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1
Suksila, Thada. "The cathode plasma simulation." Thesis, University of Southern California, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3704256.
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Since its invention at the University of Stuttgart, Germany in the mid-1960, scientists have been trying to understand and explain the mechanism of the plasma interaction inside the magnetoplasmadynamics (MPD) thruster. Because this thruster creates a larger level of efficiency than combustion thrusters, this MPD thruster is the primary cadidate thruster for a long duration (planetary) spacecraft. However, the complexity of this thruster make it difficult to fully understand the plasma interaction in an MPD thruster while operating the device. That is, there is a great deal of physics involved: the fluid dynamics, the electromagnetics, the plasma dynamics, and the thermodynamics. All of these physics must be included when an MPD thruster operates.
In recent years, a computer simulation helped scientists to simulate the experiments by programing the physics theories and comparing the simulation results with the experimental data. Many MPD thruster simulations have been conducted: E. Niewood et al.[5], C. K. J. Hulston et al.[6], K. D. Goodfellow[3], J Rossignol et al.[7]. All of these MPD computer simulations helped the scientists to see how quickly the system responds to the new design parameters.
For this work, a 1D MPD thruster simulation was developed to find the voltage drop between the cathode and the plasma regions. Also, the properties such as thermal conductivity, electrical conductivity and heat capacity are temperature and pressure dependent. These two conductivity and heat capacity are usually definded as constant values in many other models. However, this 1D and 2D cylindrical symmetry MPD thruster simulations include both temperature and pressure effects to the electrical, thermal conductivities and heat capacity values interpolated from W. F. Ahtye [4]. Eventhough, the pressure effect is also significant; however, in this study the pressure at 66 Pa was set as a baseline.
The 1D MPD thruster simulation includes the sheath region, which is the interface between the plasma and the cathode regions. This sheath model [3] has been fully combined in the 1D simulation. That is, the sheath model calculates the heat flux and the sheath voltage by giving the temperature and the current density. This sheath model must be included in the simulation, as the sheath region is treated differently from the main plasma region.
For our 2D cylindrical symmetry simulation, the dimensions of the cathode, the anode, the total current, the pressure, the type of gases, the work function can be changed in the input process as needed for particular interested. Also, the sheath model is still included and fully integrated in this 2D cylindrical symmetry simulation at the cathode surface grids. In addition, the focus of the 2D cylindrical symmetry simulation is to connect the properties on the plasma and the cathode regions on the cathode surface until the MPD thruster reach steady state and estimate the plasma arc attachement edge, electroarc edge, on the cathode surface. Finally, we can understand more about the behavior of an MPD thruster under many different conditions of 2D cylindrical symmetry MPD thruster simulations.
2
Beck, Arnaud. "Simulation N-Corps d'un plasma." Phd thesis, Observatoire de Paris, 2008. http://tel.archives-ouvertes.fr/tel-00359057.
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La simulation N-Corps d'un plasma consiste à calculer l'interaction coulombienne mutuelle entre N particules chargées. Nous avons adapté un algorithme N-Corps de type ``code en arbre'', utilisé avec succès dans le cas gravitationnel, pour la simulation de plasmas. Pour l'instant, nous avons trouvé deux champs d'applications pour lesquels cette technique est particulièrement bien adaptée.Tout d'abord les problèmes d'expansion de plasma dans le vide. Ce genre de simulation fait coexister des densités d'ordres de grandeur très différents. Certaines zones peuvent avoir un comportement hydrodynamique pendant que d'autres sont peuplées de particules avec des trajectoires balistiques car trop énergétiques. Les protons, notamment, peuvent ainsi être accélérés à des vitesses requises pour la fusion. Ce type de problème, faisant intervenir une interface plasma-vide, est pratiquement impossible à étudier à l'aide des techniques de simulation courantes (e.g. codes MHD, Vlasov, Fokker-Planck, ...).
L'autre champ d'application est celui de la simulation des plasmas modérément ou fortement couplés qui concerne de nombreux plasmas de laboratoire, mais également des plasmas astrophysiques, tels, par exemple, la zone convective du Soleil. Dans les plasmas dits couplés, les collisions ``binaires proches'' entre charges ne peuvent pas être négligées. Or, les modèles numériques de type Fokker-Planck, très majoritairement utilisés pour simuler des plasmas faiblement collisionnels, n'en tiennent pas compte ce qui les rends inadéquats à ce type de plasma. La technique N-Corps, quant à elle, gère chaque particule individuellement et peut très bien décrire précisément les trajectoires de particules subissant ce genre de déviation violente.
3
Hendricks, Brian Reginald. "Simulation of plasma arc cutting." Thesis, Peninsula Technikon, 1999. http://hdl.handle.net/20.500.11838/1245.
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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1999The simulation of Plasma Arc Cutting is presented in this study. The plasma arc cutting process employs a plasma torch with a very narrow bore to produce a transferred arc to the workpiece. A technique for modelling plasma arc cutting has been developed by applying the thermo-metallurgical model to the process and integrating a model of material removal to this model. The model is solved using the finite element method using the FE package SYSWORLD, more specifically SYSWELD. The objective is to determine the minimum energy required to cut a plate of some thickness using this virtual model. The characteristics of the cut need to exhibit the characteristics of a "high quality cut". The model presented can predict the kerf size given certain process variable settings. The numerical results obtained are assessed by conducting experiments. By maintaining Ill1rumum energy input cost savings can be made through energy savings, limiting additional finishing processes and reducing expense of shortening the electrode and nozzle lifetimes. The modelling of the PAC process using virtual design techniques provides a cost-effective solution to the manufacturing industries with respect to process specification development. This plays an important role in South Africa's transition into a competitive global market. It is envisaged that the model will provide an alternative more efficient, non-destructive means of determining the optimum process variable settings for the plasma arc cutting process.
4
Loewenhardt, Peter Karl. "A Vlasov plasma simulation code." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27586.
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A 1-1/2 dimensional, electromagnetic Vlasov plasma simulation code, relativistically correct, was constructed and tested. The code can deal with one or two species, each with a Maxwellian distribution and a possible drift velocity. The code also allows external fields, such as a laser, to be included in the simulations. Simulations of Landau damping, the two-stream instability and stimulated Raman scattering were carried out and compared with theory and with the results of the particle code EM1. When dealing with electrostatic problems, the Vlasov code gave results agreeing very closely with theory in both non-relativistic and relativistic regimes. Here the Vlasov code preformed better than EM1 which had problems with background noise and longer run times. When a laser field was included within the simulations, however, the Vlasov code produced some spurious features, unlike EM1. These anomalous features may be caused by aliasing, recurrence or by some other unknown effect. Since realistic results are produced as well, it is believed that this problem can be overcome. When a very high intensity laser was included in the simulations the Vlasov code produced much better results but was plagued by very long run times.Science, Faculty of
Physics and Astronomy, Department of
Graduate
5
Liu, Hongqin 1956. "Simulation of a plasma particle generator." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31571.
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The goal of this research was to simulate the nucleation and particle growth in a tubular plasma particle generator and investigate the effects of various entrance and boundary conditions on the particle size distribution and production rate.The fluid flow is laminar and its domain is two-dimensional axi-symmetric and a radial quench gas injection is introduced. The method of moments was used to model the particle generation and growth starting with the dynamic aerosol equation and the assumption of a log-normal distribution function. The governing equations are solved numerically and the velocity, concentration, temperature, particle size and density profiles are obtained for various entrance and boundary conditions.
The following conclusions were reached: increasing the length of the generator tube or metal concentration gives more product, larger particle size and narrower size distribution; higher quench gas injection rates or entrance flow rate produces finer particles with a broader size distribution; increasing entrance temperature leads to smaller particles with narrower size distribution.
In addition, for a quick prediction, an artificial neural network (ANN) model was used. The ANN was trained with the data from the numerical simulations. Within the ranges of conditions examined, the output can be obtained in few seconds rather than several hours needed in the original simulations.
6
Koen, Etienne. "A Simulation Approach to Plasma Waves." Doctoral thesis, KTH, Rymd- och plasmafysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-151415.
