X. Bonnin
Iter Research, Science and Operations, Graduate Student
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ABSTRACT Nanostructured dust particles are often found in thermonuclear fusion reactors with carbon plasma-facing components [1]. Parasitic plasmas in remote locations of fusion devices may contribute to the formation of this dust.... more
ABSTRACT Nanostructured dust particles are often found in thermonuclear fusion reactors with carbon plasma-facing components [1]. Parasitic plasmas in remote locations of fusion devices may contribute to the formation of this dust. Particle formation in these conditions is investigated here using a simple laboratory DC electrical discharge. We make use of a numerical model to analyze the formation of dust through cathode sputtering and subsequent molecular growth.The model developed for this study includes three modules. The first one describes the DC discharge in a dust-free plasma with a Monte-Carlo simulation combined with an analytical discharge model. In the second module we perform the computation of growth and transport of carbon clusters and particles in the discharge column [2]. The largest molecular edifice (C15) is assumed to give rise to spontaneous nucleation of solid particles. The third plasma module solves for the total dust density, average mass and average charge.
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The importance of correct description of plasma-wall interaction processes in edge plasma transport codes is well-known: creation of impurities by different sputtering processes, recycling coefficients for energy, particles and momentum,... more
The importance of correct description of plasma-wall interaction processes in edge plasma transport codes is well-known: creation of impurities by different sputtering processes, recycling coefficients for energy, particles and momentum, pumping properties of walls are examples of crucial phenomena determining the divertor characteristics and edge solution. To improve the B2-solps5. 0 edge modelling package a new PSI (plasma-surface interaction) package was developed [1] and introduced, taking into account especially ...
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1) Max-Planck-Institut für Plasmaphysik, EURATOM Association, 85748 Garching, Germany 2) Max-Planck-Institut für Plasmaphysik, EURATOM Association, 17491 Greifswald, Germany 3) Courant Institute, NYU, New York, USA 4) Institut für... more
1) Max-Planck-Institut für Plasmaphysik, EURATOM Association, 85748 Garching, Germany 2) Max-Planck-Institut für Plasmaphysik, EURATOM Association, 17491 Greifswald, Germany 3) Courant Institute, NYU, New York, USA 4) Institut für Allgemeine Physik, TU Wien, Austria, Association EURATOM-OEAW 5) St. Petersburg State Technical University, St. Petersburg, Russia 6) ITER JCT, Garching, Germany 7) Düsseldorf University, Düsseldorf, Germany ... E-mail contact of main author: David.Coster@ipp.mpg.de ... Abstract. The continuing development of the ...
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The formation of carbon nanoparticles in low pressure magnetized H2/CH4 and H2/C2H2 plasmas is investigated using infrared quantum cascade laser absorption, mass spectrometry, and electrostatic probe measurements. Results showed that dust... more
The formation of carbon nanoparticles in low pressure magnetized H2/CH4 and H2/C2H2 plasmas is investigated using infrared quantum cascade laser absorption, mass spectrometry, and electrostatic probe measurements. Results showed that dust formation is correlated to the presence of a significant amount of large positively charged hydrocarbon ions. Large negative ions or neutral hydrocarbon were not observed. These results, along with a qualitative comparison of diffusion and reaction characteristic, suggest that a positive ion may contribute to the growth of nanoparticles in hydrocarbon magnetized plasmas.
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The issue of tungsten contamination of the main plasma is an important one for ITER. In order to clarify some of the issues, SOLPS modelling has been performed for ITER with a species mix of D+T+He+Be+Ne+W: D+T as the primary hydrogenic... more
The issue of tungsten contamination of the main plasma is an important one for ITER. In order to clarify some of the issues, SOLPS modelling has been performed for ITER with a species mix of D+T+He+Be+Ne+W: D+T as the primary hydrogenic species, He produced by fusion reactions, Be and W produced by sputtering from the main wall and targets, and Ne as a control parameter to increase the power radiated.
