Aachen PK 2003 – wissenschaftliches Programm
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P: Plasmaphysik
P 9: Plasma Physics
P 9.3: Vortrag
Dienstag, 18. März 2003, 16:10–16:30, FO4
DISRUPTION MITIGATION BASED ON A FAST GAS INJECTION — •Alexei Savtchkov1, Gabriella Pautasso2, Karl Heinz Finken1, and the ASDEX Upgrade team2 — 1IPP Forschungszentrum Jülich — 2Max-Planck-Institut für Plasmaphysik, Garching
Crossing the limits of a stable operation of a tokamak leads to a loss of plasma stability (to a disruption). Dangerous consequences of disruptions are a) a deposition of the stored energy on installation walls within a short time, b) mechanical stresses during the phase of the plasma current decay, c) a possible production of fluxes of electrons accelerated to energies of several tens of MeV (runaways).
The fast injection of a large amount of gas presents a means for disruption mitigation. An enhanced impurity radiation cools the plasma, distributing its thermal content over a surface of the vacuum vessel. A cold highly-resistive outer mantel, produced after the gas injection, reduces the induction of currents in inner elements and lowers mechanical loads. An additional increase in density is favorable for removing runaways.
Experiments with Helium, Neon and Argon carried out on ASDEX Upgrade (IPP Garching) with a fast high-throughput valve (IPP Jülich) are reported. An influence of a strong gas puff on the decay time of the plasma current and a reduction of mechanical strains of the vessel are shown. An attempt is made to model the energy balance throughout a disruption after the gas injection.