Electric field effects during disruptions
Tokamak disruptions are associated with breaking magnetic surfaces, which makes magnetic field lines chaotic in large regions of the plasma. The enforcement of quasi-neutrality in a region of chaotic field lines requires an electric potential that has both short and long correlation distances across the magnetic field lines. The short correlation distances produce a Bohm-like diffusion coefficient ∼Te/eB and the long correlation distances aT produce a large scale flow ∼Te/eBaT. This cross-field diffusion and flow are important for sweeping impurities into the core of a disrupting tokamak. The analysis separates the electric field in a plasma into the sum of a divergence-free, E→B, and a curl-free, E→q, part, a Helmholtz decomposition. The divergence-free part of E→ determines the evolution of the magnetic field. The curl-free part enforces quasi-neutrality, E→q=−∇→Φq. Magnetic helicity evolution gives the required boundary condition for a unique Helmholtz decomposition and an unfortunate constraint on steady-state tokamak maintenance.
- Research Organization:
- Columbia University, New York, NY (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Grant/Contract Number:
- FG02-03ER54696; FG02-95ER54333; SC0018424
- OSTI ID:
- 2567919
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 31; ISSN 1070-664X
- Publisher:
- American Institute of PhysicsCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Characterization of magnetic field lines in connection with the transport of field lines in Beltrami magnetic fields
Anomalous diffusion of field lines and charged particles in Arnold-Beltrami-Childress force-free magnetic fields