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Coupled fluid plasma and kinetic Monte Carlo neutrals simulations in a linear configuration are reported. The configuration mimics the tokamak divertor plasma channel contacting a target surface with nearby wall. We calculate the... more
Coupled fluid plasma and kinetic Monte Carlo neutrals simulations in a linear configuration are reported. The configuration mimics the tokamak divertor plasma channel contacting a target surface with nearby wall. We calculate the parameters of the source plasmas, 3-5m from the target, required to produce high recycling target plasmas recently simulated for ITER. It is shown that the source plasma needs to deliver heat fluxes of 10-20MW/m2, ion fluxes of 1023/m2/s, densities of 2-6x1019/m3, and electron and ion temperatures of 15-30eV over a plasma radius of 5-6cm. The neutral H and H2 fluxes to the vessel wall are calculated to be comparable to those measured in the divertor regions of today s tokamaks. These results identify some design features for a prospective plasma material test station and the research required for this plasma source.
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In cold, high-density plasma regions such as MARFEs and detached divertor plasmas, the photon mean free paths of the Lyman series emissions can be smaller than the emitting region size. This optical thickness phenomenon greatly... more
In cold, high-density plasma regions such as MARFEs and detached divertor plasmas, the photon mean free paths of the Lyman series emissions can be smaller than the emitting region size. This optical thickness phenomenon greatly complicates the analysis of spectroscopic data and creates a non-local energy transport channel. In this poster, we describe an effort to model the radiation transport using the CRETIN code. We benchmark our results against experimental data. We proceed in order of increasing complexity. First, we assess the importance of optical thickness in the regime of interest (Te << 1 eV, Ne ~ few times 10^21 m-3) and compare the CRETIN model to a simpler escape-probability formalism and assess the impact of geometry on the simulation. Second, we develop a 1-D model of the midplane MARFEs obtained in Alcator C-Mod. Third, we extend this model to a two-dimensional description. Last, we present some results concerning the divertor region in detached operation.
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ABSTRACT A modeling study of carbon clusters and dust particles formation through carbon graphite sputtering in argon DC discharges is presented. The model combines the description of plasma discharge kinetics, molecular growth and... more
ABSTRACT A modeling study of carbon clusters and dust particles formation through carbon graphite sputtering in argon DC discharges is presented. The model combines the description of plasma discharge kinetics, molecular growth and transport of carbon clusters and aerosol dynamics for dust particles. Results show that field reversal is a key effect that ensures trapping and growth of negatively charged molecular carbon clusters, which are the precursors for dust particles. The model enables prediction of the space–time distributions of carbon clusters density as well as dust particle density, average charge and average diameter. Results especially show that dust particles and carbon clusters exhibit a pronounced density maximum in the vicinity of the field reversal position. A parametric study is presented in order to analyze the model sensitivity to some key parameters used in the physical model.
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Research Interests: Geology, Computer Science, Physics, Kinetics, Monte Carlo, and 15 moreNumerical Simulation, Mathematical Sciences, Physical sciences, Methane, Finite Volume, Finite Difference, Length scale, Finite Difference Method, Interaction effect, Low Temperature, Kinetic Monte Carlo, Molecular Dynamic Simulation, Monte Carlo Method, Electron Cyclotron Resonance Heating, and Molecular dynamic
mixed materials, layers and coatings, bundled charge states, and hydrogen inventory X. Bonnin, D.P. Coster, M. Warrier, A. Rai, R. Schneider 1 CNRS-LIMHP, Universite Paris 13, Villetaneuse, France 2 Max-Planck-Institut fur Plasmaphysik,... more
mixed materials, layers and coatings, bundled charge states, and hydrogen inventory X. Bonnin, D.P. Coster, M. Warrier, A. Rai, R. Schneider 1 CNRS-LIMHP, Universite Paris 13, Villetaneuse, France 2 Max-Planck-Institut fur Plasmaphysik, EURATOM Association, Garching-bei-Munchen, Germany 3 Institute for Plasma Research, Bhat, Gandhinagar, Gujarat, India 4 Max-Planck-Institut fur Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Greifswald, Germany
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Abstract. The simulation of massive gas injection, done with the 2D transport code SOLPS, allows to calculate the temporal evolution of the total (free plus bound) electron density profile. The calculations show that a volume averaged... more
Abstract. The simulation of massive gas injection, done with the 2D transport code SOLPS, allows to calculate the temporal evolution of the total (free plus bound) electron density profile. The calculations show that a volume averaged total electron density, of the order of magnitude of the so-called “Rosenbluth density”, can been reached in ASDEX Upgrade after the injection of neon with a fast valve in disruption mitigation experiments. This result supports the possibility of suppressing runaway electrons generated during the current ...
