Characterization of time varying thermophysical property of a surface layer: Numerical feasibility for JET tokamak tiles

The present paper deals with the thermal characterization of the Surface Carbon Layer (SCL) usually poorly attached to the Plasma Facing Component (PFC) inside the nuclear fusion machines (Tokamak). A nonlinear unsteady calculation combined with the Conjugate Gradient Method (CGM) and the adjoint state is achieved in order to characterize in situ the time variation of the thermal resistance Rth of a surface layer. A numerical feasibility is presented with a realistic virtual experiment design. The accuracy of the method is examined by using simulated exact and inexact infrared measurements obtained on the SCL surface. The advantages of applying the CGM with the adjoint state in the present study, are that no prior information is needed on the time variation and the initial guess of the unknown thermal resistance.