Real-time model-based wall heat flux estimation for ITER

A real-time (RT) first wall (FW) heat load control system will be required at a very early stage of ITER plasma operations. A Matlab/Simulink architecture containing a 2D, control oriented model, based on RT equilibrium reconstruction has been successfully implemented for the ITER Plasma Control System (PCS). Integration of the real 3D nature of the ITER PFCs into the algorithm is performed by offline determination of the heat load distribution on a full 3D poloidal sector using a new magnetic field line tracing utility, SMITER, permitting import and appropriate meshing of CAD descriptions of the FW geometry. Weighting factors are then derived with which to correct the peak heat fluxes obtained from the 2D model for implementation into the heat flux control algorithm. A detailed study of the ramp-up phase in a limiter configuration has been performed using the DINA code to generate magnetic equilibria and including a plasma current scaled, double exponential radial profile of parallel heat flux. The approach proposed for ITER has been experimentally demonstrated and benchmarked against off-line measurements from infra-red (IR) camera diagnostics for both limiter and diverted plasma configurations on the TCV tokamak.