Active contours approach for plasma boundary reconstruction

In the current generation of tokamak devices, fusion performance is related to plasma geometric characteristics as elongation and triangularity. Shape diagnostics and control systems are, therefore, essential to plasma operations. It follows that the quality of a tokamak control system depends on the availability of fast and reliable measurements of plasma position and shape. For this purpose, classic reconstruction and control algorithms that have been applied to existing machines refer to the position of a discrete set of points (gaps) around the outermost flux surface [Proc. 11th Symp. Fusion Technol. 2 (1980) 1033; Fusion Technol. 1 (1994) 731]. The paper presents an attempt of producing an integral, more than pointwise description of the plasma boundary using modern techniques, derived from the active vision field. It provides an intuitive and elegant tool for plasma boundary representation and dynamic reconstruction, while widening the point of view over plasma shape diagnostics and control systems. A comparison with the reconstruction code currently available at JET will be presented.