Fuel removal from bumper limiter tiles by using a pulsed excimer laser

Samples of a limiter tile from the TEXTOR tokamak were investigated by scanning electron microscopy and nuclear reaction analysis both before and after laser heating. SEM images showed spheres and thin flakes covering the surface which are the areas modified by plasma particles striking under grazing angles. Due to roughness of the surface there are shadowed regions between the ‘flakes’. Laser pulses did not lead to expected common ablation of the surface. Features that looked like ‘melting’ of thin surface layers were rather observed. The initial deuterium content in the surface layer of tiles was of the order of 1018 D atoms per cm2. After the laser light impact the content decreased with 60–70%; by reducing the deposited power by a factor four, the deuterium content was decreased by 40–50%. We make the interpretation that we approach a threshold of the laser detritiation method in fusion devices.