Articolo in rivista, 2013, ENG, 10.1088/0029-5515/53/12/123002

Migration of tungsten dust in tokamaks; role of dust-wall collisions

S. Ratynskaia (1; L. Vignitchouk (1; P. Tolias (1; I. Bykov (2; H. Bergsåker (2; A. Litnovsky (3; N. den Harder (4; E. Lazzaro (5

1) Division of Space and Plasma Physics, Association EURATOM-VR, Royal Institute of Technology KTH, Sweden 2) Division of Fusion Plasma Physics, Association EURATOM-VR, Royal Institute of Technology KTH, Sweden 3) Institut fur Energieforschung-Plasmaphysik, Forschungszentrum J ¨ ulich, Association ¨ EURATOM-FZ Julich, Germany ¨ 4 FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, The Netherlands 5) Istituto di Fisica del Plasma-CNR, Association EURATOM-ENEA-CNR, Milano, Italy

The modelling of a controlled tungsten dust injection experiment in TEXTOR by the dust dynamics code MIGRAINe is reported. The code, in addition to the standard dust-plasma interaction processes, also encompasses major mechanical aspects of dust-surface collisions. The use of analytical expressions for the restitution coefficients as functions of the dust radius and impact velocity allows us to account for the sticking and rebound phenomena that define which parts of the dust size distribution can migrate efficiently. The experiment provided unambiguous evidence of long-distance dust migration; artificially introduced tungsten dust particles were collected 120o toroidally away from the injection point, but also a selectivity in the permissible size of transported grains was observed. The main experimental results are reproduced by modelling.

Nuclear fusion (Online) 53 , pp. 642–646

Keywords

Dust transport, wall reflections, tungsten

CNR authors

Lazzaro Enzo

CNR institutes

IFP – Istituto di fisica del plasma "Piero Caldirola"