IOP PUBLISHING

PLASMA PHYSICS AND CONTROLLED FUSION

Plasma Phys. Control. Fusion 52 (2010) 124007 (9pp)

doi:10.1088/0741-3335/52/12/124007

Similarities and differences between dust produced in laboratory plasmas and in the MAST and Tore Supra tokamaks C Arnas1 , C Martin1 , P Roubin1 , B P´egouri´e2 , G De Temmerman3,5 , K Hassouni4 , A Michau4 , G Lombardi4 and X Bonnin4 1 2 3 4

Laboratoire PIIM, UMR 6633 CNRS-Universit´e de Provence, Marseille, France Association Euratom CEA Cadarache, CEA/DSM/IRFM, St Paul Lez Durance, France EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, UK LIMHP, UPR 1311 CNRS, Universit´e Paris 13, Villetaneuse, France

Received 15 June 2010, in final form 22 July 2010 Published 15 November 2010 Online at stacks.iop.org/PPCF/52/124007 Abstract It is shown that among the dust produced from plasma–surface interaction in tokamaks, nanoparticles growing in gas phase can be produced in large quantities in MAST and Tore Supra, two tokamaks of carbon-based plasmafacing components. Laboratory plasma experiments and models are also presented showing that when carbonaceous species are present, complex chemical pathways which depend strongly on plasma conditions lead to various molecular precursors. Despite this fact, the final solid particles produced in the laboratory plasmas and tokamaks considered here, present similarities giving information on their growth and transport in the plasma. (Some figures in this article are in colour only in the electronic version)

1. Introduction In laboratory low pressure plasmas, dust particles are produced by various mechanisms. The flaking of deposited layers on the device surface during plasma enhanced chemical vapor deposition process is a source of micro-dust as well as the etching of wafers by plasma– surface interaction. These sources of contamination are generally minimized by improved chamber cleaning. The plasma also has the property to generate particulates from complex volume chemistry. They are produced by discharges in reactive gases where specific reactions lead to growing macromolecules/clusters up to the nucleation mechanism, i.e. the formation of nanoparticles by homogeneous growth. On the other hand, sputtered surfaces by plasma fluxes also supply atoms or clusters which can nucleate [1, 2]. 5

Current address: FOM Institute for Plasma Physics, Nieuwegein, The Netherlands.

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