The Adaptive Toroidal Equilibrium (ATEQ) code and its applications*

The Adaptive Toroidal Equilibrium (ATEQ) code is developed for axisymmetric MHD equilibria. A decomposition with independent solutions is employed in the radial direction and the Fourier decomposition is used in the poloidal direction. The independent solutions are then obtained using an adaptive shooting scheme together with the multi-region matching technique. Using the backward substitution method to the Grad-Shafranov equation, its accuracy is checked and compared with existing equilibrium codes. It shows that the adaptive numerical scheme by ATEQ improves substantially the accuracy of equilibrium calculations, especially in the presence of separatrix. Comparison with existing codes will be detailed and especially how the ATEQ code improves the EFIT equilibrium results will be given. The necessity for better equilibrium solutions will also be discussed for the physics assessment of ITER or other existing devices.