An integral approach to plasma shape control

A novel representation of the plasma boundary is presented, which employs a B-spline approach to describe the deformation of the plasma surface in an integral way, without resorting to the local properties of the shape as in the gap technique. The evolution of such a curve on the poloidal plane corresponds to that of the plasma shape and a spline controller is designed to counteract disturbances and regulate the plasma shape error during the discharge. The comparison with a gap controller highlights the accuracy in the control capability of the spline controller and its completeness, in the sense that the control of the spline curve implies (but is not implied by) the control of the gaps.