Nonlinear burn control in fusion reactors

Control of plasma density and temperature magnitudes, as well as their profiles, are among the most fundamental problems in fusion reactors. Unfortunately, the economy of fusion reactors often requires the reactor to operate under conditions in which the rate of thermonuclear reaction increases as the plasma temperature rises. In this thermally unstable zone, an active control system is necessary to stabilize the thermonuclear reaction. Existing efforts use control techniques for linear models. In this work, a zero-dimensional nonlinear model involving approximate conservation equations for the energy and the densities of the species was used to synthesize a nonlinear feedback controller for stabilizing the burn condition of a fusion reactor. The controller makes use simultaneously of the modulation of auxiliary power, the modulation of fueling rate and the controlled injection of impurities as actuators. A computer simulation study was performed to show the capability of the controller and compare it with previous linear controllers.