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Electrostatic waves in the form of Broadband Electrostatic Noise (BEN) have been observed inthe Earth’s auroral region associated with high geomagnetic activity. Their broad frequencyspectrum consists of three electrostatic modes, namely electron plasma, electron acoustic andbeam-driven modes.A 1D Particle-in-Cell (PIC) simulation was developed to investigate the characteristics ofthe electrostatic waves found in such a plasma. Dispersion, phase space and spatial electricfield diagrams were constructed from the output of the PIC simulation which was used todescribe the wave dispersion and spatial field structures found in a plasma. A three electroncomponent plasma was studied using a Maxwellian distribution function to model their ve-locities. Beam-driven waves were found to dominate the frequency spectrum while electronplasma and electron acoustic waves were damped for a high beam velocity. Furthermore, for ahigh beam velocity, solitary waves are generated by electron holes (positive potentials), givingrise to a bipolar spatial electric field structure moving in the direction of the beam. Increasingthe beam temperature allows the beam electrons to mix more freely with the hot and coolelectrons, which leads to electron plasma and electron acoustic waves being enhanced whilebeam-driven waves are damped. Decreasing the beam density and velocity leads to dampingof beam-driven waves, while electron plasma and electron acoustic waves are enhanced.The electron acoustic mode was studied with the addition of a static background magneticfield. When the angle of wave propagation is perfectly perpendicular to the backgroundmagnetic field, a set of harmonics, called Bernstein modes, were produced. These modesare characterized by their nodes being furtherly displaced along the wave vector axis for anincrease in the node (harmonic) number. The model was further generalized by allowing theangle of wave propagation, θ, with respect to the magnetic field to be varied, thus enabling thestudy of the obliquely propagating electron acoustic mode. Both the amplitude and frequencyof the electron acoustic mode was found to decrease as θ increases.Measurements in Saturn’s magnetosphere have shown the co-existence of two electron (hotand cool) components. The electron velocities are best described by a κ-distribution (insteadof a Maxwellian) which has a high-energy tail. Using an adapted PIC simulation, the study ofelectron plasma and electron acoustic waves was extended by using a κ-distribution to describethe electron velocities with low κ indices. Electron acoustic waves are damped over most wavenumber ranges while electron plasma waves are weakly damped at low wave numbers anddamped for all other wave numbers. Furthermore, the study was extended by introducingthe motion of ions to study the ion acoustic waves in Saturn’s magnetosphere. While the ionacoustic mode was found to be relatively insensitive to the κ indices of the electrons, it isfound to be sensitive to the electron temperature and density ratios.QC 20140922
7
Hanahoe, Kieran. "Simulation studies of plasma wakefield acceleration." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/simulation-studies-of-plasma-wakefield-acceleration(ac0c9742-2aed-493b-8356-e30f3db97e1e).html.
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Plasma-based accelerators offer the potential to achieve accelerating gradients orders of magnitude higher than are typical in conventional accelerators. A Plasma Accelerator Research Station has been proposed using the CLARA accelerator at Daresbury Laboratory. In this thesis, theory and the results of particle-in-cell simulations are presented investigating experiments that could be conducted using CLARA as well as the preceding VELA and CLARA Front End. Plasma wakefield acceleration was found to be viable with both CLARA and CLARA Front End, with accelerating gradients of GV/m and 100 MV/m scale respectively. Drive-witness and tailored bunch structures based on the CLARA bunch were also investigated. Plasma focus- ing of the VELA and CLARA Front End bunches was studied in simulations, showing that substantial focusing gradient could be achieved using a passive plasma lens. A plasma beam dump scheme using varying plasma density is also presented. This scheme allows the performance of a passive plasma beam dump to be maintained as the bunch is decelerated and has some advantages over a previously proposed method.
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Sarret, Frédéric. "Simulation numérique de dépôts céramiques plasma." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0066/document.
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Cette thèse apporte une contribution à la simulation numérique de la construction de dépôts dans le cadre de la projection plasma type APS (Atmospheric Plasma Spraying). Ce travail est focalisé sur la construction d’un volume représentatif du revêtement en prenant en compte l’ensemble des phénomènes propres au procédé, tels que la nature de l’écoulement de gaz, la cinétique (multiphasique, mouillabilité) et la thermique (transferts thermiques, résistance thermique de contact, solidification) durant l’impact et l’empilement de particules. Une méthode numérique particulière, appelée VOF-SM (Volume Of Fluid - Sub Mesh), est développée. La simulation de l’impact d’un jet instationnaire et turbulent de plasma ArH2 sur un substrat a été réalisée pour définir la nature de l’écoulementen proche paroi et le transfert thermique entre cet écoulement et le substrat. Les phénomènes propres à l’impact de particules ont été intégrés au code de calcul Thétiset validés indépendamment par comparaison à des solutions analytiques et combinés par comparaison à un cas d’étude expérimentale millimétrique. Enfin, une étude d’impacts successifs de particules de Zircone Yttriée sur un substrat en acier a été menée, par une approche en similitudes thermique et cinétique pour pallier la difficulté de la résolution à petites échellesThis PhD thesis is a contribution to the numerical simulation of the plasma sprayedcoating build-up by APS process (Atmospheric Plasma Spraying). This work focuses onthe build-up of a representative volume of the coat considering a great range of phenomenonappearing in APS process such as gas flow properties, kinetic (multiphase flow,wettability) and thermal (heat transfers, thermal contact resistance, solidification) duringthe impact and steaking of particles. An original numerical method, named VOF-SM(Volume Of Fluid - Sub Mesh) is developped. The simulation of the impact of an unsteadyand turbulent ArH2 plasma flow is carried out in order to define the gas flow closeto the wall and heat transferred to the substrate by the plasma. Specific phenomena of theimpact of particles were incorporated into the CFD code (Thétis) and validated independentlyby caparison with analytical solutions, then together combined by the comparisonto a millimeter size impact experimental data. Finally, a study of successive impacts ofYttria-Stabilized Zirconia particles onto a steel substrate was carried out by thermal andkinetic approach similarities to overcome the difficulty of resolving small scales
9
Honda, Mitsuru. "Transport simulation of tokamak plasmas including plasma rotation and radial electric field." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136227.
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Frignani, Michele <1978>. "Simulation of gas breakdown and plasma dynamics in plasma focus devices." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/414/.
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Ohta, Hiroaki. "Molecular dynamics simulation of the plasma-surface interaction during plasma etching processes." Kyoto University, 2004. http://hdl.handle.net/2433/145252.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第11119号
エネ博第97号
新制||エネ||27(附属図書館)
22669
UT51-2004-L916
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 近藤 克己, 教授 佐野 史道, 教授 斧 髙一
学位規則第4条第1項該当
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EL, KANZARI ZAKIA. "Modelisation et simulation numerique d'un plasma helicon." Nantes, 1997. http://www.theses.fr/1997NANT2004.
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La presente etude est consacree a la modelisation et a la simulation numerique des plasmas d'argon et d'oxygene depuis leur creation par une source plasma helicon jusqu'a leur arrivee a l'extremite de la chambre de diffusion contenant le substrat a traiter. Le but de ce travail est de contribuer a une meilleure comprehension et a une optimisation des processus de depot de couches minces de silice amorphe sur un substrat de silicium. L'etude des processus de dissociation et d'ionisation dans la source helicon est realisee a l'aide d'un modele cinetique sans dimension (od) qui determine les concentrations des particules chargees arrivant dans la chambre de diffusion. Ce modele montre notamment que l'oxygene moleculaire se dissocie tres fortement dans la source plasma. L'etude du comportement electrique du plasma dans la chambre de diffusion est realisee, pour la premiere fois dans la litterature dans le cas d'un plasma helicon, a l'aide d'un modele pic-mcc (particle-in-cell monte carlo collision) optimise et bien adapte aux plasmas basse pression faiblement collissionnels. Le modele pic-mcc a ete valide en utilisant des mesures experimentales obtenues au laboratoire. Ce code pic-mcc fournit les grandeurs caracteristiques du plasma (potentiel, densite de charge, fonctions de distribution de l'energie des electrons et des ions, etc. ) en fonction des parametres d'entree (pression du gaz, temperature electronique initiale, champ magnetique, polarisation du substrat, etc. ). L'etude parametrique montre notamment que les densites de plasma les plus elevees sont obtenues dans la partie superieure de la chambre de diffusion pour des temperatures electroniques voisines de 6 ev et une pression proche de 1mtorr. Cette etude a egalement montre que l'addition d'un champ magnetique autour de la chambre de diffusion en plus de celui applique a la source, permet un meilleur confinement et une plus grande homogeneite du plasma
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Aithal, Shashikant Madhava. "Numerical simulation of plasma and reacting flows /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487942739806253.
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Chen, Zhaoyang. "Molecular dynamics simulation of charged dusts in plasmas." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971847266.
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Yoo, Chan. "Plasma confinement optimization of the versatile toroidal facility for ionospheric plasma simulation experiments." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/97781.
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Sugita, Satoru. "Etude par simulation numérique du transport radial dans le plasma de bord du tokamak." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10010/document.
