???aural:Bildanfang???ASDEX Upgrade at the Max Planck Institute of Plasma Physics in Garching being prepared for operation of ITER. © Max Planck Institute for Plasma Physics (IPP)/Volker Steger???aural:Bildende???

The ASDEX (Axial Symmetric Divertor Experiment) Upgrade fusion device at the Max Planck Institute for Plasma Physics (IPP) in Garching is being prepared for operation of the ITER international experimental reactor. ITER, now being built at Cadarache, France, aims to demonstrate that it is possible to derive energy from fusion of atomic nuclei - just as the sun does. This requires that the fuel, an ionised hydrogen gas called plasma, is confined in a magnetic field cage and heated to ignition temperatures of over 100 million degrees Celsius. One of the challenges is to achieve tolerable interaction between the plasma vessel and the hot plasma suspended in it.

IPP favours a vessel wall made of tungsten, as it is the metal with the highest melting point. Two years of experimentation in ASDEX Upgrade have confirmed the advantages afforded by the tungsten wall. It could be shown that clean plasmas can be obtained - almost too clean. While impurities in the plasma centre have to be avoided since they cool the plasma and thus reduce the fusion yield, this cooling is very useful at the plasma edge. Thus, nitrogen impurities were deliberately injected into the edge of the plasma. This nitrogen cooling reduced the wall load to a tolerable level. Nevertheless, the plasmas afforded a high degree of purity at the core. Their energy content was one of the highest ever obtained in the device.

This eminently satisfies all ITER requirements - a highly promising result, because in terms of important comparative parameters, ASDEX Upgrade comes closer to ITER than any other fusion device.

Contact: Isabella Milch, Max Planck Institute for Plasma Physics  oeffentlichkeitsarbeit@ipp.mpg.de

More information: www.ipp.mpg.de