Fusion Science and Technology / Volume 37 / Number 2 / March 2000 / Pages 131-145
The temporal evolution of the operating point of a fusion plasma during the ignition access, during ignited and subignited operation phases, is analyzed for plasmas like that of the International Thermonuclear Experimental Reactor (ITER) on the basis of a one-half-dimensional set of equations including feedback equations for auxiliary heating and fuel supply. It is shown that simple proportional feedback controls do not work taking into account the delay times in the control process. Proportional-integral-differential (PID) and improved types of control are examined for the purpose of controlling a fusion plasma against sudden parameter changes. On this basis a study on the simultaneous use of D-T fuel injection and auxiliary heating control methods for an ITER-like plasma is carried out, resulting in an algorithm capable of finding the optimal operation point in the ignited regime or a high-Q operating point in a subignited case taking into account density and beta limits and stabilizing the reactor performance against changes in confinement.