Laser Ablation Properties of JT-60 Re-deposited Carbon Layers

Laser ablation properties of re-deposited carbon layers on a JT-60 divertor tile have been investigated for various laser intensities using a ps-laser system in order to develop a tritium removal method from DT fusion reactor using laser-induced desorption (LID). Desorbed gases and erosion depth were measured by a quadrupole mass spectrometer and an optical microscope, respectively. Erosion depth revealed that ablation of carbon occurred at laser intensity I L >9×10 9 W/cm 2 . It was found that retained hydrogen desorbed mainly as H 2 and C 2 H 2 accompanying minor contribution of other hydrocarbon molecules, but much less as H 2 O molecules by the laser ablation. It was also found that most of the retained hydrogen on the re-deposited layer was removed by the laser ablation. It appeared that for the higher I L , hydrogen can be removed more quickly with less production of hydrocarbons. These results suggest that LID has a superior nature as a tritium removal method.