With the TEXTOR tokamak being shut down at the end of 2013, the plasma physics division at Forschungszentrum Jülich enhances its research on Plasma-Wall Interactions with materials science. A dedicated linear plasma device, JULE-PSI, is under construction and will start operation in 2015.

Christian Linsmeier and Ulrich Samm in the PSI-2 laboratory (Photo: H. Reimer, Forschungszentrum Jülich)

Christian Linsmeier and Ulrich Samm in the PSI-2 laboratory (Photo: H. Reimer, Forschungszentrum Jülich)

“We are currently the only group in Europe – if not in the world – that combines expertise in linear facilities for Plasma-Wall Interaction studies and materials research,“ says material scientist Prof. Christian Linsmeier. In March 2013, Linsmeier was appointed director of the plasma physics division of FZ Jülich’s Institute for Energy and Climate research (IEK). He leads it in conjunction with director Prof. Ulrich Samm. Before that, Linsmeier headed the research group for plasma-facing materials and components at IPP Garching. He sees new opportunities for fusion material science at FZ Jülich, pointing out synergies with the IEK’s divisions for Microstructure and Properties of Materials and for Materials Synthesis and Processing.
As the global fusion community begins conceptual work on demonstration power plants, it has become important, not only to investigate the physical processes that take place between the hot plasma and the reactor wall, but also to develop new materials capable of withstanding the conditions in those plants. FZ Jülich’s new linear plasma device JULE-PSI is designed to deliver plasma conditions which are relevant for future fusion power stations (see Fusion Europe 1/2011). It will be located inside a hot cell, allowing investigations to be carried out with neutron activated materials or materials containing beryllium. Construction of the hot cell will commence in 2014.

Three main concepts

Fusion materials research at FZ Jülich addresses three main concepts. Firsty, tungsten composites which might help solve the problem that tungsten, the preferred wall material for fusion reactors walls, turns brittle under the anticipated operational conditions. The development of these materials started at IPP Garching and will be continued in collaboration. Secondly, self-passivating alloys which is an additional project that will be conducted in conjunction with IPP. These alloys provide an additional level of safety. For instance, if the cooling system fails, a self-heating alloy would develop a protecting oxide layer and thus prevent radioactive isotopes from escaping from the hot wall. Thirdly, barrier layers for tritium which prevent the element from diffusing through the first wall into the structural steels. The fusion fuel tritium is elaborately produced in the reactor wall and any loss has to be prevented. Moreover, tritium would activate the wall structure and possibly contaminate the cooling fluid.

A unique centre of competence

JULE-PSI is one of four linear devices for Plasma-Wall Interaction studies in Europe. VISION I at SCKCEN, Belgium, operates with tritium plasmas at moderate power. MAGNUM PSI at DIFFER in The Netherlands, features high enough particle and heat fluxes and densities to study divertor materials under realistic conditions. JULE-PSI is able to investigate hazardous or activated materials in a high-power tritium plasma. Finally, PSI-2 – a similar experiment to JULE-PSI, but outside the hot cell – is already operational at FZ Jülich. Together these institutes form the Trilateral Euregio Cluster (TEC), a unique centre of competence for Plasma-Wall Interaction studies addressing the needs of the fusion device after ITER.