Improving heat flux calculations for the non-axisymmetric loads on plasma facing components in Wendelstein 7-X

This paper presents the new thermographic inversion code DELVER (Divertor Energy Load Versatile EstimatoR). Its task is to calculate the heat flux distribution on plasma-facing components from the evolution of surface temperature derived from infrared camera measurements. For operational campaign 2 of Wendelstein 7-X, water-cooled high-heat flux divertors made of layers of different materials have been installed into the plasma vessel. The previously employed explicit thermographic inversion code, THEODOR, was deemed insufficient to model these accurately due to the missing capability of defining multiple material layers. This motivated the development of DELVER, which improves upon explicit THEODOR in further aspects by handling 1D, 2D, and 3D modeling with flexible boundary conditions, an implicit solver, arbitrary functional temperature dependency of the orthotropic thermal properties of the materials, and a non-equidistant orthogonal calculation grid. The two codes are being compared using a simple analytical model, the finite element solver ANSYS®, and finally, experimental heat flux calculated from the calorimetry and heat fluxes calculated from infrared measurements. In all test cases, good agreement between DELVER simulations and expected results is achieved.