Modelling of dust grain formation in a low-temperature plasma reactor used for simulating parasitic discharges expected under tokamak divertor domes

Abstract

The presence of nanostructured dust particles has been reported in thermonuclear fusion reactors with carbon plasma-facing components. These particles contribute to tritium retention and pollution of the edge plasma. Understanding the way these particles can grow in the plasma phase is necessary for designing engineering solutions that avoid or at least limit their formation. As a first step towards this goal, this paper presents a numerical study of the formation of dust in a simple model laboratory electrical discharge: a dc discharge generated in argon with a graphite electrode. The aim here is to investigate whether carbon sputtering through ion and fast neutral bombardment of the cathode and subsequent molecular growth of carbon clusters and particle nucleation and development can explain dust formation in this model discharge. Results show that field reversal effects and negative cluster formation and trapping can fully explain dust formation in such a dc discharge.

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

“…On the other hand, the plasma potential profile allows negative ions to be confined in the plasma beam and ion-driven chemistry might promote the particle growth. 56,57 …”

Nanoparticle formation and dusty plasma effects in DC sputtering discharge with graphite cathode

“…For this purpose, we substantially improved the model that was previously developed to investigate the molecular growth of carbon clusters and the onset of particle formation [8,9] in order to achieve a self-consistent description of clustering, aerosol dynamic and discharge equilibrium. The paper includes five sections.…”

Carbon Nanoparticle/Hydrogenated Amorphous Carbon Composite Thin Films Formed in ECR Plasma

“…The second behavior observed in the FTIR spectra appears when subtracting the baseline (Figure 6b): two groups of large absorption bands appear linked to the structure of powders inside the diffusion plasma – the first one, attributed to sp 1 RCCH species (790, 1 260 and 2 070cm −1 ) and the second one (1 020 and 1 570cm −1 ) corresponding to substituted sp 2 aromatic rings. These two kinds of species are frequently observed in powders formed in plasma processes15 or combustion,16 where the main mechanisms for powder growth are polymerization of acetylenic group and formation of aromatic rings by hydrogen abstraction and carbon addition. If we focus on the main peak at 1 020 cm −1 , it is possible to determine the carbon volume fraction of powders by fitting the absorbance using a Lorentzian:17 where ν 0 and Δ ν 1/2 represents respectively the absorption frequency and the bandwidth.…”