Modeling of H/D isotope-exchange in crystalline beryllium
A reaction-diffusion model with surface occupation dependent desorption [D. Matveev et al., Nucl. Instr. Meth. B 430 (2018) 23–30] has been updated to handle multiple hydrogen species to simulate hydrogen/deuterium isotope-exchange experiments performed on polycrystalline beryllium samples under ult...
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doaj-988d4ea366bf492eafaf9969cf381e762020-11-25T01:29:10ZengElsevierNuclear Materials and Energy2352-17912019-08-0120Modeling of H/D isotope-exchange in crystalline berylliumD. Matveev0P. Hansen1T. Dittmar2H.R. Koslowski3Ch. Linsmeier4Corresponding author.; Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, GermanyForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, GermanyForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, GermanyForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, GermanyForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, GermanyA reaction-diffusion model with surface occupation dependent desorption [D. Matveev et al., Nucl. Instr. Meth. B 430 (2018) 23–30] has been updated to handle multiple hydrogen species to simulate hydrogen/deuterium isotope-exchange experiments performed on polycrystalline beryllium samples under ultra-high vacuum laboratory conditions. In the experiments subsequent exposures of a sample to hydrogen and deuterium ion beams in direct and reverse implantation order were followed by thermal desorption spectroscopy measurements under a constant heating rate of 0.7 K/s. The recorded signals of masses 2 to 4 (H2, HD and D2) indicate that the second implanted isotope dominates clearly the low temperature release stage ( ≈ 450 K), while both isotopes show a comparable contribution to the high temperature desorption stage ( ≈ 700 K) with only minor effect of the implantation order attributed to a slightly deeper penetration of deuterium compared to hydrogen. Simulations of the implantation and subsequent thermal desorption of hydrogen isotopes are performed to assess the atomic processes behind the isotope-exchange. Simulations were performed under the assumption that the low temperature release stage is attributed to hydrogen/deuterium atoms retained on effective open surfaces (e.g. interconnected porosity) represented in the simulations by a surface with an effective surface area exceeding the nominal exposed surface area by a factor up to 100. Kinetic de-trapping from vacancies with multiple trapping levels and enhanced desorption at surface coverages close to saturation are addressed in the model as possible mechanisms promoting the isotope-exchange. Simulation results suggest the applicability of the model to describe isotope-exchange processes in crystalline beryllium and give a qualitative explanation of the observed experimental facts. Keywords: Beryllium, Isotope-exchange, Hydrogen retention, Reaction-diffusion, TDShttp://www.sciencedirect.com/science/article/pii/S2352179118302655 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
D. Matveev P. Hansen T. Dittmar H.R. Koslowski Ch. Linsmeier |
spellingShingle |
D. Matveev P. Hansen T. Dittmar H.R. Koslowski Ch. Linsmeier Modeling of H/D isotope-exchange in crystalline beryllium Nuclear Materials and Energy |
author_facet |
D. Matveev P. Hansen T. Dittmar H.R. Koslowski Ch. Linsmeier |
author_sort |
D. Matveev |
title |
Modeling of H/D isotope-exchange in crystalline beryllium |
title_short |
Modeling of H/D isotope-exchange in crystalline beryllium |
title_full |
Modeling of H/D isotope-exchange in crystalline beryllium |
title_fullStr |
Modeling of H/D isotope-exchange in crystalline beryllium |
title_full_unstemmed |
Modeling of H/D isotope-exchange in crystalline beryllium |
title_sort |
modeling of h/d isotope-exchange in crystalline beryllium |
publisher |
Elsevier |
series |
Nuclear Materials and Energy |
issn |
2352-1791 |
publishDate |
2019-08-01 |
description |
A reaction-diffusion model with surface occupation dependent desorption [D. Matveev et al., Nucl. Instr. Meth. B 430 (2018) 23–30] has been updated to handle multiple hydrogen species to simulate hydrogen/deuterium isotope-exchange experiments performed on polycrystalline beryllium samples under ultra-high vacuum laboratory conditions. In the experiments subsequent exposures of a sample to hydrogen and deuterium ion beams in direct and reverse implantation order were followed by thermal desorption spectroscopy measurements under a constant heating rate of 0.7 K/s. The recorded signals of masses 2 to 4 (H2, HD and D2) indicate that the second implanted isotope dominates clearly the low temperature release stage ( ≈ 450 K), while both isotopes show a comparable contribution to the high temperature desorption stage ( ≈ 700 K) with only minor effect of the implantation order attributed to a slightly deeper penetration of deuterium compared to hydrogen. Simulations of the implantation and subsequent thermal desorption of hydrogen isotopes are performed to assess the atomic processes behind the isotope-exchange. Simulations were performed under the assumption that the low temperature release stage is attributed to hydrogen/deuterium atoms retained on effective open surfaces (e.g. interconnected porosity) represented in the simulations by a surface with an effective surface area exceeding the nominal exposed surface area by a factor up to 100. Kinetic de-trapping from vacancies with multiple trapping levels and enhanced desorption at surface coverages close to saturation are addressed in the model as possible mechanisms promoting the isotope-exchange. Simulation results suggest the applicability of the model to describe isotope-exchange processes in crystalline beryllium and give a qualitative explanation of the observed experimental facts. Keywords: Beryllium, Isotope-exchange, Hydrogen retention, Reaction-diffusion, TDS |
url |
http://www.sciencedirect.com/science/article/pii/S2352179118302655 |
work_keys_str_mv |
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