Special Session (Nuclear Fusion):

Title:         Atomic and molecular data and modeling of tungsten plasma -facing materials for fusion energy
Authors:      D. KATO, H. A. Sakaue, I. Murakami, N. Nakamura, T. Muroga
Abstract:     Safety and fueling efficiency are key issues to realize fusion power plants on the earth. Tungsten is selected as divertor materials for ITER (International Thermonuclear Experimental Reactor), because less tritium retention and erosion are expected. However, radiation damages by D-T neutrons and high heat fluxes to the divertor will enhance tritium retention and erosion of the tungsten materials. Modeling and data on tritium retention in damaged tungsten are advanced by means of Density Functional Theory (DFT). Multiple hydrogen trapping in single mono-vacancies forming VHn complexes were predicted from first-principals [1]. Hydrogen de-trapping rates from the large complexes (n=3) exhibit the double peak feature as a function of temperature [2] that have experimentally been observed in deuterium thermal desorption spectra of D+- irradiated tungsten specimens. DFT molecular statics analysis reveals that the VHn complexes can supress vacancy and self-interstitial-atom (SIA) annihilation and trap the adjacent SIA [3]. Tungsten sputtered into core plasmas is highly ionized and will cause large radiation power loss of the core plasmas. Spectral data of line emission from tungsten ions can be used to investigate tungsten ion distributions in the core plasmas. A compact electron-beam-ion-trap (CoBIT) [4, 5] was originally developed to measure precisely the emission line of Wq+ ions of q = 10-30 colliding with a mono-energetic electron beam. Spectral modeling using collisional-radiative models based on complex kinetic processes of the tungsten ions in plasmas is also carried out [6].

Keywords:   Tungsten, Radiation damage, Tritium retention, Density functional theory, Highly charged ion, Electron beam ion trap, Collisional-Radiative model
Pages:          013-013

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