Tokamak active laser pyrometry for tungsten deposited layer characterisation

In modern fusion reactors, the erosion of plasma facing surface results in layers deposition on tokamak “cold” surfaces. To provide efficient operation of tokamaks, it is essential to characterise the deposited layer with high tritium content. In situ rapid surface characterisation without reactor components disassembly is required. Active laser pyrometry together with a repetition rate Nd–YAG laser (1 Hz–1 kHz repetition rate frequency) applied for surface heating can be used to characterise some thermo-physical properties (thermal capacity, thermal contact, and conductivity) of a micrometric layer. The pyrometer system was developed and applied to characterise some properties of a W-layer (140 μm) on a CFC-substrate. The numerical code developed for 3-D simulation of LH of a surface with the deposited layer was applied to simulate the experimental heating temperatures. The experimental and simulation results were compared. W-layer characterisation was performed by fitting the experimental and theoretical heating temperatures.