Simulation of runaway electron generation during plasma shutdown by impurity injection
Licentiatavhandling, 2011

Disruptions are dangerous instabilities in tokamaks that should be avoided or mitigated. One possible disruption mitigation method is to inject impurities into the plasma to shut it down in a controlled way. Runaway Electrons (REs) can be generated after the plasma is cooled down by the impurities and these electrons can damage the tokamak. In this work a simulation code is developed to investigate different disruption mitigation scenarios. The response of the bulk plasma, more precisely the temperature evolution of electrons, deuterium and impurity ions are described by energy balance equations in a 1D cylindrical plasma model. The induction and resistive diffusion of electric field is calculated. RE generation rates are used to calculate the runaway current. The Dreicer, hot-tail and avalanche effect is taken into account and a simple model for RE losses is also included. RE generation is studied in JET-like plasmas during pellet injection. Carbon pellets cause effective cooling but these scenarios are prone to runaway generation. A mixture of argon and deuterium gas could be used for safe shutdown without RE generation. In ITER the hot-tail RE generation process becomes important, and the simulation is therefore extended to take this into account. Shutdown scenarios with different concentration of neon and argon impurities were tested in ITER-like plasmas. To simplify the problem the impurity injection into the plasma is not modeled in these cases, only the response of the bulk plasma. The avalanche process cannot be suppressed in a simple way and would produce high runaway current. It can be avoided if some runaway loss phenomenon is included in the simulations, like diffusion due to magnetic perturbations.

disruption mitigation

fusion plasma physics

impurity injection

runaway electron

tokamak

MC, Hörsalsvägen 5, Chalmers University of Technology, Göteborg
Opponent: Gergö Pokol, Institute of Nuclear Techniques, Budapest University of Technology and Economics, Hungary

Författare

Tamás Fehér

Chalmers, Teknisk fysik, Nukleär teknik

Runaway electron generation in tokamak disruptions

Plasma Physics and Controlled Fusion,; Vol. 51(2009)

Artikel i vetenskaplig tidskrift

Simulation of runaway electron generation during plasma shutdown by impurity injection in ITER

Plasma Physics and Controlled Fusion,; Vol. 53(2011)p. 035014-

Artikel i vetenskaplig tidskrift

Runaway electron generation during plasma shutdown by killer pellet injection

Plasma Physics and Controlled Fusion,; Vol. 50(2008)p. 055006-

Artikel i vetenskaplig tidskrift

Drivkrafter

Hållbar utveckling

Styrkeområden

Energi

Fundament

Grundläggande vetenskaper

Ämneskategorier

Fusion, plasma och rymdfysik

CTH-NT - Chalmers University of Technology, Nuclear Engineering

MC, Hörsalsvägen 5, Chalmers University of Technology, Göteborg

Opponent: Gergö Pokol, Institute of Nuclear Techniques, Budapest University of Technology and Economics, Hungary