Mitigation of disruption on IR-T1 tokamak by means of low-energy neutral beam injection to control runaway electron generation

Abstract

In a tokamak, the poloidal magnetic field provided by the toroidal plasma current forms an essential part of the magnetic field confining the plasma. However, instabilities of magnetohydrodynamic equilibrium can lead to an uncontrolled sudden loss of plasma current and energy, which is called a disruption. Disruptions are of significant concern to future devices due to the large amount of energy released during the rapid quenching of the plasma. One important consequence of disruption is the generation of significant current carried in multi-MeV runaway electrons that are eventually lost into plasma components. They can damage the tokamak walls and its structure if they are not controlled. Disruption control by neutral beam injection has been performed on IR-T1 to study the effect on runaway electron generated by plasma disruptions. Noble gases are used for injection, pure Hydrogen, Helium and Argon. The use of these non-reactive gases for disruption control ensures they fast removed from the vessel after the termination of a tokamak discharge. A piezo-valve is used for injection which has the precision of 1 ms. The effect of runaway electron generation control during disruption is studied using a comparison between reference disruptive discharge and a discharge into which different impurity species are injected. The data collected can then be used to optimize the performance of these energetic electrons control generated in disruption.