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Il est maintenant accepté expérimentalement que les filaments de plasma alignés sur le champ magnétique, appelés “blobs”, jouent un rôle important dans le transport dans le plasma de bord. Dans cette thèse, les phénomènes fondamentaux du transport dans le plasma de bord sont étudiés en mettant l'accent sur le phénomène de filaments plasma. Dans un premier temps, les mécanismes de propagation de blobs uniques sont envisagés. Puis la génération de blobs par la turbulence de bord est étudiée, et le transport turbulent est discuté entant que phénomène collectif. Des particularités du transport turbulent, incluant les blobs auto-organisés, sont reliées à un transport de type Bohm (c'est à dire des perturbations avec des corrélations radiales longues, et un coefficient de transport effectif quisuit la dépendance Bohm). De plus, en prolongement de ce travail, un effort initial vers une transposition du transport non-local au plasmade bord est décriteRecently, it has been accepted that magnetic field aligned plasma filaments, referred to as "blobs" play important roles in the transport of Scrape-off Layer (SoL) plasmas. In this thesis, putting an emphasis on the plasma blob phenomenon, we study fundamental processes of SoL transport using numerical simulation. At first, weinvestigate the propagation mechanisms of single and isolated blobs.Next, we study the generation of blobs from edge turbulence, and discuss the SoL turbulent transport as a collective phenomenon. Features of turbulent transport, which includes the self-organized blobs in SoL, are identified as Bohm-like transport (i.e., the perturbation with long radial correlations and the effective transport coefficient that follows the dependence of Bohm-like transport). Additionally, as an advancement of study, we describe an initial effort to extend the view of non local transport to edge plasmas
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Koen, Etienne. "A Simulation Approach to High-Frequency Plasma Waves." Licentiate thesis, KTH, Rymd- och plasmafysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-106822.
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Electrostatic waves in the form of Broadband Electrostatic Noise (BEN) have been observed in the Earth's auroral region associated with high geomagnetic activity. This broad frequency spectrum consists of three electrostatic modes, namely electron plasma, electron acoustic and beam-driven modes. These modes are excited in a plasma containing three electron components: hot, cool and beam electrons. A 1D Particle-in-Cell (PIC) simulation was developed to investigate the characteristics of the electrostatic waves found in such a plasma. Dispersion, phase space and spatial electric field diagrams were constructed from the output of the PIC simulation which were used to describe the wave dispersion and spatial field structures found in a plasma. The PIC code used a three electron component plasma with Maxwellian distributions to describe the electron velocity distributions. Beam-driven waves were found to dominate the frequency spectrum while electron plasma and electron acoustic waves are damped for a high beam velocity. Furthermore, for a high beam velocity, solitary waves are generated by electron holes (positive potentials), giving rise to a bipolar spatial electric fi eld structure moving in the direction of the beam. Increasing the beam temperature allows the beam electrons to mix more freely with the hot and cool electrons, which leads to electron plasma and electron acoustic waves being enhanced while beam-driven waves are damped. Decreasing the beam density and velocity leads to damping of beam-driven waves, while electron plasma and electron acoustic waves are enhanced. Measurements in Saturn's magnetosphere have found the co-existence of two electron (hot and cool) components. The electron velocities are best described by a kappa-distribution (instead of a Maxwellian) which has a high-energy tail. Using an adapted PIC simulation the study of electron plasma and electron acoustic waves was extended by using a kappa-distribution to describe the electron velocities with low indices. Electron acoustic waves are damped over most wave number ranges. Electron plasma waves are weakly damped at low wave numbers and damped for all other wave numbers.QC 20121205
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Eliasson, Bengt. "Numerical simulation of kinetic effects in ionospheric plasma." Licentiate thesis, Uppsala : Dept. of Information Technology, Univ, 2001. http://www.it.uu.se/research/reports/lic/2001-004/2001-004-nc.pdf.
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Lowe, Robert Edward. "Simulation of electron acceleration at collisionless plasma shocks." Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246324.
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Hornsby, William Anestis. "Kinetic simulation of plasma transport in magnetic turbulence." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497934.
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Liau, Vui Kien. "Computer simulation of high pressure non-equilibrium plasma." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406716.
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Broemstrup, Ingmar. "Advanced lagrangian simulation algorithms for magnetized plasma turbulence." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8730.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Boon, Hau Tan. "Process Simulation of Plasma Gasification for Landfill Waste." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229804.
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The growing amount of landfill waste within the EU could pose a problem in the future should there not be any effective treatment methods. This study aims to investigate the performance of landfill waste in a plasma gasification process by simulating the process in ASPEN Plus. The investigation is focused on the energy recovery potential of RDF based on composition and heating value of syngas, and cold gas efficiency (CGE). The plasma gasification system consists of a shaft gasifier and a separate tar cracking reactor where high temperature plasma is used for conversion of tar compounds considered in the model, which are toluene and naphthalene. In addition, the model is divided into five sections, namely drying, pyrolysis, char gasification, melting and tar cracking. Mass and energy balance of the system was performed to better understand the system. The results show that the plasma gasification system was able to produce a syngas with a LHV of 4.66 MJ/Nm3 while improving syngas yield by attaining a higher content of hydrogen. Thus, the plasma tar cracking of tar compounds can achieve a clean syngas and improve syngas yield. Parameter study on effect of ER show that syngas has higher heating value and CGE at lower ER. On the other hand, preheated air can help recover energy from the system while lowering the ER required for the char gasification process to meet the heat demand from partial combustion. The findings implied that landfill waste has energy potential by using a suitable treatment process such as plasma gasification.
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Cordier, Stéphane. "Modélisation mathématique et simulation numérique du plasma magnétosphérique." Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0010.
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Cette these est consacree a la modelisation mathematique du transport des particules chargees le long des lignes de champ magnetique terrestre. L'hyperbolicite des modeles multi-moments et multi-especes utilises en physique des plasmas spatiaux et des modeles hydrodynamiques couples par quasineutralite est une condition necessaire de stabilite du probleme linearise. L'analyse de l'hyperbolicite conduit a des limitations sur les flux de chaleur et les vitesses relatives des ions qui sont depassees experimentalement pour des altitudes superieures a 1800 km. L'analyse mathematique permet donc de caracteriser explicitement les domaines de validite de ces modeles. Le systeme euler quasineutre qui decrit un plasma electrons-ions a deux temperatures est un systeme non strictement hyperbolique non lineaire sous forme non conservative. Il est obtenu comme limite formelle du systeme euler-poisson lorsque la longueur de debye tend vers 0. L'existence globale de solutions du systeme euler-poisson pour un plasma est obtenue par une methode de glimm. Les solutions ondes de choc admissibles pour le modele asymptotique euler quasineutre sont definies comme les limites faibles de solutions ondes progressives du systeme euler-poisson. Ces solutions sont construites par une etude de systeme dynamique. Les chocs non collisionnels ainsi obtenus verifient la conservation de la masse, l'impulsion et l'energie; l'analyse impose une relation de saut supplementaire: l'adiabaticite des electrons. Ces relations de saut permettent de resoudre le probleme de riemann et de developper une methode numerique de type roe
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Montillet, Denis. "Simulation et optimisation de la projection plasma robotisée." Montpellier 2, 1999. http://www.theses.fr/1999MON20154.
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Cette these a pour sujet la realisation d'un simulateur pour la projection plasma robotisee. Nous proposons une approche utilisant la cao-robotique pour diminuer la complexite et le temps de programmation des robots. Dans le premier chapitre on definit, apres un etat de l'art sur la modelisation de la projection plasma, un modele de depot repondant aux contraintes de la simulation dans une cao-robotique en vue d'une future utilisation industrielle. Le modele de depot est base sur une caracterisation experimentale. Le second chapitre porte sur la definition et l'integration de moyens de simulation pour la projection plasma dans une cao robotique. Le simulateur utilise les donnees issues du modele de depot ainsi que la definition geometrique, cinematique et dynamique de la cellule virtuelle de projection. En cours de simulation, une carte de depot donnant les evolutions de son epaisseur est generee sur la piece 3d. Dans le troisieme chapitre, nous definissons deux methodes d'optimisation permettant d'augmenter la qualite de la projection en tenant compte des contraintes liees a la robotique ainsi que celles liees au procede. Une de ces methodes permet, grace a une formulation originale du probleme, de donner des solutions rapides pour l'optimisation des conditions de projection sur une piece 3d complexe. Finalement, nous presentons une validation experimentale du simulateur sur une piece industrielle.
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Dannert, Tilman. "Gyrokinetische Simulation von Plasmaturbulenz mit gefangenen Teilchen und elektromagnetischen Effekten." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974209708.
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Paro, Autumn D. "Modeling High Altitude Electron Density Plumes Using Direct Numerical Simulation." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/210.
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Electron densities form field-aligned structured regions in the natural ionosphere and after a high altitude nuclear explosion (HANE). These electron densities, known as plumes, are made up of many smaller individual field-aligned regions called striations. Striation modeling for systems effects has traditionally been done use a statistical approach. This statistical approach evolves different moments of the electron density. Due to lack of test data it has never been validated. The purpose of this project was to use a direct numerical simulation to solve equations governing the differential motion of individual striations. It was done in five steps: 1) Transport a single striation, 2) solve potential equation, 3) combine transport and potential equations, 4) optimize combined solver, and 4) simulate a fully-striated plume for comparison with the statistical model.
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Alaluss, Khaled, and Peter Mayr. "Modellierung - Simulation des Plasma-Schweißens zur Entwicklung innovativer Schweißbrenner." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-225849.
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- An Plasmaschweißbrennern treten starke thermomechanische Beanspruchungen aufgrund der ablaufenden thermophysikalischen Teilprozesse auf. Diese können durch funktionsgerechte werkstoffliche, konstruktive und fertigungstechnische Brennergestaltung bewerkstelligt und die Thermobilanz und Lebensdauer der Brenner verbessert werden.
- Anhand des entwickelten strömungs-thermomechanischen/magneto-hydro-dynamischen Simulationsmodells wurden werkstofflich-konstruktive Lösungsansätze für Entwicklung von physikalischen Prozesswirkprinzipien der betrachteten Plasma-Schweißprozessvarianten erarbeitet.
- Differente Einflussgrößen des Plasmaschweißprozesses wurden erfasst, analysiert und ihre Wirkung auf Prozessverhalten und Brennerkonstruktion ermittelt.
- Die damit gewonnenen Erkenntnisse wurden für werkstoffliche, technisch-konstruktive Brennerentwicklung bzgl. der Ausführungsgeometrien, Prozessgaszuführung und Brennerkühlung genutzt.
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Glesner, Colin Christopher. "Development of Magnetic Nozzle Simulations for Space Propulsion Applications." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74947.
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A means of space propulsion using the channeling of plasma by a divergent magnetic field, referred to as a magnetic nozzle has been explored by a number of research groups. This research develops the capability to apply the high order accurate Runge-Kutta discontinuous Galerkin numerical method to the simulation of magnetic nozzles. The resistive magnetohydrodynamic model of plasma behavior is developed for these simulations. To facilitate this work, several modeling capabilities are developed, including the implementation of appropriate inflow and far-field boundary conditions, the application of a technique for correcting errors that develop in the divergence of the magnetic field, and a split formulation for the magnetic field between the applied and the perturbed component. This model is then applied to perform a scaling study of the performance of magnetic nozzles over a range of Bk and Rm. In addition, the effect of the choice of simulation domain size is
investigated. Finally, recommendations for future work are made.Master of Science
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Martirosyan, Vahagn. "Atomistic simulations of H2 and He plasmas modification of thin-films materials for advanced etch processes." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT101/document.
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Ce travail de thèse aborde l’un des défis technologiques liés au développement de nouvelles générations de transistors (FinFET, FDSOI), pour lesquels la gravure de couches ultraminces révèle plusieurs problèmes. En particulier, la gravure des espaceurs nitrure (SiN) doit être réalisée avec une précision nanométrique sans endommager les couches sous-jacentes, étape qui ne peut plus être réalisée par des plasmas conventionnels continus. Afin de dépasser cette limitation, une approche innovante a été récemment développée (dite Smart-Etch), qui s’appuie sur l'implantation d’ions légers et se déroule en deux étapes. Premièrement, le matériau à graver est exposé à un plasma ICP ou CCP d’hydrogène (H2) ou d’hélium (He); dans une deuxième étape, la couche modifiée est retirée sélectivement par gravure humide ou exposition à des réactifs gazeux. Afin d’appréhender les mécanismes fondamentaux de la première étape et assister le développement de cette nouvelle technologie, des simulations de dynamique moléculaire (MD) ont été réalisées pour étudier l'interaction des plasmas H2/He avec des couches de Si/SiN. La MD a été utilisée pour examiner comment la modification de ces substrats est affectée par l’énergie ionique, la dose ionique, la composition ionique ou le rapport flux de radicaux/ flux d’ions (dans le cas d’un plasma H2). En accord avec les expériences, les simulations de bombardement ionique He+ ou Hx+ (x = 1-3) sur Si/SiN montrent que l’implantation ionique est auto-limitée, et que l’évolution de la surface se déroule en deux étapes : une rapide modification en volume (sans gravure) suivie d'une saturation lente et de la formation d'une couche implantée stable en régime permanent (état stationnaire). Les mécanismes d'endommagement induit par les ions (rupture des liaisons Si-Si ou Si-N, piégeage/désorption d’He ou H2, formation de groupes SiHx (x = 1-3) en profondeur), sont étudiés et permettent d’apporter de nouveaux éléments de compréhension aux technologies Smart-Cut et Smart-Etch. L’exposition de substrats Si/SiN à un plasma H2 (impacts d’ions Hx+ et de radicaux H) a également été étudiée pour différentes conditions plasma. Dans ce cas, une transformation auto-limitée est observée mais les couches modifiées/hydrogénées sont simultanément gravées pendant l'implantation ionique, à un taux 10 fois inférieur pour SiN par rapport à Si. Les simulations montrent que modifier des substrats Si/SiN avec une précision nanométrique nécessite un contrôle prudent de l’énergie et du flux des ions incidents. En particulier, les faibles doses ioniques doivent être évitées car l’évolution de la surface ne peut pas être contrôlée précisément en régime transitoire (modification rapide). Dans les plasmas H2, les énergies ioniques élevées induisent des couches modifiées plus épaisses mais des taux d'hydrogénation plus faibles et moins homogènes. La composition ionique et le rapport flux de radicaux/ flux ions (Γ) doivent également être controllés avec précaution, notamment car la vitesse de gravure du matériau augmente avec Γ, ce qui empêche entre-autre la possibilité du Smart-Etch pour le silicium. Les simulations MD réalisées dans cette thèse permettent de clarifier divers phénomènes inexpliqués observés dans le Smart-Etch expérimentalement, et de révéler quelques problèmes possibles dans ce nouveau procédé. Finalement, une gamme de paramètres plasma est proposée pour optimiser cette première étape de Smart-Etch et contrôler la modification de SiN avec une précision sous-nanométriqueThis PhD thesis focuses on technological challenges related to the development of advanced transistors (FinFET, FDSOI), where the etching of thin films reveals several issues. In particular, the etching of silicon nitride spacers should be achieved with a nanoscale precision without damaging the underlayers, a step which cannot be addressed by conventional CW plasmas. To overpass this limitation, an innovative approach was recently developed (so-called Smart Etch), which is based on light ion implantation and composed of two steps. First, the material to be etched is modified by exposure to a hydrogen (H2) or helium (He) ICP or CCP plasma; in a second step, the modified layer is selectively removed using wet etching or gaseous reactants only. To support the fundamental understanding of the first step and assist the development of this new technology, molecular dynamics (MD) simulations were performed to study the interaction between silicon/silicon nitride films and hydrogen/helium plasmas. MD was used to investigate how the substrates modification is affected by the ion energy, the ion dose, the ion composition or the radical-to-ion flux ratio (in the case of a H2 plasma). In agreement with experiments, simulations of He+ or Hx+ (x=1-3) ion bombardment of Si/SiN show that a self-limited ion implantation takes place with a surface evolution composed of two stages: a rapid volume modification (with no etching) followed by a slow saturation and the formation of a stable He- or H- implanted layer at steady state. The mechanisms of ion-induced damage (Si-Si or Si-N bond breaking, He or H2 trapping/desorption, SiHx (x=1-3) complex creation) are investigated and allow to bring new insights to both the Smart Cut and Smart Etch technologies. Si/SiN exposure to various H2 plasma conditions (with both Hx+ ions and H radicals) was then studied. In this case, a self-limited transformation is observed but the H-modified layers are simultaneously etched during the ion implantation, at a rate ~10 times smaller for SiN compared to Si. Simulations show that to modify Si/SiN thin films with a nanoscale precision by H2 or He plasmas, both the ion energy and the ion flux have to be controlled very cautiously. In particular, low ion doses, where the substrate evolution is in rapid modification stage, must be avoided since the substrate evolution cannot be precisely controlled. In H2 plasmas, high ion energies induce thicker modified layers but smaller and less homogeneous hydrogenation rates. The ion composition and the radical-to-ion flux ratio Γ must be considered as well, since the etch rate increases with Γ, compromising even the possibility to achieve a Smart Etch of silicon. The MD simulations performed in this thesis enable to clarify various unexplained phenomena seen in the Smart-Etch experimentally, and reveal some possible issues in this new process. In the end, a range for plasma parameters is proposed to optimize this first step of the Smart Etch process and to control the modification of SiN with a sub-nanoscale precision
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Dieckmann, Mark Eric. "A survey of elementary plasma instabilities and ECH wave noise properties relevant to plasma sounding by means of particle in cell simulations." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327557.
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Pateau, Amand. "Simulation multi-échelle de la gravure profonde du silicium par procédé Bosch." Nantes, 2014. http://archive.bu.univ-nantes.fr/pollux/show.action?id=8e1ed5e3-4695-4ca6-b965-76b9fecea337.
Full textAbstract:
Cette étude porte sur le développement d’une approche multi-échelle pour la simulation de la gravure profonde du silicium par procédé Bosch. Ce travail a été effectué dans le cadre d’un contrat CIFRE entre l’Institut des Matériaux Jean Rouxel et STMicroelectronics Tours. Cette approche multi-échelle est composée de trois modules permettant d’étudier l’évolution spatio-temporelle du profil gravé. Le premier module comporte le modèle cinétique de la décharge plasma. Il permet le calcul des densités et flux d’espèces prises en compte dans le schéma réactionnel. Ce modèle a été appliqué séparément aux mélanges SF6/O2/Ar et C4F8. Le deuxième module basé sur la technique Monte-Carlo permet le calcul des fonctions de distribution angulaires et énergétiques des ions traversant la gaine. Les différents flux d’espèces chimiquement actives et les fonctions de distribution calculés par ces deux modules sont ensuite injectés, comme paramètres d’entrée, dans le module de gravure. Ce dernier est basé sur une approche Monte-Carlo cellulaire qui permet de décrire l’évolution spatio-temporelle des profils gravés, leur composition chimique à la surface ainsi que la vitesse de gravure. Une telle approche est bien adaptée à la prédiction des profils de gravure profonde du silicium sous un procédé Bosch en fonction des paramètres " machine ". L’influence des paramètres " machine " sur le comportement cinétique du plasma, la dynamique de la gaine et l’évolution des profils a été étudiée. Les comparaisons des résultats issus du modèle cinétique et ceux de l’expérience montrent un accord satisfaisant. D’autre part, les profils simulés sont prometteurs avant la calibration du modèle de gravureThis thesis is dedicated to the development of a multi-scale approach for the simulation of the deep silicon etching under Bosch process. The project has been done under CIFRE contract between the Institut des Matériaux Jean Rouxel and STMicroelectronics Tours. This multi-scale approach is composed of three modules allowing the study of the time and space evolution of the etched silicon profile. The first module is a plasma kinetic model. It calculates the densities and fluxes of the species taken into account in the reaction scheme. This model is applied to the SF6/O2/Ar and C4F8 plasma mixtures. The second module is based on the Monte-Carlo technique and allows the calculation of the energy and angular distribution functions of positive ions through the sheath. The fluxes of the chemically reactive species and the ion distributions calculated by those two modules are then injected as input parameters in the etching module. The latter is based on a cellular Monte-Carlo approach allowing the description of the time and space evolution of the etched profiles, their chemical composition along the surface and the etching rate. Such techniques are used to predict the etched profile evolution under Bosch process as a function of machine parameters. The influence of the machine parameters on the plasma kinetic, sheath dynamic and profile evolution has been studied. Good agreements between the simulations from the kinetic model and the experiment have been shown. On the other side, The simulated profiles are promising before the model calibration
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Vigstrand, Oscar. "Development of an absorption model for gas discharge lamp simulation." Thesis, Malmö universitet, Malmö högskola, Institutionen för materialvetenskap och tillämpad matematik (MTM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-42518.
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Ultraviolet (UV) light has been used for disinfection purposes for over 100 years. Irradiation by UV light is a method to disinfect surfaces in order to prevent microbiological growth. At Tetra Pak this is of great importance as they are manufacturer of filling machines. Those filling machines must ensure a certain level of sterility on all packages produced. The irradiation process can be simulated using Geant4 which is a software package that tracks particles through matter. The simulation model used today does not consider the absorption of photons inside of medium-pressure UV lamps. By understanding the absorption that takes place in the lamp, one can quantify how changes in the design would impact the emitter output. In this master's thesis, the aim is to develop a model that can describe the interaction of photons with a medium-pressure UV lamp. An absorption model was suggested and developed with the assumption of local thermodynamical equilibrium and existing Hg radiative data. A simulation including the collision process in Geant4 was used. In this collision process the non-radiative transition probabilities were assumed to be the same as that of the radiative, this was done in order to demonstrate how it can be done. It resulted in collisions populating other states allowing more transitions to be present in the final output spectrum. The collision process and a method for computing the Einstein's emission coefficient with the software package General Relativistic Atomic Structure Package is proposed as future work.I över 100 år har ultraviolet (UV) ljus använts till desinficering. UV bestrålning är en metod för att desinficera ytor med målet att förhindra mikrobiologisk tillväxt. För Tetra Pak som är ledande inom tillverkning av fyllmaskiner är det extra viktigt. Förpackningarna inuti fyllningsmaskinerna måste garantera en viss nivå av sterilitet för alla förpackningar. Dagens simuleringar av medeltrycks UV lampa utförs i Geant4 som är ett mjukvarupaket som möjliggör följandet av partiklar genom olika medium. Detta görs utan att ta hänsyn till absorptionen av fotoner. Genom att förstå absorptionen som sker i lampans gas kan man kvantifiera hur förändringar i design skulle påverka emittorns utgående effekt. I detta examensarbete är målet att utveckla en modell som kan beskriva hur fotoner växelverkar med gasen i en medeltrycks UV lampa. En modell utvecklas och föreslås med antagandet att lokalt termodynamisk jämvikt råder och att enbart Hg strålnings data används. En simulering med en kollisionsprocess i Geant4 inkluderades. I denna kollisionsprocess antas den icke-optiska övergångssannolikheten vara densamma som för de optiska övergångarna. Detta inkluderades för att demonstrera hur en sådan process kan gå till. Detta resulterade i att kollisionerna populerade andra tillstånd vilket gjorde att dessa övergångar visade sig i utgående spektrum. Kollisionsprocessen och en metod för att beräkna Einsteins emissions koefficient med mjukvarupaketet General Relativistic Atomic Structure Package föreslås även som framtida arbete.
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Nowak, R. W. (Robert Walter). "Discrete cascade universal multifractal simulation and analysis." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29915.
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Historically discrete multiplicative cascade models have been developed to mimic some of the characteristics of fully-developed turbulence. Some of these models have been found to be of much more general relevancy and have been used to simulate and analyse many different kinds of simple geophysical and other scaling fields. The desire to describe more complex processes has led to the invention of multivariate multiplicative cascade models. Of these the simple "complex cascade model" is considered in detail in this thesis. The background theory of Levy random variables and discrete scalar cascades is covered and a description of the various existing analysis techniques is provided. Two analysis techniques are described and tested on complex cascade simulations. The new "adjacent data points" (ADP) method is found to be superior to the traditional analysis technique. A discussion of the difficulties which may be encountered when analysing recorded complex data is included.
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Deist, David W. "A simulation of plasma motion in the polar ionosphere." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA286166.
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Lee, Kin-ho, and 李健豪. "Simulation of single-particle inductively coupled plasma-mass spectrometry." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196478.
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Time-resolved Inductively Coupled Plasma –Mass Spectrometry (ICP-MS) is a versatile tool for the analysis of single particles such as air particles, nanoparticles, and biological cells. In this study, the processes of particle vaporization and analyte atom diffusion and ionization in the ICP were investigated using computer simulation. Gold nanoparticles of particle diameter 10 to 250 nm were used as the model particle. The parameters of the model were optimized with respect to the experimental data. The relative importance of these parameters was investigated. Simulated ICP-MS intensity versus sampling depth for different particle size was calculated.
Two models of particle vaporization, namely heat-transfer-limited and mass-transfer-limited, were adopted to describe the kinetics of vaporization of the gold nanoparticles. The rate of particle vaporization of the limiting model in each 5-µs time step was used in the simulation. The heat-transfer-limited process dominates at lower position of the ICP. The mass-transfer-limited process takes over at sampling depth of 4mm or above where the ICP temperature is higher than 4000K. The simulation assumed that the gold atoms vaporized from the particle in each time step diffuse independently. The number density of the gold atoms was calculated using the Chapman-Enskog diffusion theory for each subsequent time step. The degree of ionization of the gold atoms was estimated using Saha equation and was assumed to be dependent on the plasma temperature only. The simulated ICP-MS intensity at any instant was the sum of the gold ions in the ion plumes from all previous time steps that pass through a 1-mm sampler cone.
The effects of several simulation parameters on the calculated ICP-MS intensity were investigated. The simulation depth profile of ICP-MS intensity of 100-nm gold nanoparticle was compared to the experimental ICP-MS depth profile. The ICP-MS intensity depends strongly on the ionization temperature of the plasma and the evaporation coefficient of the analyte. The ICP temperature profile, gas velocity, ionization temperature and evaporation coefficient were optimized for the best fit of simulated results to the experimental data.
Simulated calibration curves of gold nanoparticles of nominal diameter of 10 nm to 250 nm are non-linear at any sampling depth. The calibration curve rolls off at high mass due to incomplete vaporization of the larger particles in the ICP. The calibration curve at high sampling depth concaves upward in the low mass range because of significant diffusion loss of the analyte atoms for the small particles.published_or_final_version
Chemistry
Master
Master of Philosophy
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Salou, Pierre. "Interaction ion‐surface : simulation de l'interaction plasma‐paroi (ITER)." Phd thesis, Université de Caen, 2013. http://tel.archives-ouvertes.fr/tel-00915747.
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Les matériaux de couverture des réacteurs à fusion nucléaire par confinement magnétique subissent un environnement agressif ; le flux intense de particules extraites du plasma attaque les parois du réacteur, engendrant la pulvérisation de la matière en surface. Cette pulvérisation est à l'origine de l'érosion des parois mais aussi de la pollution du plasma, ainsi, afin de maitriser la réaction de fusion dans des réacteurs de plus en plus complexes, il est impératif de bien comprendre les phénomènes d'interaction plasma-paroi. Cette thèse a pour but l'étude de la pulvérisation des matériaux des réacteurs de fusion nucléaire (carbone et tungstène), pour cela nous proposons de simuler le flux de particules chargées du plasma par des faisceaux d'ions monochargés d'énergies inférieures à la dizaine de keV. Cette étude est basée sur la méthode du collecteur, aussi afin de s'affranchir des problèmes liés aux polluants (notamment pour l'étude du carbone), nous avons conçu et réalisé un nouveau dispositif permettant l'analyse des collecteurs in situ par spectroscopie des électrons Auger. Les résultats obtenus donnent accès à l'évolution de la distribution angulaire en fonction des paramètres d'irradiation comme la masse du projectile (de hélium au xénon) ou l'énergie (de 3 keV à 9 keV).
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Cannon, Patrick. "Numerical simulation of wave-plasma interactions in the ionosphere." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/80076/.
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Ionospheric modification by means of high-power electromagnetic (EM) waves can result in the excitation of a diverse range of plasma waves and instabilities. This thesis presents the development and application of a GPU-accelerated finite-difference time-domain (FDTD) code designed to simulate the time-explicit response of an ionospheric plasma to incident EM waves. Validation tests are presented in which the code achieved good agreement with the predictions of plasma theory and the computations of benchmark software. The code was used to investigate the mechanisms behind several recent experimental observations which have not been fully understood, including the effect of 2D density inhomogeneity on the O-mode to Z-mode conversion process and thus the shape of the conversion window, and the influence of EM wave polarisation and frequency on the growth of density irregularities. The O-to-Z-mode conversion process was shown to be responsible for a strong dependence of artificially-induced plasma perturbation on both the EM wave inclination angle and the 2D characteristics of the background plasma. Allowing excited Z-mode waves to reflect back towards the interaction region was found to cause enhancement of the electric field and a substantial increase in electron temperature. Simulations of O-mode and X-mode polarised waves demonstrated that both are capable of exciting geomagnetic field-aligned density irregularities, particularly at altitudes where the background plasma frequency corresponds to an electron gyroharmonic. Inclusion of estimated electrostatic fields associated with irregularities in the simulation algorithm resulted in an enhanced electron temperature. Excitation of these density features could address an observed asymmetry in anomalous absorption and recent unexplained X-mode heating results reported at EISCAT. Comparing simulations with ion motion allowed or suppressed indicated that a parametric instability was responsible for irregularity production. Simulation of EM wave fields confirmed that X-mode waves are capable of exceeding the threshold for parametric instability excitation under certain conditions.
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Salou, Pierre. "Interaction ion-surface : simulation de l’interaction plasma-paroi (ITER)." Caen, 2013. http://www.theses.fr/2013CAEN2035.
Full textAbstract:
Les matériaux de couverture des réacteurs à fusion nucléaire par confinement magnétique subissent un environnement agressif ; le flux intense de particules extraites du plasma attaque les parois du réacteur, engendrant la pulvérisation de la matière en surface. Cette pulvérisation est à l’origine de l’érosion des parois mais aussi de la pollution du plasma, ainsi, afin de maitriser la réaction de fusion dans des réacteurs de plus en plus complexes, il est impératif de bien comprendre les phénomènes d’interaction plasma-paroi. Cette thèse a pour but l’étude de la pulvérisation des matériaux des réacteurs de fusion nucléaire (carbone et tungstène), pour cela nous proposons de simuler le flux de particules chargées du plasma par des faisceaux d'ions monochargés d'énergies inférieures à la dizaine de keV. Cette étude est basée sur la méthode du collecteur, aussi afin de s'affranchir des problèmes liés aux polluants (notamment pour l'étude du carbone), nous avons conçu et réalisé un nouveau dispositif permettant l'analyse des collecteurs in situ par spectroscopie des électrons Auger. Les résultats obtenus donnent accès à l'évolution de la distribution angulaire en fonction des paramètres d'irradiation comme la masse du projectile (de hélium au xénon) ou l'énergie (de 3 keV à 9 keV)The wall materials of magnetic confinement in fusion machines are exposed to an aggressive environment; the reactor blanket is bombarded with a high flux of particles extracted from the plasma, leading to the sputtering of surface material. This sputtering causes wall erosion as well as plasma contamination problems. In order to control fusion reactions in complex reactors, it is thus imperative to well understand the plasma-wall interactions. This work proposes the study of the sputtering of fusion relevant materials. We propose to simulate the charged particles influx by few keV single-charged ion beams. This study is based on the catcher method; to avoid any problem of pollution (especially in the case of carbon) we designed a new setup allowing an in situ Auger electron spectroscopy analysis. The results provide the evolution of the angular distribution of the sputtering yield as a function of the ion mass (from helium to xenon) and its energy (from 3 keV to 9 keV)
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Zhan, Yiyi. "PC-based visual simulation of high pressure arc plasma." Thesis, University of Liverpool, 2011. http://livrepository.liverpool.ac.uk/3433/.
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Parachoniak, Ronald D. "Numerical experiments using an electrostatic, relativistic plasma simulation code." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26023.
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A 1-1/2 dimensional electrostatic, relativistic, plasma simulation model was constructed, implemented on the UBC FPS array processor, and tested by solving three problems in plasma physics. The model will handle a variety of different initial conditions including cold plasmas, cold beams, and drifting maxwellians. Relativistic particle velocities are properly modelled and up to two species of particles may be specified. The numerical experiments run with the model included cold plasma oscillations, cold and warm two-stream instabilities, and Landau damping. Results of the simulations were compared to theory and excellent agreement was obtained in all the cases studied. The model may now be used with confidence to research various (relativistic) electrostatic problems. It could also be modified to make it fully electromagnetic, in which case it would be useful for simulating many additional phenomena, including laser-plasma interactions.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Allioux, Renaud. "Simulation de l'environnement plasma de Ganymède : contraintes radiatives pour l'orbiteur JGO-JUICE." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1760/.
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Ce travail de thèse vise à comprendre et modéliser l'environnement plasma proche de Ganymède dans le contexte de la mission spatiale EJSM/JUICE. Nous avons pour cela construit un modèle permettant de déterminer les caractéristiques des populations de particules énergétiques autour de Ganymède et réalisé plusieurs simulations modélisant l'interaction de la magnétosphère de Ganymède avec le plasma ambiant. La première partie de cette étude s'attache à développer un code de simulation particulaire, s'appuyant sur un calcul des trajectoires des particules dans l'environnement magnétisé de Ganymède et utilisant les propriétés du théorème de Liouville pour prédire les caractéristiques des populations d'ions et d'électrons de très hautes énergies autour de Ganymède. Nous avons étudié comment le cône de perte existant au-dessus des calottes polaires était affecté par les effets de rayons de Larmor finis et analysé les possibilités de piégeage dans les régions équatoriales. Nous pourrons ainsi décrire aussi précisément que possible l'organisation de l'espace des phases des ions et des électrons entre 0 et 4 rayons de Ganymède. Plusieurs modèles représentant le champ magnétique de Ganymède ont été testés et utilisés. Il a été montré qu'un modèle paramétrique multipolaire donne l'approximation la plus satisfaisante des observations du magnétomètre de Galileo. A partir de ce modèle magnétique, nous avons découvert que l'accumulation de particules dans les ceintures de radiations de Ganymède restait limitée. Les flux aux basses et moyennes énergies (quelques dizaines de keV pour les ions et quelques MeV pour les électrons) sont sensiblement les mêmes que ceux attendus dans la magnétosphère de Jupiter (sans les perturbations de Ganymède), malgré l'existence de particules piégées (en particulier des électrons), ce qui traduit l'absence de processus d'accumulation. La protection offerte par les lignes de champ fermées contre les particules d'énergies moyennes à fortes a été également démontrée. Nous avons ensuite appliqué ce modèle à l'étude de l'environnement radiatif auquel serait soumis un orbiteur potentiel proche de Ganymède. Ce travail a permis de démontrer que, par rapport au milieu Jovien ambiant, la présence de Ganymède et de son champ magnétique réduisait d'au moins 50% la dose attendue pour un orbiteur circulaire à basses altitudes. Différentes configurations orbitales ont été étudiées, nous confortant dans la nécessité de prendre en compte cette réduction dans les spécifications de la mission. Enfin, nous avons adapté un code de simulation hybride, développé par Ronan Modolo au LATMOS, au cas de l'interaction du plasma Jovien avec la magnétosphère de Ganymède. Le développement et l'utilisation de ce code a permis de décrire certains phénomènes inédits et d'étudier de manière originale le mouvement des espèces ioniques dans l'environnement de Ganymède, illustrant l'importance des phénomènes cinétiques dans cette micro magnétosphère. La comparaison des résultats de ce modèle aux observations de Galileo a permis de valider l'algorithme et les hypothèses de simulationThe purpose of this work is to study the environment of Ganymede in the context of the EJSM-JUICE mission designed by ESA. Several simulations were performed to model the interaction of the Jovian plasma with Ganymede and its magnetic field. The first part was dedicated to the development of a particle simulation using Liouville Theorem in order to study the characteristics of high energy particle populations in the vicinity of Ganymede. The formation of loss cones over the polar caps and trapping region near the equator were investigated in order to describe the energy/pitch angle repartition of the various populations from 0 to 4 Ganymede radii. Several magnetic models and configurations were considered and compared to Galileo's observations. It is shown that a multipolar parametric magnetic model is the most realistic. We have shown that, even if trapping of particles (especially electrons) is possible in the region of close field lines, the formation of dense radiation belt is highly improbable due to upstream magnetic field compression that strongly perturbs the symmetry of the magnetic field. The density reduction, due to the shielding offered by the close field line and the surface absorption itself, was also studied. This model was then applied to the study of the radiation dose expected for a potential EJSM-JGO orbiter in close orbits. This part of the study was done in collaboration with ESA and EADSAstrium. It revealed that the influence of Ganymede and its magnetic field could reduce the expected dose received by the spacecraft by about 50% for orbit below 1000 km, compared to an undisturbed environment. Several orbital configurations were studied. They all show the importance of the reduction effect and the necessity of taking in consideration the shielding of Ganymede in the specification of the mission. Finally we have used a hybrid code developed by Ronan Modolo to simulate the interaction of the Jovian plasma with Ganymede's magnetosphere. We obtain innovative results compared to pure MHD models due to the possibility to take into account ion kinetic effects. We have identified asymmetries in the plasma dynamics close to near Ganymede and differences in the motion of the protons and oxygen
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Meige, Albert. "Simulations numériques de plasmas basse pression : applications aux doubles couches." Toulouse 3, 2006. http://www.theses.fr/2006TOU30203.
