Plasma boundary reconstruction in ISTTOK using magnetic diagnostic data
Résumé
Plasma boundary reconstruction is one of the main tools to provide a reliable control and tokamak performance. We explore the feasibility for the ISTTOK tokamak of a reconstruction method based on calculated vacuum magnetic flux map and plasma intersection with the wall. We show that via square wave input response curves and pre-processing of the poloidal field coil currents, it is possible to build for ISTTOK a simple scaling model for the effective equilibrium magnetic fields, and perform plasma boundary reconstruction using the algorithm VacTH. This algorithm, included in the NICE numerical code suite, relies on the decomposition of the poloidal flux in toroidal harmonics. The reconstructed plasma boundary is shown for a given discharge and its shape and position are shown to evolve consistently with the typical timescale evolution of ISTTOK discharges. This provides an opportunity of using this plasma boundary reconstruction method as a diagnostic tool for ISTTOK. Finally the need for further work is discussed regarding a more accurate quantification of the effects of the eddy currents in the copper shell present in ISTTOK, as well as alternative plasma boundary characterization methods in order to validate the results obtained here.