Current profile control for the development of consistent discharges in DIII-D

The number of tokamak discharges required to carry out meaningful experiments can be significantly reduced by current profile control in the early startup phase. The tokamak is a plasma-confinement device, suitable for confining plasma at the requisite high temperature necessary for initiating fusion. It is currently the most promising device for realizing sustained fusion power generation at a commercial grade level, though it is still in the experimental stage. Presently, difficult to achieve plasma conditions, such as the shape of the plasma current profile, are achieved in a trial and error fashion, which can be a lengthy, wasteful process. In this work we make use of model-based control techniques such as optimal feedforward control via nonlinear programming and linearized feedback control to obtain a target current profile at a specified time in low-confinement-mode (L-mode) discharges. The effectiveness of the controller is demonstrated experimentally.