HYDROGEN ABSORPTION BEHAVIOR INTO BORON FILMS BY GLOW-DISCHARGES IN HYDROGEN AND HELIUM

Hydrogen absorption behavior into boron films deposited on graphite an d stainless steel (SS) has been studied. Hydrogen absorption into a H- depleted boron film was investigated during a hydrogen glow discharge with pressure drop measured by a diaphragm gauge. It was found that, a fter strong but short time absorption at initial phase, hydrogen atoms were slowly (a few percents of injected H atoms) but continuously abs orbed without saturation up to 3 h, which was not observed with SS lin er without boron coating. Hydrogen atoms were not only desorbed but al so implanted into the film during a helium glow discharge and thus, hy drogen atoms were accumulated in the film when H, and He discharges we re repeated alternately. These accumulation effects enhanced by ions f rom the glow discharge were investigated quantitatively and the effect of bombarding ion species (H+ or He+) was discussed. Depth profile of H atoms was measured by elastic recoil detection (ERD). The density o f only near surface region was increased when the hydrogen atoms were injected. Longer time exposure to H, discharge resulted in increase in surface density and shift of the peak position to deeper into the fil m. These results were explained by diffusion of H atoms due to ion imp act into the films with keeping its saturation level if we consider re solution of ERD method of 25 nm. From the results, applicability of bo ron film as protection layer of tritium permeation is discussed.