Studies on Re-emission Behavior of Hydrogen Isotopes from Wall Materials by Means of Ion Beam Analysis Techniques

点击翻译按钮获取中文摘要

Goal of this project is to clarify the elementary processes in the re-emission of hydrogen isotopes from wall materials and to establish the model describing their dynamic behavior in the wall materials for prediction and evaluation of hydrogen isotopes recycling during He discharge and main discharged.In 1990 and 1991, we have performed following tasks for graphite materials concerning with this project.1) Depth profiles of hydrogen isotopes in graphite during and after implantation at flux of 6x10^<15>/cm^2s at room temperature have been measured by means of the elastic recoil detection technique. It has been found from comparison between both depth profiles that dynamic retention of hydrogens in graphite is so small not to be detected.2) The concentration decays of hydrogen isotopes in graphite, implanted with 3 keV H^+_ or D^+_ ion beams up to saturation, induced by 1.5 MeV He^+ ion bombardment have been measured at temperatures from RT to 250ﾟC. It has been found that the decay of … More H concentration is faster than of D concentration. This isotopic difference is shown to be explained in terms of isotopic difference in the ion-induced detrapping cross-section and the ratio of the rate constants of local molecular recombination between an activated hydrogen and a trapped one and retrapping.3) The concentration decays of hydrogen isotopes in graphite, implanted with 3 keV H^+_ or D^+_ ion beams up to concentration, induced by isothernal annealings have been measured at temperatures from 450 to 600ﾟC It has been also found that the decay of H concentration is faster than that of D concentration. This isotopic difference is also shown to be explained in terms of istopic difference in the rate constants of thermal detrapping, retrapping and local molecular recombination between activated hydrogens.4) Using the re-rmission profiles obtained in the re-emission experiment, it is shown that the thermal desorption spectrum on hydrogen isotopes implanted into graphite is theoretically predicted using the mass balance equations describing their dynamic behaviors. It is found that the calculated thermal desorption spectrum of hydrogen molecule agrees well with the experimental ones when the physical parameters obtained in the isothermal re-emission experiment are used. Less