The mathematical concepts of the necessary conditions for tokamak plasma shape identification are discussed. A method that uses only the derived necessary condition is proposed. This method is based on the boundary integral equations governing the vacuum region around the plasma, using only the measured values of either the magnetic fluxes or the magnetic flux intensities. The application to JT-60U and ITER plasmas shows that this method can be used to identify various plasmas with low to high ellipticities, with the necessary precision, when an adequate number of magnetic sensors is provided. The proposed method is also applicable to real-time control and visualization
Three-dimensional Cauchy-condition surface method to identify the shape of the last closed magnetic surface in the Large Helical Device