Tritium recovery from co-deposited layers using 193-nm laser

Shu, Wataru; Kawakubo, Yukio*; Nishi, Masataka

Recovery of tritium from co-deposited layers formed in TFTR deuterium-tritium plasma operations was investigated by the use of an ArF excimer laser operating at the wavelength of 193 nm. At the laser energy density of 0.1 J/cm, a transient spike of tritium release rate was observed at initial irradiation. Hydrogen isotopes were released in the forms of hydrogen isotope molecules during the laser irradiation in vacuum, suggesting tritium can be recovered readily from the released gases. In a second experiment, hydrogen (tritium) recovery from the co-deposited layers on JT-60 tiles was investigated by laser ablation with focused beam of the excimer laser. The removal rate of the co-deposited layers was low when the laser energy density was smaller than the ablation threshold (1.0 J/cm), but reached to 1.1 m/pulse at the laser energy density of 7.6 J/cm. The temperature on the surface during the irradiation was measured on the basis of Planck's law of radiation, and the maximum temperature at the laser energy density of 0.5 J/cm decreased from 3570 K at the initial irradiation to 2550 K at 1000th pulse of the irradiation.