Control for fusion thermal stability

A review of the literature on the problem of fusion thermal stability shows that many control mechanisms have been proposed and analyzed which permit operation of the plasma thermal balance in otherwise unstable temperature regimes. Certainly stability is a necessary condition for operation, but perturbations in component parts, and system disturbances will additionally require that the integrated system possess certain desirable characteristics and properties, such as acceptable overshoot, adequate speed of response, etc. This work represents an analysis of the thermal balance of a fusioning plasma from a control system perspective. By applying the techniques of classical control theory, in addition to determining the requirements for stability, the response characteristics of the thermal balance have been evaluated. The results show that open-loop equilibria are characterized by restrictively narrow stable operating temperature regimes and generally poor system performance. The results also show that closed-loop proportional feedback using the fuel feedrate and injection energy can be used to extend the stable operating temperature regime and significantly improve the system response. Additional improvement is available using proportional-integral-derivative (PID) control