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Research Interests: Materials Engineering, Chemistry, Nuclear Materials, Tokamak, Detachment, and 3 moreHelium, Jet, and Divertor
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We report on electromagnetic simulations of an industrial thin film deposition process for hydrogenated amorphous carbon using microwave plasmas.This process is designed to deposit a barrier coating on the inside of a PET bottle. This... more
We report on electromagnetic simulations of an industrial thin film deposition process for hydrogenated amorphous carbon using microwave plasmas.This process is designed to deposit a barrier coating on the inside of a PET bottle. This process relies on a resonant cavity coupled to a lateral waveguide. This cavity excites an acetylene plasma inside the PET bottle for a duration of
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The quality of single crystal diamond obtained by microwave CVD processes has been drastically improved in the last 5 years thanks to surface pre-treatment of the substrates [A. Tallaire, J. Achard, F. Silva, R.S. Sussmann, A. Gicquel, E.... more
The quality of single crystal diamond obtained by microwave CVD processes has been drastically improved in the last 5 years thanks to surface pre-treatment of the substrates [A. Tallaire, J. Achard, F. Silva, R.S. Sussmann, A. Gicquel, E. Rzepka, Physica Status Solidi (A) 201, 2419–2424 (2004); G. Bogdan, M. Nesládek, J. D&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#x27;Haen, J. Maes, V.V. Moshchalkov, K. Haenen, M. D&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#x27;Olieslaeger, Physica
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Abstract The purpose of this paper is to present the first steps towards coupling the IMPGYRO and SOLPS codes for a self-consistent treatment of tungsten as an impurity together with a background plasma. The kinetic IMPGYRO code transfers... more
Abstract The purpose of this paper is to present the first steps towards coupling the IMPGYRO and SOLPS codes for a self-consistent treatment of tungsten as an impurity together with a background plasma. The kinetic IMPGYRO code transfers the effect of tungsten impurities to the SOLPS fluid code, as source/sink terms. As the first step of the coupling, we have implemented in the IMPGYRO code the calculation of the following source/sink terms: 1) electron particle source/sink due to tungsten ionization/ ...
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A precise definition is given of radiative losses and cooling rates; two rates commonly invoked when discussing impurity effects in plasmas. Radiative losses are directly measurable and they enter the total energy balance of the plasma.... more
A precise definition is given of radiative losses and cooling rates; two rates commonly invoked when discussing impurity effects in plasmas. Radiative losses are directly measurable and they enter the total energy balance of the plasma. The electron cooling rate enters the electron thermal energy balance equation. The two rates are identical at steady ionization balance, in the absence of charge transfer. A simple approximate relation exists between them in a strongly ionizing regime, but they are not connected by a simple relation in a recombination regime.
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The formation of carbon dust in DC discharges with graphite electrode is investigated using a numerical model that combines a plasma module, a molecular cluster growth module and a solid particle growth module. The dynamic of particle... more
The formation of carbon dust in DC discharges with graphite electrode is investigated using a numerical model that combines a plasma module, a molecular cluster growth module and a solid particle growth module. The dynamic of particle formation is analyzed and the results are interpreted in terms of negative cluster and particle trapping in the potential well induced by field reversal in the negative glow.
ABSTRACT We developed a model for the nucleation, growth and transport of carbonaceous dust particles in a non-reactive gas dc discharge where the carbon source is provided by cathode sputtering. In a first part, we considered only the... more
ABSTRACT We developed a model for the nucleation, growth and transport of carbonaceous dust particles in a non-reactive gas dc discharge where the carbon source is provided by cathode sputtering. In a first part, we considered only the initial phase of the discharge when the dust charge density remains small with respect to the electron density. We found that an electric field reversal at the entrance of the negative glow region promotes trapping of negatively charged clusters and dust particles, confining them for long times in the plasma and favoring molecular growth. An essential ingredient for this process is electron attachment, which negatively charges the initially neutral clusters. We also showed that the field reversal mechanism can operate to trap negative clusters and particles under both electropositive and strongly electronegative plasma.