánchez, J., Köchl, F., Martínez-Fernández, J., Sakamoto, R.
Format: Article
Language:English
Subjects:
Ablation
Configurations
Damping
Deposition
Drift
Homogenization
Injection
Magnetic fields
Pellets
Plasma
Plasma physics
Stellarators
The 23rd International Stellarator-Heliotron Workshop (ISHW)
Tokamak devices
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Summary:Pellet injection is currently the primary candidate for achieving efficient plasma fuelling, one of the key issues for steady-state operation in large fusion devices. In this paper, pellet injection experiments are performed for several magnetic configurations of the TJ-II stellarator. The aim of this study is to increase the understanding of the role played by rational surfaces in plasmoid drift and deposition profiles in stellarators. The analysis of experimentally observed plasmoid drifts is supported by simulations of such cases made with the HPI2 code. Plasmoid drift is found to be significantly reduced, as in tokamaks, in the vicinity of rational surfaces. This is attributed to the fact that plasmoid external charge reconnection lengths are shorter near rational surfaces, resulting in a more effective damping of the plasmoid drift. Although the effect of plasmoid external currents on the drift is expected to be negligible in stellarators, compared with those caused by plasmoid internal currents, the effect observed in TJ-II is clearly measurable. In addition, simulations show that enhanced drift reductions near rational surfaces lead to significantly different deposition profiles for the magnetic configurations included in this study. This implies that it should be possible to select the magnetic configurations to obtain more efficient pellet fuelling.
ISSN:0022-3778
1469-7807
DOI:10.1017/S0022377823001010