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P: Fachverband Plasmaphysik

P 12: Plasma Surface Interaction II - Helmholtz Graduate School IV

P 12.6: Vortrag

Dienstag, 19. März 2019, 18:10–18:35, HS 20

Induction-heating based gas loading of tungsten samples for determination of protium and deuterium diffusion parameters in tungsten — •Georg Holzner^1,2, Thomas Schwarz-Selinger¹, and Udo von Toussaint¹ — ¹Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748 Garching — ²Technische Universität München, Boltzmannstraße 15, 85748 Garching

For future fusion power plants, it will be important to predict fuel retention and transport, i.e. deuterium and tritium, in the first wall, which will probably be made of tungsten. Retention and transport modelling depend on a proper description of diffusion. For the most basic hydrogen isotope protium, the generally accepted experimental diffusion parameters stem from Frauenfelder from the late 60s. Since then, measured values scatter by several orders of magnitude, for which presumably trapping effects are the reason. Recent DFT-results question the Frauenfelder value. Furthermore, for deuterium in tungsten the amount of available data is even more scarce.

For this reason, the diffusion of protium and deuterium in tungsten was measured as well as their solubilities. This has been performed at temperatures between 1800 and 2600 K, because at these temperatures trapping effects can be neglected and pure diffusion is the governing transport effect. An ultra high vacuum (UHV)/gas loading experiment was designed and built. The measured diffusion equation for protium deviates considerably from Frauenfelder's value, the diffusion prefactor for deuterium does not follow classical predictions.