Download or read book A New Modelling of the Cross field Transport in Diverted Edge Plasma written by Serafina Baschetti and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Le fonctionnement à l'équilibre du réacteur à fusion de prochaine génération, ITER, nécessitera le développement d'outils numériques fiables permettant d'estimer les paramètres d'ingénierie clés à un coût de calcul raisonnable. Les codes de transport répondent à cette exigence car ils reposent sur des équations fluides bidimensionnelles qui sont moyennées sur les fluctuations temporelles, de la même manière que les modèles « Reynolds Averaged Navier-Stokes » couramment utilisés dans la communauté des fluides neutres. De plus, les codes de transport peuvent rassembler la plupart des ingrédients physiques régissant le comportement du plasma de bord, ainsi que une topologie magnétique réaliste et la géométrie du mur. Cependant, leur prévisibilité est limitée par une description inadéquate des flux turbulents perpendiculaires aux lignes de champ magnétique, qui influent fortement e confinement du plasma sur de longues périodes. En effet les flux perpendiculaires, supposés diffusifs, sont grossièrement déterminés par des coefficients de diffusion homogènes ou "ad-hoc", ou par des procédures à boucle de rétroaction appliquées "a-posteriori" à des données expérimentales. Motivés par ces questions, nous présentons dans ce travail un nouveau modèle pour estimer de manière cohérente la distribution des flux perpendiculaires dans les codes de transport, lorsque les plasmas en régime permanent sont concernés. La stratégie consiste à introduire des outils numériques efficaces largement utilisés dans la communauté de la turbulence neutre en physique des plasmas. Deux concepts clés sont inspirants dans la communauté des fluides neutres. Le premier est "l'hypothèse de Boussinesq". Elle consiste à linéariser le tenseur de contraintes de Reynolds dansl'équation de Navier-Stokes moyennée dans le temps via une relation de diffusion dans laquelle le terme de proportionnalité est appelé « eddy viscosity ». Le deuxième concept est le modèle "k-epsilon", dans lequel les équations de transport pour l'énergie turbulente cinétique moyenne et le taux d'échange d'énergie entre les structures turbulentes sont conçues de manière semi-empirique. A l'équilibre, k et epsilon permettent une estimation auto-cohérente de l'« eddy viscosity », intégrant ainsi l'impact de la turbulence sur les flux moyennés à l'état d'équilibre. Ces concepts ne peuvent pas être appliqués directement pour enrichir la modélisation des flux perpendiculaires dans les plasmas en raison de différentes propriétés de turbulence. Par conséquent, nous suggérons une adaptation du modèle k-epsilon pour les flux neutres à des plasmas à confinement magnétique, où deux équations de transport pour l'énergie cinétique turbulente et son taux de dissipation sont dérivées algébriquement, y compris la physique de l'instabilité d'interchange linéaire, responsable de la distribution "ballonnée" du transport perpendiculaire dans le bord du plasma. Différentes approches sont décrites pour fermer les paramètres libres : premièrement, une procédure de boucle de rétroaction pour optimiser les résultats numériques comparés avec un test expérimental. Ensuite, on assume une loi d'échelle de référence pour la largeur du profil de flux de chaleur dans la SOL, déterminée empiriquement à partir des mesures expérimentales du flux de chaleur sur le divertor externe dans diverses machines. Le nouveau modèle est intégré au package de transport SolEdge2D-EIRENE, développé en collaboration entre le CEA et le laboratoire M2P2 de l'Université d'Aix-Marseille. Les résultats numériques à l'état d'équilibre sont discutés et on démontre qu'ils se comparent favorablement aux données expérimentales soit à l'outer midplane que au divertor externe. De plus, on montre que les distributions de diffusivité présentent des asymétries poloïdales cohérentes avec la distribution "ballonnée" du transport perpendiculaire observée dans les mêmes conditions dans les codes de premier principe et les expériences.
Download or read book Cross field Plasma Transport and Main Chamber Recycling in Diverted Plasmas on Alcator C Mod written by Brian LaBombard and published by . This book was released on 2000 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling of Far SOL Plasma Transport in NSTX written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For better understanding and characterization of non-diffusive transport occurring in the NSTX tokamak edge plasma, we performed extensive simulations of NSTX edge plasmas with the multi-fluid two-dimensional UEDGE code by using realistic model for impurity sputtering sources and hybrid model for anomalous cross-field transport. Our cross-field transport model incorporates the effects of non-diffusive intermittent transport by introducing anomalous convective velocities whose spatial profile is adjusted for each ion charge state to match available experimental data. The research in 2002-2005 financial years was focused on the following areas: (i) development of capabilities for UEDGE simulation of NSTX spectroscopy data (i.e., the 3D real-geometry postprocessor UEDGE tools for comparison between UEDGE and experimental data), (ii) simulation of multi-diagnostic data from NSTX with UEDGE, (iii) study of anomalous cross-field convective transport of impurity ions, (iv) analysis of divertor plasma opacity to resonance radiation, and (v) study the effects of ballooning-like anomalous cross-field transport and spherical-torus magnetic configuration on parallel plasma flows in the SOL.
