Establishment of Modeling of Hydrogen Isotopes Recycling in Plasma Facing Material for Control of the D-T Burning Experiments

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Goal of this project is to clarify the elementary processes in the retention and reemission of hydrogen isotopes for plasma facing materials and to establish the model describing their dynamic transport in the materials for prediction and evaluation of hydrogen recycling rates during H^+ and D^+ dual irradiations.In 1993 and 1994, we have following tasks for graphite materials concerning this project.1) The mass balance equations describing the transport of hydrogen isotopes in graphite during single hydrogen ion irradiation have been proposed and the rate constants of the elementary process involved are reviewed. The mass balance quations for dial H^+ and D^+ irradiations have been proposed.2) The energy dependence of the depth profiles and the peak concentrations of hydrogen refained in graphite by implantation with H_2^+ ion beams at energies 0.2-5.0keV has been measured by means of the elastic recoil detector (ERD) technique. The steady state depth profile and peak concentrations a … More re found to be well explained in terms of the solution of the mass balance equations proposed.3) The MeV He^+ ion-induced re-emission of hydrogen isotopes (H,D) from graphite implanted with 5 KeV H_2^+ or D_2^+ ion beams upto saturation at room temperature were measured by means of the ERD technique and the He^+ ion induced detrapping crosssection and the ratio of the local molecular recombination rate to the trapping rate were defermined. It is found that the isotope ratio of the latter values for H to D is about 2 which was reasonably well explained in terms of the diffusion-limited reaction model.4) The retention curves of H and D in graphite irradiated simultaneously withH_2^+ and D_2^+ ion beams at room temperature were measured under the condition that both projected range are the same. The isotope ration of the saturation concentrations of D to H was found to be 1.7 which was excellently well explained by the solution of the mass balance equations for the H^+ and D^+ dual irradiations proposed and the rate constants of elementary processes based on the diffusion-limites reaction model. Less