Hydrogen retention of carbon dust prepared by arc discharge and electron beam irradiation

Tritium retention of carbon dust co-deposited with fuel hydrogen is so large that it is required to evaluate the tritium inventory for estimating potential hazards of next step fusion reactors such as International Thermonuclear Experimental Reactor (ITER). In the present work, the authors prepared carbon dust samples by two methods. One was deuterium (D2) arc discharge with carbon electrodes to simulate co-deposition of carbon atoms with hydrogen atoms. The other was electron beam irradiation to carbon fiber composite (CFC) target in hydrogen gas to simulate disruptions. The dependence of retained hydrogen amount on hydrogen gas pressure and substrate temperature was investigated. The surface morphology and the crystal structure were also examined. In the case of D2 arc discharge, the concentration of retained deuterium was increased with the deuterium gas pressure, but did not depend on substrate temperature from 573 to 723 K. Under the anticipated ITER divertor condition, namely deuterium gas pressure and substrate temperature were less than 1 Pa and 573 K, the deuterium concentration was 0.2 in the atomic ratio, D/C. In the case of electron beam irradiation, the amount of retained hydrogen was the same as the background level.