Mitigation of disruptions in a tokamak by means of large gas injection [Elektronische Ressource] / vorgelegt von Alexei Savtchkov

MITIGATION OF DISRUPTIONS INA TOKAMAK BY MEANS OF LARGE GASINJECTIONI n a u g u r a l - D i s s e r t a t i o nzurErlangung des Doktorgrades derMathematisch-Naturwissenschaftlichen Fakult˜atder Heinrich-Heine Universit˜at Dusseldorf˜vorgelegt vonAlexei SavtchkovausNowosibirsk, RusslandForschungszentrum Julic˜ h2003Gedruckt mit der Genehmigung der Mathematisch-Naturwissenschaftlichen Fakult˜atder Heinrich-Heine Universit˜at Dusseldorf˜Referent: Prof.Dr.U.SammKorreferent: Prof.Dr.G.PretzlerTag der mundlic˜ hen Prufung:˜ 02.02.2004A.Savtchkov"Mitigation of major disruptions in a tokamak by means of agas injection"ABSTRACTIn a tokamak, the poloidal magnetic fleld provided by the toroidal plasma currentforms an essential part of the fleld conflning the plasma. However, instabilitiesof the magnetohydrodynamic equilibrium can lead to an uncontrolled sudden loss of theplasma current and energy, which is called a disruption.During disruptions the plasma energy is typically deposited on the vessel walls within0:1 ms resulting in high heat loads and possible melting or evaporating of in-vessel com-ponents. The interaction of halo currents caused by displacements of the plasma columnwith the magnetic fleld results in j £ B-forces which can lead to structural damages.The increased loop voltage can give rise to the appearance of multi-MeV electron beams,so-called runaway electrons, which cause local damage when hitting the vessel wall.