Current plans to build a fusion reactor envision a tokamak-type device with tungsten plasma-facing components. The tokamak concept is based on magnetic confinement of the plasma, in which the magnetic field is generated by the combined contribution of electric current flowing in the magnetic coils and in the confined plasma. This dependence on the plasma current makes tokamak operation difficult, since plasma confinement relies on the control of plasma parameters. Sudden loss of plasma confinement, so called a disruption, is an important issue for tokamak operation safety. Uncontrolled disruptions can cause high thermal and mechanical stresses on plasma -facing components. One dangerous phenomenon is the generation of runaway electrons, which can lead to local melting of plasma-facing elements. Mitigation and control of runaway electrons is one of the important challenges in preparation for the operation of future fusion reactors.
During this seminar, an outcome of my PhD thesis will be discussed, namely a numerical analysis of tokamak disruptions with tungsten impurities. The goal is to determine the effect of tungsten on the evolution of the disruption, thermal and current quench times, and the production of runaway electrons. To achieve this goal, theoretical models of elastic and inelastic electron collisions with plasma impurities have been developed and implemented in the DREAM code, which has been used for numerical simulations.
