A convenient analytical parametrization of a tokamak plasma last closed flux surface for use in shape and discharge design

Abstract An analytical parametrization of the last closed flux surface of a tokamak plasma is proposed, based on a reduced list of global shape parameters that are conveniently defined. This parametrization can reproduce a variety of shapes, from limited to diverted, lower and upper single null, double null, and diverted negative triangularity plasmas. The choice of the parameters is well suited to be used for easy shape and more generally discharge design, in view of fitting the coil currents that are required to form the desired shape.