Equilibrium And Inversin Calculation For J-TEXT Tokamak Plasma

Tokamak plasma equilibrium is not only a basic but also a key problem in nuclear fusion study. During the discharge of the tokamak operation, proper feedback control is needed to configure many discharge parameters in order to get the optimal discharge result. Therefore the precise measurement of these parameters plays an important role in the plasma control. However, most of the parameters in the plasma discharge cannot be measured directly, such as the plasma configuration, safety factor profile and so on. How to reconstruct the plasma shape accurately has been one of the basic problems in tokamak operation, and it can be solved by the plasma equilibrium reconstruction and calculation.In tokamak operation, massive plasma equilibrium calculation is needed to reconstruct the plasma equilibrium rapidly and accurately. The plasma equilibrium focus on how to solve the Grad-Shafranov which is the basic equation on reconstructing the plasma equilibrium shape by the plasma measurement. The study of Grad-Shafranov equations is a basic and important job in the plasma equilibrium. The Grad-Shafranov equation has been deduced and several different methods are presented for solving the equation in this paper. The EFIT program which solves the equation by Green Function is applied for J-TEXT tokamak by the comparison among the methods. Then the structure and detailed use of EFIT is shown by the internal algorithm.Based on the fact that J-TEXT tokamak has an iron core transformer, a modified spool model is used for the plasma equilibrium reconstruction in EFIT. The discharge signals and magnetic measurement which were selected as useful signals for equilibrium calculation and reconstruction were achieved by an interface program named MDSPLUS. EFIT was used to study the evolution of the plasma equilibrium shape and other parameters during the discharge. The theoretical value of Shafranov shift which was the one of important plasma parameters was calculated by the electron cyclotron emission(ECE) measurement and the electron density measurement in the experiment. The comparison among the theoretical calculation, equilibrium calculation and experiment measurement was analyzed for providing essential data and evidences for experimental diagnostic measurement. The evolution of the plasma parameters was presented well by EFIT calculation. Through the experimental diagnostic measurement, it was proved that EFIT program could use for tokamak operation.