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Un modèle particle-in-cell / Monte Carlo collisions (pic/mcc) unidimensionnel est utilsé pour simuler un plasma inductif. Un champ électrique radiofréquence (rf) est utilisé pour modéliser le chauffage inductif. L’amplitude du champ est non-uniforme et sa direction perpendiculaire à celle du déplacement des électrons. Ce modèle de plasma inductif permet de confirmer de récents résultats expérimentaux démontrant la possibilité de former des doubles couches électriques au sein de plasmas sans courant. Les doubles couches étudiées par le passé, aussi bien numériquement qu’expérimentalement, ont toujours été imposées par différence de potentiel ou en forçant un courant électrique dans le plasma. C’est en ce sens que les résultats présentés ici diffèrent de ceux précédemment reportés. La simulation prédit la formation d’un faisceau d’ions supersoniques résultant des ions accélèrés par le saut de potentiel de la double couche. L’existence de ce faisceau d’ions supersoniques est confirmée par fluorescence induite par laser (nonperturbative laser-induced fluorescence). La simulation montre aussi qu’à basse pression, lorsque le libre parcours moyen des électrons est du même ordre de grandeur ou plus grand que le système, la fonction de distribution en énergie des électrons (eedf) est quasi-Maxwellienne, à l’exception de sa queue, dépeuplée pour des énergies supérieures au potentiel plasma. Ce dépeuplement est principalement dû à la perte aux parois des électrons les plus rapides. Un nouveau schéma de simulation hybride (ions particulaires et électrons particulaires et Boltzmann), permettant de simuler des plasmas hautes pressions et hautes densités, en des temps de calculs relativement faibles, est proposé. Les résultats obtenus avec ce modèle hybride “amélioré” sont bien plus proches de ceux d’une simulation pic, que le sont ceux d’une simulation hybride classique. Ce modèle est appliqué à la simulation de décharges électronégatives et confirme des résultats expérimentaux démontrant la possibilité de formation de doubles couches propagatives. En particulier, les paramètres critiques contrôllant cette formation dans la simulation corroborent ceux de l’expérienceInductive plasmas are simulated by using a one-dimensional particle-in-cell simulation including Monte Carlo collision techniques (pic/mcc). To model inductive heating, a non-uniform radio-frequency (rf) electric field, perpendicular to the electron motion is included into the classical particle-in-cell scheme. The inductive plasma pic simulation is used to confirm recent experimental results that electric double layers can form in current-free plasmas. These results differ from previous experimental or simulation systems where the double layers are driven by a current or by imposed potential differences. The formation of a super-sonic ion beam, resulting from the ions accelerated through the potential drop of the double layer and predicted by the pic simulation is confirmed with nonperturbative laser-induced fluorescence measurements of ion flow. It is shown that at low pressure, where the electron mean free path is of the order of, or greater than the system length, the electron energy distribution function (eedf) is close to Maxwellian, except for its tail which is depleted at energies higher than the plasma potential. Evidence supporting that this depletion is mostly due to the high-energy electrons escaping to the walls is given. .
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Li, Huayu. "Lattice Boltzmann simulation of laser interaction with weakly ionized plasmas." Diss., Connect to online resource - MSU authorized users, 2008.
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Lucken, Romain. "Theory and simulation of low-pressure plasma transport phenomena : Application to the PEGASES Thruster." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX046/document.
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Le domaine de la physique des plasmas froids a émergé avec les premières découvertes fondamentales en physique atomique et en physique des plasmas il y a plus d’un siècle. Toutefois, ce domaine a été rapidement orienté vers les applications. L’une des plus importantes dans la première moitié du XXème est le "Calutron" (California University Cyclotron), inventé par E. Lawrence à Berkeley, qui faisait partie du projet Manhattan, et utilisé comme un spectromètre de masse pour séparer les isotopes de l’uranium. Dans un rapport du projet Manhattan daté de 1949, D. Bohm fait deux observations qui sont fondamentales pour la physique des plasmas froids :(i) Les ions doivent avoir une énergie cinétique minimales lorsqu’ils entrent dans la gaine du plasma, estimée à Te/2, Te étant la température électronique.(ii) Le transport du plasma à travers un champ magnétique est augmenté par des instabilités.La propulsion électrique par plasma est utilisée pour des satellites militaires et des sondes spatiales depuis les années 1960 et a suscité un intérêt grandissant ces vingt dernières années avec le développement des applications commerciales des technologies spatiales. Néanmoins, les mêmes questions que celles auxquelles D. Bohm était confronté, c’est-à-dire le transport multidimensionnel, l’interaction plasma-gaine, et les instabilités, se posent toujours. La théorie et les simulations sont d’autant plus importantes pour la conception des systèmes de propulsion électrique que les tests en conditions réelles nécessitent le lancement d’un satellite dans l’espace.Dans ce travail, nous établissons les équations du transport multidimensionnel dans un plasma isotherme, nous proposons un critère de gaine qui permet de rendre compte de la saturation du champ magnétique dans un plasma froid et faiblement ionisé, et nous modélisons le refroidissement des électrons à travers le filtre magnétique du propulseur PEGASES (Plasma Propulsion with Electronegative Gases). Toutes les théories sont motivées et validées par un grand nombre de simulations particulaires PIC bi-dimensionnelles, en utilisant le code LPPic qui a été partiellement développé dans le cadre du projet. Enfin, les cas de simulation sont étendus à une décharge inductive à plasma dans l’iode, avec un nouvel ensemble de section efficaces de réactionThe field of low temperature plasma physics has emerged from the first fundamental discoveries in atom and plasma physics more than a century ago. However, it has soon become very much driven by applications. One of the most important of them in the first half of the XXth century is the "Calutron" (California University Cyclotron) invented by E.~Lawrence in Berkeley, that was part of the Manhattan project, and operated as a mass spectrometer to separate uranium isotopes. In a 1949 report of the Manhattan project, D.~Bohm makes two observations that are fundamental for low-temperature plasma physics.(i) The ions must have minimum kinetic energy when they enter the plasma sheath estimated to T_e/2 , Te being the electron temperature in eV ;(ii) Plasma transport across a magnetic field is enhanced by instabilities.Plasma electric propulsion is used on military satellites and space probes since the 1960s and has gained more and more interest for the last twenty years as space commercial applications were developing. However, the same questions as the ones D.~Bohm was faced with, namely multi-dimensional transport, plasma sheath interaction, and instabilities, arise. Theory and simulation are even more important for electric space propulsion systems design since testing in real conditions involves to launch a satellite into space.In this work, we derive the equations of the multi-dimensional isothermal plasma transport, we establish a sheath criterion that causes the magnetic confinement to saturate in low-temperature, weakly ionized plasmas, and we model the electron cooling through the magnetic filter of the PEGASES (Plasma Propulsion with Electronegative Gases) thruster. All the theories are driven and validated with extensive two-dimensional particle-in-cell (PIC) simulations, using the LPPic code that was partially developed in the frame of this project. Finally, the simulation cases are extended to an iodine inductively coupled plasma (ICP) discharge with a new set of reaction cross sections
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Esmond, Micah Jeshurun. "Two-dimensional, Hydrodynamic Modeling of Electrothermal Plasma Discharges." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81447.