Download or read book Summary of UNM Work on Edge Plasma Modelling written by and published by . This book was released on 1996 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The B2 two dimensional edge plasma code has found widespread application in modelling scrape-off layer and divertor plasma conditions for ITER and CIT (BPX). The transport physics in B2 consists of the so-called standard model that employs 2D Braginskii equations for the background plasma, anomalous cross-field transport coefficients, and classical along-field transport coefficients computed in the straight cylinder approximation. Although the code displays acceptable convergence characteristics for the class of problems of interest in ITER and CIT applications, it is remarkably resistant to improvements in the physics model. That is, extensions to including the symmetry breaking drift flows and wall or divertor plate generated impurity species in the code have not met with success - satisfactory solution convergence has not been achieved in various test problems. Given that the drift flows have been identified as being an important component of any fluid model that attempts to reconcile computational results with experimental observations and that control of impurities is vitally important in present and subsequent generations of high power machines, successful numerical models of edge plasmas must be clearly robust enough to handle a significantly expanded physical model.
Download or read book On the Edge of Magnetic Fusion Devices written by Sergei Krasheninnikov and published by Springer. This book was released on 2021-09-09 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the current state of understanding concerning edge plasma, which bridges hot fusion plasma, with a temperature of roughly one million degrees Kelvin with plasma-facing materials, which have melting points of only a few thousand degrees Kelvin. In a fact, edge plasma is one of the keys to solution for harnessing fusion energy in magnetic fusion devices. The physics governing the processes at work in the edge plasma involves classical and anomalous transport of multispecies plasma, neutral gas dynamics, atomic physics effects, radiation transport, plasma-material interactions, and even the transport of plasma species within the plasma-facing materials. The book starts with simple physical models, then moves on to rigorous theoretical considerations and state-of-the-art simulation tools that are capable of capturing the most important features of the edge plasma phenomena. The authors compare the conclusions arising from the theoretical and computational analysis with the available experimental data. They also discuss the remaining gaps in their models and make projections for phenomena related to edge plasma in magnetic fusion reactors.
Download or read book On the Edge of Magnetic Fusion Devices written by Sergei Krasheninnikov and published by Springer Nature. This book was released on 2020-09-07 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the current state of understanding concerning edge plasma, which bridges hot fusion plasma, with a temperature of roughly one million degrees Kelvin with plasma-facing materials, which have melting points of only a few thousand degrees Kelvin. In a fact, edge plasma is one of the keys to solution for harnessing fusion energy in magnetic fusion devices. The physics governing the processes at work in the edge plasma involves classical and anomalous transport of multispecies plasma, neutral gas dynamics, atomic physics effects, radiation transport, plasma-material interactions, and even the transport of plasma species within the plasma-facing materials. The book starts with simple physical models, then moves on to rigorous theoretical considerations and state-of-the-art simulation tools that are capable of capturing the most important features of the edge plasma phenomena. The authors compare the conclusions arising from the theoretical and computational analysis with the available experimental data. They also discuss the remaining gaps in their models and make projections for phenomena related to edge plasma in magnetic fusion reactors.
Download or read book Core Fueling and Edge Particle Flux Analysis in Ohmically and Auxiliary Heated NSTX Plasmas written by V. A. Soukhanovskii and published by . This book was released on 2002 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Edge Sol and Diverter Plasma Turbulence and Macroscopic Transport written by Prof. Sergi Krasheninnikov and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last few years, it was clearly shown that cross-field transport in the far SOL could be significantly faster than previously thought and that this transport exhibited convective rather then diffusive features. As a result, in high density cases the plasma coming into the SOL from the core recycled at the wall of the tokamak main chamber, rather than flowing into the divertor and recycling there, as the conventional picture of edge plasma flows would suggest. It was also shown that coherent structures, often called ''blobs'', played very important roles in the particle and energy transport inside the SOL region for both L and H confinement modes. The blobs seen in the SOL are extended along the magnetic field lines and have a plasma density two to three times higher than the ambient SOL plasma density and poloidal and radial scales of about 1 cm. In experimental measurements, the blobs propagated in radial direction towards the chamber wall with a velocity {approx} 10{sup 5} cm/s, and the contribution of non-diffusive flux associated with transport of blobs to the total particle flux in the far SOL attained 70-90%. In addition, recent assessment of experimental data and theoretical models shows that plasma propagation into the SOL during ELM is somewhat similar to that of blobs.
