Research On Optimization Of Poloidal Field Coil Feeding In Fusion Reactors

Tokamak is by far the most promising way to achieve controlled fusion,it is of great significance to the development of clear energy in future.The poloidal field magnet system of a tokamak is a critical subsystem used for producing,maintaining and controlling the plasma current.The design of the current and feeding of the poloidal field coils is one of the basic subjects in the study of tokamak discharges.By analyzing the electromagnetic relationship between poloidal field coils and plasma current,this thesis studied the design of poloidal field coil currents for quasi-snowflake divertor discharges and alternating-current operation,and optimization of the feeding of poloidal field coils.The specific content and innovations are as follows:(1)The tokamak plasma equilibrium equations are derived,and the mathematical plasma current model is established.In addition,the parameters that affect the electromagnetic relationship between poloidal field coils and plasma currents are introduced in detail.(2)The control effect of poloidal field coils on plasma current configuration is studied.By solving the free boundary plasma equilibria problem with single coil current disturbance,the responses of plasma configuration and flux distribution to poloidal field coil currents are calculated.By fitting the response data of flux distribution to poloidal field coil currents,the flux response matrix is calculated,compared to the existing calculating method,it is more accurate.(3)The influence of plasma shape parameters on poloidal field coil currents is studied.The problem of PF coil currents exceeding the limits is solved by orthogonal experiments in the design of quasi-snowflake divertor discharges.It is found that it is possible to obtain the desired poloidal field coil currents by changing the plasma shape parameters.(4)A power supply design scheme incorporating coil distributed feeding and centralized feeding is put forward,compared to the coils powered by separated power supplies,the ability of poloidal field coils in controlling the vertical stability of plasma current is proved and the power configuration is significantly optimized through adding a quick response power supply to power multiple poloidal field coils together with the main power supplies.(5)The AC operation of tokamak is studied,and the method of constructing the plasma equilibria with reversed current density is presented,by changing the parameters of polynomial current model and solving the normalized G-S equation,different kind of equilibrium configurations with a zero total toroidal current have been constructed and the evolution of the equilibrium configurations of plasma current reversal has been designed.Take J-text tokamak as the example,the method of calculating the equilibrium of tokamak with iron core is studied.And a calculating program is developed to calculate the poloidal field coil currents.The research works in this dissertation lay a theoretical and technical foundation for the design of poloidal field coil currents and feeding of tokamaks.