Download or read book ETUDE DU TRANSPORT DES IMPURETES DANS LES PLASMAS TOKAMAK written by Antoine Compant La Fontaine and published by . This book was released on 1984 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: LES MESURES D'EMISSIVITE DE RAIES (10 A 2000A) DES IMPURETES SONT UTILISEES DANS UN CODE DE TRANSPORT CALCULANT LES PROCESSUS ATOMIQUES ET LA DIFFUSION DES IMPURETES. LA DIFFUSION COLLISIONNELLE EST TROP FAIBLE POUR EXPLIQUER LE TRANSPORT OBSERVE. LE COEFFICIENT DE DIFFUSION ANORMAL DES IONS IMPURETES EST INVERSEMENT PROPORTIONNEL A LA MASSE DES IONS DE BASE (H**(+), D**(+), HE**(2+)). METHODE D'EXTRACTION D'UNE IMPURETE DONNEE DU PLASMA LORSQU'ON APPLIQUE UN CHAUFFAGE HF, DANS DES CONDITIONS DETERMINEES. ON ATTRIBUE LE TRANSPORT ANORMAL DES IMPURETES A L'INTERIEUR DE LA SURFACE Q=1 A UNE TURBULENCE Y APPARAISSANT PENDANT LES DISRUPTIONS INTERNES. A L'EXTERIEUR DE LA SURFACE Q=1, ON L'ATTRIBUE A LA MICROTURBULENCE. EN EXPRIMANT LA FONCTION DE LAGRANGE DU SYSTEME DE PARTICULES DANS UN CHAMP ELECTRIQUE TURBULENT, ON VERIFIE LA LOI D'ECHELLE EXPERIMENTALE D::(A)ALPHA MB**(-1)

Download or read book Etude Du Transport Turbulent Des Impuret s Dans Les Plasmas de Tokamak written by Shimpei Futatani and published by . This book was released on 2009 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this thesis is to understand impurity transport dynamics in the magnetically confined fusion plasmas. This includes the influence of the turbulent field which induces an anomalous transport in the plasma. Furthermore, this work demonstrates remarkable aspects for impurity transport in two different instabilities: ``ion temperature gradient (ITG) and trapped electron mode (TEM)''. It is shown that in presence of an internal transport barrier (ITB) created by a reversed magnetic shear configuration, one can obtain the reversal of impurity pinch velocity which can change from inward direction to outward direction. This scenario is favourable for expelling impurities from the central region and decontaminating the core plasma. The mechanism of pinch reversal is attributed to a change of direction of the curvature pinch and to a modification of the dominant underlying instability caused by a change of the gradient of the ion temperature which is a consequence of the ITB formation.

Download or read book Utilisation Du Rayonnement X mou Pour L tude Du Transport Des Impuret s Dans Les Plasmas de Tokamaks written by Axel Jardin and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Global energy consumption has increased significantly during the last century and will continue to grow in the coming decades. The development of sustainable energies alternative to fossil fuels is a crucial issue for the future generations. In this context, controlled thermonuclear fusion is a good candidate for the energy transition. Magnetic confinement fusion and tokamaks are currently the most promising solution to control the fusion reaction and use it for civil purposes.In tokamak plasmas, heavy impurities such as tungsten sputtered from plasma-facing components can migrate to the core plasma and strongly degrade fusion performance by radiation. The goal of this PhD thesis is to use this radiation in the soft X-ray range in order to obtain valuable information on tungsten transport in the core plasma. The final perspective is to control the impurity concentration and identify actuators that can act on this distribution.

