Plasma shape control assessment for JT-60SA using the CREATE tools

Abstract

This paper deals with the plasma shape control problem in JT-60SA. An assessment of the plasma shape control performance is presented, aimed at the definition of an optimal set of gaps to be controlled. Indeed, JT-60SA represents a relevant benchmark to further validate this control approach given the high beta regimes that are envisaged during its operation. Moreover, such regimes represent a challenge from the plasma magnetic control perspective. The control approach considered for the assessment is based on the eXtreme Shape Controller (XSC), since such an approach permits to control, in a least mean square sense, a number of shape descriptors that is larger than the number of poloidal field coils. Considering that the design of the XSC is model-based, the CREATE linear model for the plasma-circuit response has been used for the design. In the presented analysis, the capability of tracking different plasma shapes, as well as the one of rejecting disturbances has been considered. The result of this analysis suggests that a set of about 20 gaps equally spaced along the plasma boundary permits to control the shape with a steady-state root-mean square error of less than 1 cm during the flattop of JT-60SA Scenario 2, in the presence of a set of relevant disturbances.