Control-oriented modeling of the plasma particle density in tokamaks and application to real-time density profile reconstruction

A model-based approach to real-time reconstruction of the particle density profile in tokamak plasmas is presented, based on a dynamic state estimator. Traditionally, the density profile is reconstructed in real-time by solving an ill-conditioned inversion problem using a measurement at a single point in time. This approach is sensitive to diagnostics errors and failure. The inclusion of a dynamic model in a real-time estimation algorithm allows for reliable reconstruction despite diagnostic errors. Predictive simulations show that the model can reproduce the density evolution of discharges on TCV and ASDEX-Upgrade after tuning of a few parameters. Offline reconstructions using experimental data from TCV show accurate estimation of the density profile and show examples of fault detection of interferometry signals.