Download or read book Impurity Transport in Tokamak Plasmas written by Peter Donnel and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Impurity transport is an issue of utmost importance for tokamaks. Indeed high-Z materials are only partially ionized in the plasma core, so that they can lead to prohibitive radiative losses even at low concentrations, and impact dramatically plasma performance and stability. On-axis accumulation of tungsten has been widely observed in tokamaks.While the very core impurity peaking is generally attributed to neoclassical effects, turbulent transport could well dominate in the gradient region at ITER relevant collisionality. Up to recently, first principles simulations of corresponding fluxes were performed with different dedicated codes, implicitly assuming that both transport channels are separable and therefore additive. The validity of this assumption is questionned. Simulations obtained with the gyrokinetic code GYSELA have shown clear evidences of a neoclassical-turbulence synergy for impurity transport and allowed the identification of a mechanism that underly this synergy.An analytical work allows to compute the level and the structure of the axisymmetric part of the electric potential knowing the turbulence intensity. Two mechanisms are found for the generation of poloidal asymmetries of the electric potential: flow compressibility and the ballooning of the turbulence. A new prediction for the neoclassical impurity flux in presence of large poloidal asymmetries and pressure anisotropies has been derived. A fair agreement has been found between the new theoretical prediction for neoclassical impurity flux and the results of a GYSELA simulation displaying large poloidal asymmetries and pressure anisotropies induced by the presence of turbulence.

Download or read book Theory of Tokamak Plasmas written by R.B. White and published by Elsevier. This book was released on 2017-01-31 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a graduate textbook on tokamak physics, designed to provide a basic introduction to plasma equilibrium, particle orbits, transport, and those ideal and resistive magnetohydrodynamic instabilities which dominate the behavior of a tokamak discharge, and to develop the mathematical methods necessary for their theoretical analysis.

Download or read book Collisional Transport of Trace Impurity Ions and the Role of the Radial Electric Field in Spherical Tokamak Plasmas written by Christopher G. Wrench and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The mitigation and control of impurities, or non-fuel ions, in tokamak plasmas is vital for reducing energy losses and an understanding of impurity transport is required in order to predict the performance of present and future tokamak devices. The development and application of a full orbit, test particle code to the study of the collisional transport of test impurity ions in spherical tokamak plasmas is presented. This code is tested against the standard analytic description of collisional transport in magnetised plasmas and is demonstrated to be particularly suited to the study of the tight aspect ratio of the spherical tokamak design. The principle results of the present work concern the investigation of the role of the radial electric field, a feature of high performance tokamak plasmas, on collisional ion transport. It is found that a static radial electric field leads to a significant reduction in the radial transport of test impurity ions. This effect may be explained in terms of a novel radial drift of the test ions arising due to the introduction of collisional Langevin terms to the full orbit, test particle equations of motion. This has significant implications for the confinement of impurity ions in high performance, steady state tokamak discharges. A scaling of this modification with impurity particle mass and charge numbers is derived analytically and verified numerically and a scaling with electric field parameters is derived numerically. A time dependent radial electric field, which models a number of transient events in tokamak plasmas such as the low- to high-mode transition and edge localised modes, is also investigated and attempts at a preliminary comparison between experimental and numerical observations of impurity transport in spherical tokamak devices is presented.

Download or read book Simulation of Inertial and Beam driven Effects on Impurities in Tokamak Plasmas written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments on beam-heated tokamak plasmas in the Impurity Study Experiment (ISX-B) indicate that counterinjection leads to enhanced accumulation of impurities and coinjection leads to reduced accumulation of impurities relative to ohmically heated plasmas. According to neoclassical theory, both inertial and beam-driven effects can modify impurity distributions in beam-heated plasmas. We have implemented treatments of these effects in our basic impurity transport simulation code, IMPTAR, in order to investigate whether these effects could account for the observations in ISX-B. We briefly review the neoclassical theory of these effects and infer various consequences. We then present simulation results for model coinjected and counterinjected ISX-B plasma with inertial and beam-driven effects treated both separately and together.

