• Energy Research

Using liquid metals confined in capillary porous structures (CPSs) as a plasma-facing component (PFC) could prolong the lifetime of the divertor in the high heat flux area. However, the high atomic number of tin (Sn) limits its acceptable fraction in the main plasma. Therefore, a crucial step in developing this concept is to test it in a tokamak environment, particularly in the diverted plasma region, e.g. ASDEX Upgrade (AUG). In this paper, the design of liquid tin module (LTM) is explained, and the testing in the high heat flux device GLADIS before its use in AUG is presented. The LTM was additively manufactured using selective laser melting, consisting of a 1.5mm porous layer tungsten (W) directly attached to a solid W bulk. The LTM has a plasma-facing area of 16×40mm2 and was filled with 1.54g of Sn. In GLADIS, the module was exposed to power loads between 2 and 8MWm−2 for 1 up to 10s, first unfilled and later filled with Sn. The surface temperature was monitored with infrared imaging and pyrometry. The thermal response was used to compare with simulations in Ansys Mechanical, enabling a determination of the module’s effective thermal properties. Sn droplets could be observed on the infrared camera, until a surface temperature of about a 1000°C was reached. The enhanced wetting of tin on the plasma-facing surface, which was observed by a visible camera, suggests that there is a conditioning of the surface, possibly due to the removal of impurities and oxides. Subsequent examinations of the adjacent tile revealed minor Sn leakages emanating from the module’s edge. Furthermore, the module showed no indication of mechanical failure. Therefore, these results indicated that the LTM qualifies for the heat fluxes expected in ASDEX Upgrade.

Abstract The JET 2019–2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major neutral beam injection upgrade providing record power in 2019–2020, and tested the technical and procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle (α) physics in the coming D–T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed shattered pellet injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design and operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D–T benefited from the highest D–D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER.

Nuclear materials and energy 15, 214-219 (2018). doi:10.1016/j.nme.2018.05.001 Published by Elsevier, Amsterdam [u.a.]

The preferred plasma-facing material in present-day and future magnetic confinement thermonuclear fusion devices is tungsten. This material is mainly chosen because of its high threshold energy for sputtering by hydrogen isotopes as well as its low retention of tritium within the material. From an engineering point of view, however, tungsten is a challenging material to work with as it is an inherently hard and brittle metal. In this respect, established fabrication technologies for tungsten and tungsten based materials are a limiting factor directly affecting the design of plasma-facing components. Against this background, additive manufacturing technologies could prove very beneficial with regard to plasma-facing component applications as they offer flexibilities beyond the possibilities that conventional manufacturing methods offer. Within the present contribution, we report on recent results regarding the additive manufacturing of tungsten by means of powder-bed based selective laser beam melting. In more detail, investigations on pure tungsten manufactured by using elevated substrate preheating temperatures up to 1000 ∘C are described. Keywords: Additive manufacturing, Refractory metal, Tungsten, Laser beam melting, Plasma-facing material

The design and manufacture of highly heat loaded plasma-facing components (PFCs) represents a major challenge for the realisation of thermonuclear magnetic confinement fusion. The performance of such PFCs is essentially related to the properties of the materials that are used for their design. Currently, tungsten fibre-reinforced metal matrix composites (MMCs) are regarded as promising advanced materials for PFC applications. In this respect, tungsten fibre-reinforced tungsten is being investigated as an advanced pseudo-ductile plasma-facing material while tungsten fibre-reinforced copper is being developed as an advanced heat sink material. The essential ingredients for the abovementioned MMCs are the fibrous reinforcements which are commercially available drawn tungsten fibres.An important aspect regarding the development of the abovementioned MMCs is the effect of the composite material manufacturing process on the properties of these high-strength reinforcements. During composite material manufacturing experiments it has been found that the mechanical properties of the used W fibres can be deteriorated significantly already at process temperatures of approximately 1200 °C.Against this background, dedicated investigations have been conducted on drawn tungsten fibre samples. In more detail, single fibre tensile tests, microstructural investigations as well as chemical composition analyses have been conducted. All in all, the performed investigations indicate that impurities incorporated into the tungsten fibre material are the underlying reason for the observed deterioration of the mechanical properties. Keywords: tungsten, fibre-reinforced, copper, metal matrix composite, plasma-facing component

Nuclear materials and energy 37, 101514 - (2023). doi:10.1016/j.nme.2023.101514 Published by Elsevier, Amsterdam [u.a.]