Layer removal in gaps by laser process

Abstract The laser ablation technique had been already shown to be well suited to clean the top surface of the Toroidal Pumped Limiter of Tore Supra. The next phase was to apply this technique to the deposits observed in the gaps. This paper focuses on the characterization of gap deposits and the optimization of the laser cleaning process for this application. In general most of the deposits are located inside the gap within the first mm. In the toroidal direction most of the deposits are located on the low field side with thicknesses reaching up to 610 μm, while in the poloidal direction deposits thicknesses up to 450 μm are observed on both sides. The influence of the laser angle has been investigated; an angle of 45° is recommended in the toroidal direction while a perpendicular beam is adopted in the poloidal direction. This study concludes that gap cleaning induces significant additional time for castellated surfaces.