An upper pressure limit for low-<i>Z</i> benign termination of runaway electron beams in TCV
Abstract We present a model for the particle balance in the post-disruption runaway electron plateau phase of a tokamak discharge. The model is constructed with the help of, and applied to, experimental data from TCV discharges investigating the so-called ‘low- Z benign termination’ runaway electron mitigation scheme. In the benign termination scheme, the free electron density is first reduced in order for a subsequently induced MHD instability to grow rapidly and spread the runaway electrons widely across the wall. We show that the observed non-monotonic dependence of the free electron density with the measured neutral pressure is due to plasma re-ionization induced by runaway electron impact ionization. At higher neutral pressures, more target particles are present in the plasma for runaway electrons to collide with and ionize. Parameter scans are conducted to clarify the role of the runaway electron density and energy on the free electron density, and it is found that only the runaway electron density has a noticeable impact. While the free electron density is shown to be related to the spread of heat fluxes at termination, the exact cause for the upper neutral pressure limit remains undetermined and an object for further study.
Authors
- O. Ficker (ORCID: https://orcid.org/0000-0001-6418-9517)
- S. Coda (ORCID: https://orcid.org/0000-0002-8010-4971)
- Benjamin Vincent (ORCID: https://orcid.org/0000-0001-5420-6002)
- L. Simons (ORCID: https://orcid.org/0000-0002-5838-5076)
- C. Colandrea
- H. Reimerdes (ORCID: https://orcid.org/0000-0002-9726-1519)
- C. Paz-Soldan (ORCID: https://orcid.org/0000-0001-5069-4934)
- B.P. Duval (ORCID: https://orcid.org/0000-0001-7783-129X)
- J. Decker (ORCID: https://orcid.org/0000-0003-0220-2653)
- M. Zurita (ORCID: https://orcid.org/0000-0002-9030-0423)
- C. Reux (ORCID: https://orcid.org/0000-0002-5327-4326)
- M. Hoppe (ORCID: https://orcid.org/0000-0003-3994-8977)
- P. Halldestam (ORCID: https://orcid.org/0000-0001-6471-2304)
- M. Lehnen (ORCID: https://orcid.org/0000-0001-6043-8803)
- M Pedrini (ORCID: https://orcid.org/0009-0007-8168-2312)
- U. Sheikh (ORCID: https://orcid.org/0000-0001-6207-2489)
- T. Wijkamp (ORCID: https://orcid.org/0000-0003-3110-8682)
- S. Jachmich (ORCID: https://orcid.org/0000-0001-8289-536X)
Institutions
- ITER (FR)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- CEA Cadarache (FR)
- Czech Academy of Sciences, Institute of Plasma Physics (CZ)
- Max Planck Institute for Plasma Physics (DE)
- Dutch Institute for Fundamental Energy Research (NL)
- École Polytechnique Fédérale de Lausanne (CH)
- Columbia University (US)
- Eindhoven University of Technology (NL)
- KTH Royal Institute of Technology (SE)
Publication Details
- Journal
- Plasma Physics and Controlled Fusion
- Published
- 2025-03-05
- DOI
- https://doi.org/10.1088/1361-6587/adbcd5
- Citations
- 2
- Primary Topic
- Magnetic confinement fusion research
- Type
- article
- Field-Weighted Citation Impact
- 3.74
Funders
- National Science Foundation
- U.S. Department of Energy
- EUROfusion
- European Commission
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- Euratom Research and Training Programme
- Staatssekretariat für Bildung, Forschung und Innovation
- Basic Energy Sciences