Study Of Plasma Discharge Characteristics In Ramp-up Phase For EAST Superconducting Tokamak

Control of plasma position plays an important role in plasma discharge of tokamak during a short period (10 to 150 milliseconds) after plasma breakdown. It affects plasma discharge success directly. Difficulty of control during this period is plasma being not equilibrium state, so it can not be explained by equilibrium theory.In this thesis, different motheds are used to calculate the vacuum field on the basis of optimized breakdown, then, a new method to feedback control the plasma discharge in the ramp-up phase is presented. High speed CCD is used as a diagnostic tool which records the whole process of plasma discharge. The change of plasma position and configuration with the time can be obtained from the recorded image. The plasma edge can be obtained by image processing approach. Matching many other diagnostic data, the optimized value of the poloidal field coils current at any time can be obtained by solving equations of the circuit models. It can keep the plasma discharge in stable state. In the whole control process, in view of the feedback control model, we analyze the principle for all the subsystems of the feedback control system. Two key parts for feedback control which are the calculations of both eddy current and magnetic field (the vertical magnetic field and the horizontal magnetic field) are elaborated. Then a specific method for feedback control during the period and the initial application of the model in experiment are given.Plasma boundary detection being an important part in the feedback control of plasma position, which has an important influence on the accuracy of the calculation results about eddy current and. magnetic field. In view of this, an adaptive detection algorithm for plasma boundary detection is proposed. The plasma boundary in the collected images is detected by using automatic classification. Then, a satisfactory result can be got by fitting the plasma boundary.Also, the fundamental equations required for the MHD equilibrium theory and typical EAST plasma equilibrium are presented. An equilibrium reconstruction interface program, using EFIT method, written in Matlab language, was applied to the experiment on EAST tokamak, and a preliminary result was got.