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Current dynamics during disruptions in large tokamaks
L-G Eriksson1, P Helander, F Andersson
1Association EURATOM-CEA, CEA/DSM/DRFC, CEA-Cadarache, St. Paul lez Durance, France.
Physical Review Letters
|June 1, 2004
Summary
Self-consistent modeling shows that runaway electrons dramatically alter tokamak plasma current profiles during disruptions. Post-disruption, runaway electrons create a more peaked current, significantly increasing central current density in devices like JET and ITER.
Area of Science:
- Plasma physics
- Fusion energy research
- Disruptions in tokamaks
Background:
- Tokamak disruptions pose a significant challenge to fusion energy.
- Runaway electrons are generated during disruptions and can damage tokamak components.
- Understanding the evolution of plasma current during disruptions is crucial for reactor safety.
Purpose of the Study:
- To perform self-consistent modeling of plasma current evolution during tokamak disruptions.
- To investigate the generation and backreaction of runaway electrons on the electric field.
- To analyze the impact of runaway electrons on the post-disruption current profile.
Main Methods:
- Developed a self-consistent computational model.
- Incorporated runaway electron generation and their effect on the electric field.
- Simulated plasma current evolution for typical JET and ITER parameters.
Main Results:
- Plasma current profiles change dramatically during disruptions.
- Post-disruption current carried by runaway electrons is significantly more peaked than the thermal current.
- Central current density increases substantially due to runaway electrons, even with partial conversion.
- Radial runaway electron profiles can become filamented.
Conclusions:
- Runaway electrons play a critical role in shaping the post-disruption plasma current.
- The increased central current density poses a risk to tokamak operation.
- Filamentation of runaway electron profiles requires further investigation for predicting disruption effects.