Modelling of dusty plasmas: A+M data needs
- FOM Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands)
- Plasmant (Dept. of Chemistry), University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium)
Processing plasmas often produce clusters, ranging in size from a few nanometer up to micrometers. Due to their negative charge, clusters are confined by the sheath electric fields until their mass enables gravity to pull them out of the discharge. Examples are discharges in SiH4 or C2H2. Although there is agreement on the global aspects of the chemistry, details on many processes are lacking. This concerns attachment of electrons to large molecules, restructuring leading to a reduction of the hydrogen content, and the interaction between large negative ions and (excited) molecules, radicals, and positive ions of the parent gas. Results from a one-dimensional model for a radio-frequency discharge in SiH4/H2 will be used to illustrate the consequences of various assumptions regarding these basic steps in the chemistry.For discharges in mixtures containing hydrocarbons the incorporation of C2 groups in polycyclic aromatic hydrocarbons has been proposed as an additional mechanism for dust formation. This is the main process adopted in astrophysics. Also in Tokamaks the formation of carbonaceous dust is observed, caused mostly by the erosion of carbon containing divertor tiles and redeposited layers on plasma facing components. In case of detached operation the plasma in the divertor will be similar to that of a processing discharge, favoring homogeneous processes. In ITER this will be accompanied by hydrogen ion fluxes up to 1024 m-2s-1 and power fluxes up to 10 MWm-2, leading to evaporation of wall material. Here we will discuss the chemistry in these situations (processing discharges and divertors), indicating open questions regarding cluster formation.
- OSTI ID:
- 20718962
- Journal Information:
- AIP Conference Proceedings, Vol. 771, Issue 1; Conference: ITC14: 14. international Toki conference on plasma physics and controlled Nuclear Fusion; ICAMDATA2004: 4. international conference on atomic and molecular data and their applications, Toki (Japan), 5-8 Oct 2004; Other Information: DOI: 10.1063/1.1944699; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANIONS
CARBON
CATIONS
DIVERTORS
DUSTS
ELECTRIC FIELDS
EVAPORATION
FIRST WALL
HIGH-FREQUENCY DISCHARGES
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN IONS
ITER TOKAMAK
MOLECULES
ONE-DIMENSIONAL CALCULATIONS
PLASMA
PLASMA SIMULATION
POLYCYCLIC AROMATIC HYDROCARBONS
RADIOWAVE RADIATION
SILICON COMPOUNDS