Download or read book Experimental Tests of Parallel Impurity Transport Theory in Tokamak Plasmas written by Matthew Logan Reinke and published by . This book was released on 2012 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: In realistic reactor scenarios, high temperature plasmas will be composed of not only the fusion reactants and products, but also impurities introduced purposefully or unintentionally from plasma facing materials. In tokamaks it is often assumed, sometimes erroneously, that surfaces of constant main ion pressure are also surfaces of constant impurity pressure. Although the same underlying physics determine impurity momentum balance along closed magnetic field lines, the increased mass and charge of high-Z impurities weights terms differently. Their large mass enhances inertial effects like the centrifugal force from toroidal rotation, and( can lead to accumulation of heavy impurities on the outboard side of a flux surface. Their high charge enhances ion-impurity friction and makes impurities sensitive to small poloidal variations in the electrostatic potential. In Alcator C-Mod, 2D (R,Z) measurements of photon emission from high-Z impurities reveal significant variations of impurity density on a flux surface. Poloidal variations, normalized to the flux surface average, I 2/(n ) , have been measured up to ~ 1/3, and separate cases of impurities accumulating on the inboard and outboard side of a flux surface are observed, depending on local plasmas conditions. Experiments demonstrate that these asymmetries are due to a combination of inertia., poloidal electric fields and ion-impurity friction, and measurements are compared to existing neoclassical parallel impurity transport theory. This is the first time centrifugal force has been observed to cause a substantial asymmetry in a plasma with no external momentum input and where the flow is entirely self-generated. Magnetically trapped fast ions, sustained by ion cyclotron waves, create a poloidally varying electrostatic potential which causes high-Z impurities to accumulate on the inboard side. Existing theory is extended to include this effect by incorporating a species that has an anisotropic pressure tensor. Experimental measurements in plasmas where the minority resonance layer is scanned show good qualitative and quantitative agreement with this extended theory. The sensitivity of 51/(nz) to fast-ions demonstrates the opportunity for the impurity asymmetry to be used as a novel diagnostic tool and calls into question prior work on in/out asymmetries in neutral beam heated plasmas. /down asymmetries in the banana regime are unable to be explained by ion/impurity friction in the trace limit, nZZ 2 /n

Download or read book Test of Local Transport Theory and Reduced Wall Impurity Influx with Highly Radiative Plasmas in the Tokamak Fusion Test Reactor written by K. W. Hill and published by . This book was released on 1998 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of High impurity Accumulation and Transport in the JET Tokamak Plasmas from Soft X ray Tomography written by Michele Romanelli and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rotation and Impurity Transport in a Tokamak Plasma with Directed Neutral Beam Injection written by Weston M. Stacey and published by . This book was released on 1984 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rotation and Impurity Transport in a Tokamak Plasma with Directed Neutral Beam Injection written by W. M. Stacey (Jr) and published by . This book was released on 1984 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impurity Transport Studies in Tokamak Edge Plasmas Using Visibe Imaging written by Sanjay Gangadhara and published by . This book was released on 2001 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding impurity transport in the scrape-off layer (SOL) of tokamak plasmas is a necessary piece of developing the physics basis for designing next-generation reactors. A system for inferring impurity transport parallel and perpendicular to local magnetic field lines has been developed on Alcator C-Mod using gas-injection "plumes". In this system, impurity gas is injected at a fixed position in the SOL via a reciprocating fast-scanning probe, and the resulting emission is imaged. In this paper visible light emission patterns from C+1 and C+2 ions are presented.

Download or read book Neoclassical Transport of Impurtities in Tokamak Plasmas written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tokamak plasmas are inherently comprised of multiple ion species. This is due to wall-bred impurities and, in future reactors, will result from fusion-born alpha particles. Relatively small concentrations of highly charged non-hydrogenic impurities can strongly influence plasma transport properties whenever n/sub I/e/sub I//sup 2//n/sub H/e/sup 2/ greater than or equal to (m/sub e//m/sub H/)/sup 1/2/. The determination of the complete neoclassical Onsager matrix for a toroidally confined multispecies plasma, which provides the linear relation between the surface averaged radial fluxes and the thermodynamic forces (i.e., gradients of density and temperature, and the parallel electric field), is reviewed. A closed set of one-dimensional moment equations is presented for the time evolution of thermodynamic and magnetic field quantities which results from collisional transport of the plasma and two dimensional motion of the magnetic flux surface geometry. The effects of neutral beam injection on the equilibrium and transport properties of a toroidal plasma are consistently included.

Download or read book Experimental Inference of Particle Transport in Tokamak Plasmas written by Francesco Sciortino and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a whole, this work provides one of the highest-fidelity assessments of cross-field impurity transport in tokamaks, offering the means to extend comparisons between theory and experiments in the particle transport channel.

Download or read book Numerical Treatment of the Problem of Impurity Transport in Tokamak Plasma written by F. Spineanu and published by . This book was released on 1984 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of the Mutual Dependence Between Lower Hybrid Current Drive and Heavy Impurity Transport in Tokamak Plasma written by Axel Jardin and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: