Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect

Journal Article · Wed Jun 15 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4953606· OSTI ID:22600118

Fukuyama, A. ^[1]; Yagi, M. ^[2]

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1. Department of Engineering, Kyoto University, Kyoto 615-8540 (Japan)
2. National Institutes for Quantum and Radiological Science and Technology, Aomori 039-3212 (Japan)

To study runaway electron generation in disruptions, we have extended the three-dimensional (two-dimensional in momentum space; one-dimensional in the radial direction) Fokker-Planck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a self-consistent manner. A particular focus is placed on the hot-tail effect in two-dimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electron-electron slowing down time for a few times of the pre-quench thermal velocity. It contributes to not only the enhancement of the primary runaway electron generation but also the broadening of the runaway electron distribution in the pitch angle direction. If the thermal energy loss during the major disruption is assumed to be isotropic, there are hot-tail electrons that have sufficiently large perpendicular momentum, and the runaway electron distribution becomes broader in the pitch angle direction. In addition, the pitch angle scattering also yields the broadening. Since the electric field is reduced due to the burst of runaway electron generation, the time required for accelerating electrons to the runaway region becomes longer. The longer acceleration period makes the pitch-angle scattering more effective.

• OSTI ID: 22600118
• Journal Information: Physics of Plasmas, Vol. 23, Issue 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DISTRIBUTION
DISTRIBUTION FUNCTIONS
ELECTRIC FIELDS
ELECTRON TEMPERATURE
ENERGY LOSSES
FOKKER-PLANCK EQUATION
INCLINATION
ION TEMPERATURE
ONE-DIMENSIONAL CALCULATIONS
PLASMA
RELATIVISTIC RANGE
RUNAWAY ELECTRONS
SCATTERING
SLOWING-DOWN
TAIL ELECTRONS
THREE-DIMENSIONAL CALCULATIONS
TWO-DIMENSIONAL CALCULATIONS