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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 IL≥9x109 W/cm2. It was found that retained hydrogen desorbed mainly as H2 and C2H2 accompanying minor contribution of other hydrocarbon molecules, but much less as H2O 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 IL, 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.