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Plasma Wall Interaction in TEXTOR

Nearly 20% of the thermal power of a fusion reactor has to be transferred from the hot plasma through the wall components of the burn chamber. This has to be achieved without overheating and excessive erosion of the plasma facing materials, without degrading the thermonuclear burn process by impurities released from the walls, and without burying too much tritium. Moreover, the helium ashes produced by the fusion processes have to be removed from the plasma with sufficient efficiency but without lowering the quality of thermal isolation of the fusion plasma.

The objective of the Implementing Agreement on Plasma Wall Interaction in TEXTOR is to study these processes, to evaluate their relative importance and to develop methods for their control. This includes the development of novel specific diagnostics and of methods to condition the wall, to structure the wall and the magnetic field and to influence the transport features of the confined plasma. The Implementing Agreement is based on a particularly strong and valuable collaboration between Canada, EURATOM, Japan and the United States. In the course of the world-wide research on fusion power, heat removal, particle exhaust and the other objectives of this Agreement coupled with plasma confinement as a whole, have emerged as priority tasks for developing a long pulse reactor. They require a variety of approaches (e.g. materials, divertors, limiters) to be developed, tested and evaluated.

Medium-sized machines like TEXTOR have the particular mission of exploring new methods and concepts before transferring them to the large devices of reactor grade performance. The research programme is highly relevant for next generation machines, both on the tokamak development path (ITER) and the stellarator path (Wendelstein 7-X), and more generally for a stationary fusion reactor. Work under the Agreement has contributed to the solution of problems concerning the interaction between the plasma and the reactor wall; including controlled heat transfer onto and through the wall, impurities released from the wall, retention of the nuclear fuel (tritium) in the wall and removal of the helium ashes produced by the fusion process. It has enabled the partners to make use of the TEXTOR facility to progress technology development and enabled the transfer of knowledge from TEXTOR to other research facilities, contributing to the total development process.

Boronisation techniques pioneered through this Agreement are now applied world-wide as a method to reduce oxygen impurities in tokamak and stellarator plasmas. Edge radiation cooling developed through TEXTOR is regarded as a promising technique to alleviate the heat transfer problems of ITER and other fusion devices. Their application lead to a new regime of very good and stationary confinement, the so-called Radiation Improved Mode. Mechanisms to remove Helium (in particular by a toroidal pumplimiter), have been successfully demonstrated. Low Z and high Z materials like carbon and tungsten have been tested and evaluated. A series of useful edge diagnostics has been developed and applied. The recent implementation of the "Dynamic Ergodic Divertor" (DED) and the new powerful ECR heating system opens further possibilities to study and influence the particle and energy transport in the plasma boundary layer by "magnetic edge layer vortexing" and local deposition of heating powers up to 1 MW.Studies of erosion and deposition of wall materials, tritium retention and recycling, as well as tests of advanced wall materials and concepts, optimisation of radiative scenarios, exploitation of operational limits linked to plasma-edge instabilities, particle removal and transport studies related to the magnetic topology at the boundary, can be significantly furthered within the Agreement by utilisation of these novel experimental means.

Signatories : Japan | United States | European Atomic Energy Community (EURATOM) |
For more information: Under development

Current Projects (Annexes)

Plasma Wall Interaction in TEXTOR
Evaluate the importance of impurities build-up process and wall damage, and search for appropriate first wall materials, structures and conditions