Speaker
Rudolf Neu
(Plasmarand und Wand)
Description
Since 2014 ASDEX Upgrade (AUG) is using bulk tungsten tiles at the outer divertor strike-point. In two experimental campaigns more than 2000 plasma discharges with up to 10 s duration and 100 MJ plasma heating were successfully conducted, without impairment by the W tiles. However, an inspection after the campaigns revealed that a large number of tiles suffered from deep cracking, mostly attributed to brittle fracture. This could be overcome by alloying with rhenium which increases the ductility considerably or by the use of W fibre reinforcement which increases the toughness. However, these solutions either suffer from high costs or are not yet ready for routine use.
An alternative solution – at least for non-nuclear fusion devices – could be the use of W heavy alloys as they are produced commercially by several companies. They consist of up to 97% W and Ni/Fe (or Ni/Cu) admixtures, they are readily machinable and considerably cheaper than pure tungsten. Their major drawbacks in view of the application in fusion experiments are the rather low melting temperature (~1500 °C) of the Ni/Fe binder phase and their magnetic properties. In a first step W heavy alloys from two manufacturers were subjected to screening tests and cyclic loading in the high heat flux test facility GLADIS with up to 20 MW/m² and surface temperatures of up to 2000 °C, showing no macroscopic failure. SEM investigations show a segregation of Ni and Fe at the top surface after the thermal overloading, but no signs of micro-cracking. The longterm behaviour under plasma and electromagnetic load and the influence of the Ni/Fe preferential sputtering and the magnetic properties will be investigated with the AUG divertor manipulator. Moreover, the mechanical properties of the virgin and loaded material will be compared to those of tungsten used in the AUG divertor.
Co-authors
Albrecht Herrmann
(Experimentelle Plasmaphysik 1, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
Hans Maier
(Plasmarand und Wand, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
Henri Greuner
(Plasmarand und Wand, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
Irene Zammuto
(Experimentelle Plasmaphysik 1, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
Martin Balden
(Plasmarand und Wand, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
Rudolf Neu
(Plasmarand und Wand, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany;Fakultät für Maschinenwesen, Technische Universität München, Boltzmannstr.15, 85748 Garching, Germany)
Team ASDEX Upgrade
(Experimentelle Plasmaphysik 1, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
Till Hoschen
(Plasmarand und Wand, MPI für Plasmaphysik, Boltzmannstr.2, 85748 Garching, Germany)
