RETRACTED ARTICLE: Prevention of Plasma–Surface Interactions by Control of Plasma Equilibrium in Large Aspect Ratio Tokamaks

Abstract

In tokamak plasma, impurities present a number of problems. One is the radiative power loss, principally due to line radiation from partially stripped ions. Another is fuel dilution. This arises because impurity atoms produce many electrons and, for a given plasma pressure, these electrons lake the place of fuel particles. At high concentrations impurities prevent the plasma being heated. This is particularly a problem during the plasma start-up phase since impurities radiate most strongly at low temperatures before they become highly ionized. Impurities can also lead to disruptions as a result of edge cooling and consequent current profile modification. On the other hand, these problems can be prevented by control of plasma equilibrium (which is defined by Grad–Shafranov (GS) equation). Numerous methods exist to solve the GS equation, describing the equilibrium of plasma confined by an axisymmetric magnetic field. In this paper, we have proposed a new numerical solution to the GS equation of an axisymmetric, transformed in cylindrical coordinates solved with the Chebyshev collocation method, when the source term (current density function) on the right hand side is linear. The Chebyshev collocation method is a method for computing highly accurate numerical solutions of deferential equations. We describe a circular cross section of tokamak and present numerical result of magnetic surfaces on the IR-T1 tokamak and then compare the results with an analytical solution.