An Extended Kalman Filter approach for tokamak plasma equilibrium reconstruction

For tokamak operations, several plasma quantities need to be known in real time with a given level of accuracy. Some of these quantities cannot be measured directly and reliably, hence, estimation algorithms are needed. In particular, equilibrium reconstruction based on magnetic measurements is fundamental for real time control to provide plasma shape and possibly current profiles distribution. This paper deals with the development and testing of an Extended Kalman Filter for magnetic equilibrium reconstruction, with the objective of reconstructing plasma shape, plasma parameters and passive currents in the tokamak structure. The novelty of the proposed approach is to use a full nonlinear free-boundary equilibrium code (CREATE-NL+), including eddy currents, to obtain the a-priori estimate. The effectiveness of the proposed approach is demonstrated on two segments of an ITER 15MA DT Scenario: an early ramp-up segment and an HL transition. Results are compared with those obtained with other approaches.