Modeling of hydrogen implantation into graphite

Abstract

A new theoretical framework has been developed which is applicable to the implantation and ion-induced release of hydrogen isotopes in graphite. It provides a physical basis and a refinement of the predictions of the simple model of local saturation and mixing. The model treats the trapping at defects and a local release of trapped atoms by nuclear knock-on. Ion deposition and damage functions are taken from trim simulations. The detrapped atoms may become retrapped or recombine to molecules, which then are transported to the surface by fast molecular diffusion, and subsequently released. By the choice of suitable rate constants in the model calculations, different experimental findings for the implantation and high-fluence self-reemission of deuterons in graphite may be explained consistently. Examples cover the saturation as a function of temperature and energy, depth profiles, gas reemission, thermal desorption, and effects of predamage.

Dynamic Monte-Carlo modeling of hydrogen isotope reactive–diffusive transport in porous graphite

“…Many detailed macroscopic models have been proposed to study hydrogen isotope inventory and transport in porous graphite [1][2][3][4] and hydrocarbon formation and transport in graphite [8]. These models use rate constants for transport from experiments [9][10][11][12][13]7], some of which still need theoretical explanations. There exists many microscopic models [14][15][16][17] using MD with either empirical potentials or density functional theory and they give an insight into the microscopic mechanisms studied in graphite.…”

Electron spectroscopy measurements on hydrogen implanted graphite and comparison to amorphous hydrogenated carbon films (a-C:H)

“…Electron spectroscopy measurements are very well suited for these investigations, because of their high surface sensitivity. Note that the penetration depth of the hydrogen ions is in the range of about 50 nm, at an energy of 3 keV [5]. In addition, it allows in situ ultrahigh vacuum measurements to be performed.…”

“…In addition, a close resemblance in the electronic structure of hydrogen bombarded graphite and amorphous hydrogenated carbon films (a-C :H) is shown which suggests the modification of pristine graphite to an amorphous network [1] of mostly tetrahedrally bonded carbon atoms by hydrogen implantation. 79.20-m, 79.60-i, 73.60-n Graphite is an interesting material in the field of plasma fusion research because of its outstanding physical properties as a first wall material for limiters in fusion reactors (Tokamak) [2][3][4][5]. In particular, one requires a low-Zmaterial with a low vapor pressure.…”

Hydrogen release and retention from porous graphite

“…Many detailed macroscopic models have been proposed to study hydrogen inventory and transport in porous graphite [1,2,4,8] and hydrocarbon formation and transport in graphite [9]. These models use rate constants for transport from experiments [10][11][12][13][14]5], some of which still need theoretical explanations. There exist many microscopic models [15][16][17][18] using MD with either empirical potentials or density functional theory and they give insight into the microscopic mechanisms studied in graphite.…”