A control-oriented model for breakdown and burn-through in TCV and its application

摘要

The need for tokamak start-up modelling and control The pulsed nature of experimental tokamak fusion devices implies the hot plasma needs to be formed over and over again. This justifies better understanding and optimization of this particular transient phase, such that a higher reliability and reproducibility can be achieved. From a physical point of view, plasma start-up in tokamaks can be divided into four different regimes, indicated in Figure 1: first, a neutral gas is injected and a favorable magnetic topology is created inside the vacuum vessel, having a large region with a purely toroidal magnetic field. Then the gas is ionized via collisions with electrons, which are accelerated and confined by an electric and magnetic field respectively. After a successful breakdown, the newly formed plasma is contaminated by impurity particles originating from the tokamak inner wall, which radiate away a large portion of the applied heating power. However, upon ionization, these impurities radiate less intensely, calling for sufficient heating of the plasma. When this is achieved, the plasma can be further heated and fueled, such that the fusion-relevant conditions are reached.