Current Profile Control for the Development of Consistent Discharges in DIII-D

W.P. Wehner, J.E. Barton, M.D. Boyer, E. Schuster, M.L. Walker, D.A. Humphreys, J.R. Ferron, T.C. Luce, B.G. Penaflor and R.D. Johnson

54th IEEE Conference on Decision and Control

Osaka, Japan, December 15-18, 2015

Abstract

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.