Plasma-Wall Interaction - A Key Issue in Progress Towards Fusion Power Plants
Generating energy from fusion requires a plasma with a temperature of 100 million degrees. Strong magnetic fields are used to protect the wall of a fusion device and although this reduces the interaction of the plasma with the walls, they are still exposed to considerable loads that are inherently unavoidable. For this reason, fusion research has focused on plasma-wall interaction right from the outset – and today, particularly at Jülich, it is a central issue.
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Plasma-Wall Interaction in Linear Plasma Devices
The interaction between the plasma and the wall materials in a fusion reactor is a key factor determining the lifetime of the wall components and thus the overall cost-effectiveness of the facility. Both the ITER experiment currently under construction and DEMO, the first demonstration reactor, will bring about particular challenges.
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Material tests under very high loads
The emphasis of the research in the high temperature materials laboratory (HML) is put on experiments for the characterization of materials and components for the First Wall and Divertor of the actually built or planned fusion devices ITER and DEMO, respectively.More: Material tests under very high loads …
Plasma-facing Materials
The "first wall" is the name given to the surface of the inner wall of a fusion reactor. This wall is in direct contact with the plasmy and is thus directly affected by the plasma and its constituents. This means that very high temperatures - up to 1,000 °C - can occur. Moreover, the magnetic confinement of the ions in the plasma is not perfect, with the result that the surface of the first wall is also continuously bombarded by ions from the plasma.
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Theoretical and Computational Fusion Edge Plasma Science
The development of future fusion reactors such as ITER and DEMO, whether as tokamaks or stellarators, requires accurate predictions regarding the stability of plasma operation and the intensity of plasma-wall interaction. An important objective of theoretical fusion physics at Jülich is to mathematically describe the plasma-wall system so effectively that reliable calculations and predictions can be made. However, this problem is characterized by a high degree of complexity as a result of the interplay between a variety of electromagnetic, fluid dynamics, kinetic, atomic physics, chemical, and surface physics processes that, moreover, take place on very different temporal and spatial scales.
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Wendelstein 7-X
The world's largest stellarator,Wendelstein 7-X,is running at theMax-Planck-Institute for Plasma Physicsin Greifswald. With respect to the magnetic confinement of fusion plasmas, the stellarator principle is a promising alternative to the tokamak, as it enables stationary plasma operation and thus opens up new possibilities for investigating reactor-relevant physics issues. Yet Wendelstein 7-X also presents new challenges connected with complex geometry, on the one hand, and, on the other, with the necessity of maintaining continuous operation of the wall components, plasma observation systems (diagnostics), control system, and data acquisition.More: Wendelstein 7-X …
ITER
The large-scale fusion experiment ITER (Latin for "the way") is currently under construction in Cadarache in the south of France as part of an international cooperation and is scheduled for completion by 2020. ITER aims to demonstrate the physical and technological feasibility of fusion energy on a power-plant scale and thus pave the way for the commercial exploitation of fusion. By means of the fusion of heavy hydrogen (deuterium) and super-heavy hydrogen (tritium), up to 500 million watts of fusion power will be produced at ITER for the first time ever.
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JET ITER-like Wall
Forschungszentrum Jülich designed and constructed a divertor, which is part of the new first wall in the leading fusion experiment, JET - the "ITER-like wall". This wall consists of beryllium and tungsten, while the divertor is made entirely of tungsten, the material with the highest melting point. This metal, which only melts at a temperature of 3,455 °C, will also be used at a later stage in ITER. Jülich scientists are currently testing their promising design at JET.
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DEMO
The large scale fusion experiment ITER (Latin for "the way") ) is currently under construction in Cadarache in the south of France. ITER is the world’s first fusion reactor, and its aim is to achieve a positive energy balance in the fusion of deuterium and tritium. However, the length of the plasma pulses produced will only be between a few minutes and one hour. In addition, the expected fusion power produced with a power gain of Q = 10 is still too low to be used for net electricity generation. The ITER experiment will nevertheless develop and demonstrate solutions on a practical scale to all fundamental physical and technical issues on the path towards fusion energy. Net electricity generation will then be the task of a subsequent device – the demonstration reactor DEMO. In comparison to ITER, DEMO will be somewhat larger, have higher fusion power and power gain, and thus be capable of feeding several hundred million watts of electrical energy into the grid. Another of DEMO’s important goals is to achieve higher availability than ITER, which necessitates longer plasma pulses on the one hand and a longer lifetime for all components on the other.
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TEXTOR
Was the largest fusion experiment at Jülich for 30 years until 2013. The mission of it was to expose the inner wall with heat and particle loads at intensities relevant for ITER and future reactors already today. TEXTOR was a test bed for wall materials of fusion reactors. Furthermore, a Dynamic Ergodic Divertor (DED) allowed for efficient control of instabilities in the fusion plasma.More: TEXTOR …
Scientific Publications
Every year, we publish well over a hundred articles on fusion research in scientific journals and books.
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