Papers by Author: Jochen Linke

Abstract: Tungsten and tungsten alloys are promising metals as protective materials for the armour in future fusion reactors. These metals exhibit the highest melting point, superior thermo-mechanical properties, low erosion and moderate neutron activation properties. The main drawback is their intrinsic brittleness at room temperature and their low recrystallization temperature. During thermal shock events in ITER, tungsten materials will exhibit various crack formations and failure mechanisms. The extensive heat loads on the surface of the material will create high thermal stresses, huge temperature rises and therefore large strain rates in the subsurface layers. This paper deals with the flow properties combining both temperature and strain rate effects of a lanthanum oxide dispersion strengthened tungsten material and the influence of grain orientation on its ductility. Promising results were obtained using a yield strength model based on a thermally-activated slip process that rationalizes the data.

Abstract: The technical design solution for the future thermonuclear fusion reactor, ITER, must guarantee a reasonable lifetime from a safety and economical point of view. Carbon fibre reinforced carbon (CFC) is envisaged as a corrective material solution for the strike point area of ITER divertor due to its high thermal shock resistance necessary to withstand excessive heat loads during transient thermal loads; in particular plasma disruptions that can deposit energy densities of several ten MJm-2 with a typical timescale in the order of milliseconds. In this work, as potential alternative to CFCs new finely dispersed TiC-doped isotropic graphites with high thermal conductivity and mechanical strength, manufactured using synthetic mesophase pitch “AR” as raw material, have been evaluated under typical disruption conditions using an energetic electron beam at the JUDITH facility.

Abstract: To evaluate the performance of plasma facing materials (PFM) and components for future thermonuclear fusion devices under the expected operation conditions, an in-depth material characterization and extensive high heat flux simulation tests are performed routinely in electron beam test facilities. These experiments cover both, thermal fatigue tests with power densities up to approx. 20 MWm-2 and thermal shock loads with deposited energy densities of several MJm-2. In addition, irradiation experiments have been performed in material test reactors to investigate the neutron induced material degradation.