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A two-dimensional, time-dependent model and code have been developed to model electrothermal (ET) plasma discharges. ET plasma discharges are capillary discharges that draw tens of kA of electric current. The current heats the plasma, and the plasma radiates energy to the capillary walls. The capillary walls ablate by melting and vaporizing and by sublimation. The newly developed model and code is called the Three-fluid, 2D Electrothermal Plasma Flow Simulator (THOR). THOR simulates the electron, ion, and neutral species as separate fluids coupled through interaction terms. The two-dimensional modeling capabilities made available in this new code represent a tool for the exploration and analysis of the physics involved in ET plasma discharges that has never before been available.
Previous simulation models of ET plasma discharges have relied primarily on a 1D description of the plasma. These models have often had to include a tunable correction factor to account for the vapor shield layer - a layer of cold ablated vapor separating the plasma core from the ablating surface and limiting the radiation heat flux to the capillary wall. Some studies have incorporated a 2D description of the plasma boundary layer and shown that the effects of a vapor shield layer can be modeled using this 2D description. However, these 2D modeling abilities have not been extended to the simulation of pulsed ET plasma discharges. The development of a fully-2D and time-dependent simulation model of an entire ET plasma source has enabled the investigation of the 2D development of the vapor shield layer and direct comparison with experiments. In addition, this model has provided novel insight into the inherently 2D nature of the internal flow characteristics involved within the plasma channel in an ET plasma discharge. The model is also able to capture the effects of inter-species interactions.
This work focuses on the development of the THOR model. The model has been implemented using C++ and takes advantage of modern supercomputing resources. The THOR model couples the 2D hydrodynamics and the interactions of the plasma species through joule heating, ionization, recombination, and elastic collisions. The analysis of simulation results focuses on emergent internal flow characteristics, direct simulation of the vapor shield layer, and the investigation of source geometry effects on simulated plasma parameters. The effect of elastic collisions between electrons and heavy species are shown to affect internal flow characteristics and cause the development of back-flow inside the ET plasma source. The development of the vapor shield layer has been captured using the diffusion approximation for radiation heat transfer within the ET plasma source with simulated results matching experimental measurements. The relationship between source radius and peak current density inside ET plasma discharges has also been explored, and the transition away from the ablation-controlled operation of ET plasma discharges has been observed.Ph. D.
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Daldorff, Lars Kristen Selberg. "Numerical Simulation as a Tool for Studying Waves and Radiation in Space." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9517.
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Azimi, Mohammad. "Study of the linear and nonlinear damping in plasma via simulation." Thesis, Umeå universitet, Institutionen för fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-162714.
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Benmouffok, Malyk. "Caractérisation théorique du plasma lors de l'application d'un courant impulsionnel : application à l'allumage des moteurs." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30159/document.
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Le contexte économique et écologique difficile ainsi que la réglementation en matière d'émissions de CO2 poussent les industriels de l'automobile à améliorer les moteurs à allumage commandé. L'une des voies d'amélioration envisagées est l'admission de mélanges pauvres ou fortement dilués par des gaz d'échappement (EGR) dans la chambre de combustion. La difficulté de ce type de fonctionnement est l'initiation de l'allumage. Afin de pallier ce problème, les systèmes d'allumage sont étudiés et tout particulièrement l'étincelle. Cette décharge est à l'origine de l'apparition d'un plasma et la compréhension des mécanismes impliqués dans le transfert d'énergie entre ce plasma et le gaz réactif environnant est essentielle. Ce travail s'intéresse à la modélisation de l'étincelle dans sa phase d'arc électrique afin de pouvoir prédire le comportement hydrodynamique de l'arc et la propagation de l'onde de choc. Les modèles transitoires bidimensionnels ou tridimensionnels utilisés sont basés sur le logiciel @ANSYS Fluent couplé à des fonctions utilisateurs développées au sein de l'équipe AEPPT. Ils s'appuient dans un premier temps sur la littérature afin de comprendre le comportement général de la décharge, puis sur des configurations expérimentales utilisées dans le cadre du projet ANR FAMAC. Les simulations sont dans un premier temps et en majorité réalisées dans l'air sur des configurations simplifiées de type pointe-pointe afin de valider le modèle. Ensuite, une étude est faite dans une configuration de réacteur où l'arc est généré entre les bornes d'une bougie d'allumage. Le modèle permet de démontrer le rôle de chacun des paramètres initiaux des simulations ainsi que leur impact sur l'écoulement du plasma. L'influence de la prise en compte du champ magnétique est montrée dans le cadre d'un arc impulsionnel nanoseconde. Enfin, le modèle a permis de montrer le rôle d'un écoulement laminaire latéral en direction d'une décharge de type conventionnelle générée par une bobine d'allumage Audi. L'ensemble de ces résultats pourront être le point de départ d'une étude énergétique sur les systèmes d'allumage ainsi que d'une réflexion concernant la compréhension de l'initiation de la combustionThe economic/ecological context and the CO2 regulation by the "euro" standards lead the automotive industry to improve the spark ignited engines. A way of improvement is the admission of a lean mixture or of a diluted mixture by recirculation of exhaust gases in the combustion chamber. The main difficulty in these conditions is to start the combustion. To overcome this problem, the ignition systems are studied and more particularly the spark. This discharge leads to the apparition of plasma and the understanding of the energy transfer mechanisms between this plasma and the reactive mixture is essential. This work is focus on the modeling of a spark during its electrical arc phase in order to predict the hydrodynamic behavior of the arc and the shock wave propagation. The 2D and 3D transient models are based on ANSYS Fluent coupled with user defined functions developed by the AEPPT team. First, the simulation is based on data from literature review in order to understand the general behavior of the discharge. Then, the model uses experimental configuration developed during the ANR FAMAC project. Simulations are mainly realized in air using simplified configurations (pin-to-pin configurations) in order to valid the model. Then, a study is done in a vessel configuration using real sparkplug geometry. This model allows us to show the role of each initial parameter as well as their impact on the plasma flow. The magnetic field influence is also determined for a nanosecond arc discharge. Finally, the model is used in order to determine the role of a cross flow on a discharge generated by a conventional Audi ignition coil. All these results could be the beginning of an energetic study on ignition systems and could lead to a discussion on the understanding of initiation of the combustion process
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Ziadé, Pierre. "Simulation de composants électroniques aux fréquences téraHertz." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20104.
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L'objectif de ce travail de thèse est l'exploitation des oscillations de plasma tridimensionnelles dans des diodes à base d'InGaAs et de GaN, matériaux de grand intérêt pour les applications térahertz à cause de la haute mobilité électronique du premier et des fortes interactions électrons-phonons optiques dans le second. Ce travail s'insère dans le contexte d'études récentes dans lesquelles l'utilisation de dispositifs basés sur l'excitation d'ondes de plasma tridimensionnelles a été proposée pour des applications térahertz, à l'heure où les ondes de plasma bidimensionnelles demeurent très limitées en puissance. Cette étude est menée à travers le développement d'un outil numérique de simulation basé sur le modèle hydrodynamique couplé à un solveur de Poisson unidimensionnel. La réponse des diodes à différentes perturbations optiques et électriques est alors évaluée à travers la description du régime petit-signal, et l'influence sur les résonances de plasma des différents paramètres des diodes est mise en évidence pour l'InGaAs et pour le GaN. Une résolution matricielle de l'équation de Poisson à deux dimensions est également présentée en vue d'un couplage ultérieur avec le modèle hydrodynamique à deux dimensions, ce qui permettrait éventuellement une étude plus approfondie des ondes de plasma dans les transistors. En outre, vu que les paramètres d'entrée du modèle hydrodynamique sont tirés d'un simulateur Monte Carlo dont les paramètres d'entrée sont directement calculés à partir de la structure de bandes du matériau, une partie préliminaire à la simulation des dispositifs, et qui implique le calcul de la structure de bande des matériaux par la méthode semi-empirique du pseudopotentiel, est aussi traitéeThe objective of this thesis is the analysis of three-dimensional plasma oscillations in diodes based on InGaAs and GaN, materials of great interest for terahertz applications because of the high electron mobility of the first and the strong electron-optical phonons interactions in the second. This work falls within the context of recent studies in which the use of devices based on the excitation of three-dimensional plasma waves has been proposed for terahertz applications, at a time when two-dimensional plasma waves remain very limited in emission power. This study is conducted through the development of a numerical simulation based on the hydrodynamic model coupled to a one-dimensional Poisson solver. The response of diodes at different optical and electrical excitations is then evaluated through the description of small-signal regime, and the influence on plasma resonances of the various parameters of the diodes is demonstrated for InGaAs and GaN. A matrix resolution of the two-dimensional Poisson equation is also presented for a subsequent coupling with the two-dimensional hydrodynamic model, which would eventually allow a more thorough study of plasma waves in transistors. In addition, since the input parameters of the hydrodynamic model are derived from a Monte Carlo simulator whose input parameters are directly calculated from the band structure of the material, a preliminary study to devices simulation, which involves the calculation of the materials band structure by the semi-empirical pseudopotential method, is also considered