Abstract
A collisionless plasma possesses a certain amount of 'available energy', which is that part of the thermal energy that can be converted into kinetic energy of plasma motion and electromagnetic fluctuations. In this paper we present a calculation of the available energy carried by trapped electrons in a slender non-omnigenous flux tube of plasma. This quantity is compared with gyrokinetic simulations of the nonlinear saturated radial energy flux resulting from turbulence driven by collisionless trapped-electron modes in various stellarators and a tokamak. The numerical calculation of available energy is fast and shows a strong correlation with the turbulent energy fluxes found in the gyrokinetic simulations. Indeed, the energy flux is found to be proportional to the available energy to the power of approximately, which is what one would expect from a simple argument. We furthermore investigate how available energy is distributed across different bounce wells, and it is found that deeply trapped electrons typically contribute most to the available energy. Finally, we investigate the dependence of available energy on gradient strength, and we find important differences between weakly and strongly driven regimes for stellarators and tokamaks.
| Original language | English |
|---|---|
| Article number | 905890513 |
| Number of pages | 26 |
| Journal | Journal of Plasma Physics |
| Volume | 89 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 13 Oct 2023 |
Bibliographical note
Publisher Copyright:Copyright © The Author(s), 2023. Published by Cambridge University Press.
Funding
The authors are grateful for the valuable discussions with, J.M. Duff, J. Ball, T. Görler, M.J. Pueschel, P. Mulholland, P. Costello, M.J. Gerard and E. Rodriguez. This work was partly supported by a grant from the Simons Foundation (560651, PH), and this publication is part of the project ‘Shaping turbulence – building a framework for turbulence optimization of fusion reactors’, with Project No. OCENW.KLEIN.013 of the research program ‘NWO Open Competition Domain Science’ which is financed by the Dutch Research Council (NWO). This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Program (Grant Agreement No. 101052200 – EUROfusion). 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.
| Funders | Funder number |
|---|---|
| Simons Foundation | 560651, OCENW.KLEIN.013 |
| European Commission | 101052200 – EUROfusion |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek |
Keywords
- fusion plasma
- plasma dynamics
- plasma nonlinear phenomena