Plasma-wall interaction in fusion devices encompasses a wide variety of processes. On a short timescale these include deposition of energetic plasma particles (primarily hydrogen and helium) into the surface, physical and chemical sputtering of surface material into the plasma, and reflection and desorption of particles from the surface. On a longer timescale the processes include diffusion of hydrogen and helium in the wall and changes in surface composition, morphology and material microstructure due to plasma bombardment and (in a reactor) neutron irradiation. Together these processes are extremely important in determining the plasma performance, the lifetime of plasma-facing components, trapping and retention of the tritium fusion fuel in the wall, and ultimately the feasibility of fusion power production.
The gap between what is known about plasma-material interaction and what is needed to design a fusion reactor is most severe for the effects of radiation damage on hydrogen retention properties of plasma-facing materials. Computations are particularly important for this problem, because experiments cannot fully simulate the radiation conditions in a fusion device. Appropriate computational materials tools range from statistical or otherwise averaged (binary collision approximation, kinetic Monte Carlo) and mechanical (molecular dynamics) models to semiempirical (tight binding) density functional theory codes and the best possible “first principles” electronic structure codes for inhomogeneous materials. Any of these codes has its own needs for fundamental data, which are in many cases obtained by parameterization of results of other calculations.
In order to discuss these issues the Abdus Salam International Centre for Theoretical Physics (ICTP) and the International Atomic Energy Agency (IAEA) jointly organized the Conference on Models and Data for Plasma-Material Interaction in Fusion Devices, held 3–7 November 2014 at ICTP in Trieste, Italy. The conference brought together researchers from fusion energy science and materials science in order to review advances in computational studies of plasma-material interaction processes and evolution of material microstructure in fusion devices, including effects of radiation damage and with special interest in hydrogen (tritium) trapping and transport in wall material. The meeting was successful enough that it was followed by the 2015 International Workshop on Models and Data for Plasma-Material Interaction, 25–27 May 2015 in Marseille, France, while the 2016 International workshop on Models and Data for Plasma-Material Interaction in Fusion Devices is planned to be held 22–24 June 2016 in Loughborough, UK (in conjunction with the COSIRES meeting).
Following the event at ICTP it was agreed with the Editors of Journal of Nuclear Materials to solicit articles for the present theme issue, in which theoretical and computational work is emphasized that is traceable to fundamental electronic structure theory. Contributions have come from participants in the ICTP-IAEA meeting and from other researchers. Specific topics of interest for the theme issue include the following.
• Direct uses of “ab initio” and semi-empirical quantum mechanical codes for study of materials microstructure and trapping and transport of hydrogen and helium in fusion wall materials.
• Optimization of parameters in semi-empirical codes and parameterization of results of electronic structure calculations in the form of interaction potentials and transition rates for classical models.
• Molecular Dynamics and Kinetic Monte Carlo studies of plasma-material interaction, radiation damage processes and material and surface evolution.
• Multi-method and multi-scale simulations; acceleration approaches.
• Uncertainty estimation and uncertainty propagation from quantum mechanical calculations through interaction potentials to outputs of longer time-scale calculations.
• Parameterization of material microstructure and its effect on mobility and trapping of hydrogen and helium in fusion wall materials.
• Simulation and interpretation of diagnostics of material microstructure, radiation damage, hydrogen and helium in fusion materials and plasma-material interaction.
All the submitted manuscripts have gone through regular refereeing according to the standards of Journal of Nuclear Materials and finally 12 articles have been accepted. The guest editors express their thanks to all the contributors for their work and for submitting it to this issue.
For more detail on each article, and to download the full-text PDFs, please see the links below:
New interatomic potentials for studying the behavior of noble gas atoms in tungsten
Fen Zhou, Jingzhong Fang, Huiqiu Deng, Jianglong Liu, Shifang Xiao, Xiaolin Shu, Fei Gao, Wangyu Hu
Positron annihilation lifetime measurement and X-ray analysis on 120 MeV Au+7 irradiated polycrystalline tungsten
Charu Lata Dube, Pawan Kumar Kulriya, Dhanadeep Dutta, Pradeep K. Pujari, Yashashri Patil, Mayur Mehta, Priyanka Patel, Samir S. Khirwadkar
Sputtering of mixed materials of beryllium and tungsten by hydrogen and helium
A. Mutzke, G. Bandelow, R. Schneider
Migration of rhenium and osmium interstitials in tungsten
Tomoaki Suzudo, Masatake Yamaguchi, Akira Hasegawa
Macroscopic rate equation modeling of trapping/detrapping of hydrogen isotopes in tungsten materials
E.A. Hodille, X. Bonnin, R. Bisson, T. Angot, C.S. Becquart, J.M. Layet, C. Grisolia
Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature
R. Bisson, S. Markelj, O. Mourey, F. Ghiorghiu, K. Achkasov, J.-M. Layet, P. Roubin, G. Cartry, C. Grisolia, T. Angot
Kinetic Monte Carlo simulation on influence of vacancy on hydrogen diffusivity in tungsten
Takuji Oda, Deqiong Zhu, Yoshiyuki Watanabe
A first-principles investigation of interstitial defects in dilute tungsten alloys
Leili Gharaee, Paul Erhart
Statistical study of defects caused by primary knock-on atoms in fcc Cu and bcc W using molecular dynamics
M. Warrier, U. Bhardwaj, H. Hemani, R. Schneider, A. Mutzke, M.C. Valsakumar
He–He and He–metal interactions in transition metals from first-principles
Pengbo Zhang, Tingting Zou, Jijun Zhao
The influence of nitrogen co-deposition in mixed layers on deuterium retention and thermal desorption
Anže Založnik, Sabina Markelj, Iztok Cadež, Primož Pelicon, Primož Vavpetic, Corneliu Porosnicu, Cristian P. Lungu
Damage at a tungsten surface induced by impacts of self-atoms
Yong Wu, Predrag Krstic, Fu Yang Zhou, Fred Meyer