Download or read book Monte Carlo Model of Neutral particle Transport in Diverted Plasmas written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The transport of neutral atoms and molecules in the edge and divertor regions of fusion experiments has been calculated using Monte-Carlo techniques. The deuterium, tritium, and helium atoms are produced by recombination in the plasma and at the walls. The relevant collision processes of charge exchange, ionization, and dissociation between the neutrals and the flowing plasma electrons and ions are included, along with wall reflection models. General two-dimensional wall and plasma geometries are treated in a flexible manner so that varied configurations can be easily studied. The algorithm uses a pseudo-collision method. Splitting with Russian roulette, suppression of absorption, and efficient scoring techniques are used to reduce the variance. The resulting code is sufficiently fast and compact to be incorporated into iterative treatments of plasma dynamics requiring numerous neutral profiles. The calculation yields the neutral gas densities, pressures, fluxes, ionization rates, momentum transfer rates, energy transfer rates, and wall sputtering rates. Applications have included modeling of proposed INTOR/FED poloidal divertor designs and other experimental devices.
Download or read book Density Limit and Cross field Edge Transport Scaling in Alcator C Mod written by Brian LaBombard and published by . This book was released on 2002 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experiments in Alcator C-Mod have uncovered a direct link between the character and scaling of cross-field particle transport in the edge plasma and the density limit, nG. As ne/nG is increased from low values to values approaching [approx.] 1, an ordered progression in the cross-field edge transport physics occurs: first benign cross-field heat convection, then cross-field heat convection impacting the scrape-off layer (SOL) power loss channels and reducing the separatrix electron temperature, and finally 1bursty2 transport (normally associated with the far SOL) invading into closed flux surface regions and carrying a convective power loss that impacts the power balance of the discharge. These observations suggest that SOL transport and its scaling with plasma conditions plays a key role in setting the empirically observed density limit scaling law.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1994 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fusion Energy Update written by and published by . This book was released on 1986 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics of Plasma Wall Interactions in Controlled Fusion written by D. E. Post and published by Springer Science & Business Media. This book was released on 2013-11-21 with total page 1178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlled thermonuclear fusion is one of the possible candidates for long term energy sources which will be indispensable for our highly technological society. However, the physics and technology of controlled fusion are extremely complex and still require a great deal of research and development before fusion can be a practical energy source. For producing energy via controlled fusion a deuterium-tritium gas has to be heated to temperatures of a few 100 Million °c corres ponding to about 10 keV. For net energy gain, this hot plasma has to be confined at a certain density for a certain time One pro mising scheme to confine such a plasma is the use of i~tense mag netic fields. However, the plasma diffuses out of the confining magnetic surfaces and impinges on the surrounding vessel walls which isolate the plasma from the surrounding air. Because of this plasma wall interaction, particles from the plasma are lost to the walls by implantation and are partially reemitted into the plasma. In addition, wall atoms are released and can enter the plasma. These wall atoms or impurities can deteriorate the plasma performance due to enhanced energy losses through radiation and an increase of the required magnetic pressure or a dilution of the fuel in the plasma. Finally, the impact of the plasma and energy on the wall can modify and deteriorate the thermal and mechanical pro perties of the vessel walls.
Download or read book Transport Modeling of Edge Plasma in an M n written by R. Kanno and published by . This book was released on 2007 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings written by and published by . This book was released on 1987 with total page 862 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Plasma Boundary of Magnetic Fusion Devices written by P.C Stangeby and published by CRC Press. This book was released on 2000-01-01 with total page 738 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Plasma Boundary of Magnetic Fusion Devices introduces the physics of the plasma boundary region, including plasma-surface interactions, with an emphasis on those occurring in magnetically confined fusion plasmas. The book covers plasma-surface interaction, Debye sheaths, sputtering, scrape-off layers, plasma impurities, recycling and control, 1D and 2D fluid and kinetic modeling of particle transport, plasma properties at the edge, diverter and limiter physics, and control of the plasma boundary. Divided into three parts, the book begins with Part 1, an introduction to the plasma boundary. The derivations are heuristic and worked problems help crystallize physical intuition, which is emphasized throughout. Part 2 provides an introduction to methods of modeling the plasma edge region and for interpreting computer code results. Part 3 presents a collection of essays on currently active research hot topics. With an extensive bibliography and index, this book is an invaluable first port-of-call for researchers interested in plasma-surface interactions.
Download or read book Plasma Physics An Introductory Course written by R. O. Dendy and published by Cambridge University Press. This book was released on 1995-02-24 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: For the last thirty years, international summer schools in plasma physics have been held at Culham Laboratory, site of the Joint European Torus fusion project. This book has been developed from lectures given at these schools, and provides a wide-ranging introduction to the subject. The first few chapters deal with the fundamentals of plasma physics. In subsequent chapters, the applications and properties of man-made and naturally occurring plasmas are discussed. In addition, there are chapters devoted to general phenomena such as turbulence and chaos. The computational techniques employed in modelling plasma behaviour are also described. Since no prior knowledge of plasma physics is assumed, this book will act as an ideal introduction to the subject for final year undergraduates and beginning graduate students in physics, astronomy, mathematics and engineering.
