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Anomalous Transport Modelling Of Tokamak Plasmas
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Book Synopsis Anomalous Transport Modelling of Tokamak Plasmas by :
Download or read book Anomalous Transport Modelling of Tokamak Plasmas written by and published by . This book was released on 1992 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theory based transport simulations of DIII-D, JET, ITER are compared to experimental data using a combination of anamolous transport models. The Multiple-mode Transport Model is calibrated to a give set of L-mode and H-mode discharges with an emphasis on testing the adequacy of anomalous flux contributions from drift/[eta][sub i] and resistive ballooning mode theories. A survey of possible additions and/or alternatives to the model from recent theories on neoclassical MHD effects, hot ion modes, circulating electron modes, and high-m tearing modes is also included.
Book Synopsis Aspects of Anomalous Transport in Plasmas by : Radu Balescu
Download or read book Aspects of Anomalous Transport in Plasmas written by Radu Balescu and published by CRC Press. This book was released on 2005-04-01 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anomalous transport is a ubiquitous phenomenon in astrophysical, geophysical and laboratory plasmas; and is a key topic in controlled nuclear fusion research. Despite its fundamental importance and ongoing research interest, a full understanding of anomalous transport in plasmas is still incomplete, due to the complexity of the nonlinear phenomena involved. Aspects in Anomalous Transport in Plasmas is the first book to systematically consider anomalous plasma transport theory and provides a unification of the many theoretical models by emphasizing interrelations between seemingly different methodologies. It is not intended as a catalogue of the vast number of plasma instabilities leading to anomalous transport; instead it chooses a number of these and emphasizes the aspects specifically due to turbulence. After a brief introduction, the microscopic theory of turbulence is discussed, including quasilinear theory and various aspects of renormalization methods, which leads to an understanding of resonance broadening, mode coupling, trajectory correlation and clumps. The second half of the book is devoted to stochiastic tramsport, using methods based on the Langevin equations and on Random Walk theory. This treatment aims at going beyond the traditional limits of weak turbulence, by introducing the recently developed method of decorrelation trajectories, and its application to electrostatic turbulence, magnetic turbulence and zonal flow generation. The final chapter includes very recent work on the nonlocal transport phenomenon.
Book Synopsis Integrated Model for Transport and Large Scale Instabilities in Tokamak Plasmas by : Federico David Halpern
Download or read book Integrated Model for Transport and Large Scale Instabilities in Tokamak Plasmas written by Federico David Halpern and published by . This book was released on 2009 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved models for neoclassical tearing modes and anomalous transport are developed and validated within integrated modeling codes to predict toroidal rotation, temperature and current density profiles in tokamak plasmas. Neoclassical tearing modes produce helical filaments of plasma, called magnetic islands, which have the effect of degrading tokamak plasma confinement or terminating the discharge. An improved code is developed in order to compute the widths of multiple simultaneous magnetic islands whose shapes are distorted by the radial variation in the magnetic perturbation [F. D. Halpern, et al., J. Plasma Physics 72 (2006) 1153]. It is found in simulations of DIII-D and JET tokamak discharges that multiple simultaneous magnetic islands produce a 10% to 20% reduction in plasma thermal confinement. If magnetic islands are allowed to grow to their full width in ITER fusion reactor simulations, fusion power production is reduced by a factor of four [F. D. Halpern, et al., Phys. Plasmas 13 (2006) 062510]. In addition to improving the prediction of neoclassical tearing modes, a new Multi-Mode transport model, MMM08, was developed to predict temperature and toroidal angular frequency profiles in simulations of tokamak discharges. The capability for predicting toroidal rotation is motivated by ITER simulation results that indicate that the effects of toroidal rotation can increase ITER fusion power production [F. D. Halpern et al., Phys. Plasmas 15 (2008), 062505]. The MMM08 model consists of an improved model for transport driven by ion drift modes [F. D. Halpern et al., Phys. Plasmas 15 (2008) 012304] together with a model for transport driven by short wavelength electron drift modes combined with models for transport driven by classical processes. The new MMM08 transport model was validated by comparing predictive simulation results with experimental data for 32 discharges in the DIII-D and JET tokamaks. It was found that the prediction of intrinsic plasma rotation is consistent with experimental measurements in discharges with zero net torque. A scaling relation was developed for the toroidal momentum confinement time (angular momentum divided by net torque) as a function of plasma current and torque per ion.
Book Synopsis Transport Analysis in Tokamak Plasmas by : Sara Moradi
Download or read book Transport Analysis in Tokamak Plasmas written by Sara Moradi and published by LAP Lambert Academic Publishing. This book was released on 2010-08 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the least understood areas of the plasma particle or heat transport is the turbulent transport. In this work the main focus is on the development and data analysis of anomalous transport characteristics (transport coefficients and fluxes) under fusion conditions in large tokamaks. Fluid and gyro-kinetic models are used and obtained results are compared. A model based on fractional kinetics for the study of the SOL turbulent transport characteristics, where non-Gaussian PDFs are observed, is developed.
Book Synopsis Pressure-driven Transport in the Core of Tokamak Plasmas by : Aaron John Redd
Download or read book Pressure-driven Transport in the Core of Tokamak Plasmas written by Aaron John Redd and published by . This book was released on 1998 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is experimental and theoretical evidence of anomalous transport near the magnetic axis in tokamak plasmas, a region in which drift modes are linearly stable. Experimental evidence suggests that this additional transport is strongly affected by the plasma geometry (i.e., elongation and triangularity), more so than drift modes[1]. The finite-beta kinetic ballooning instability is predicted to exist close to the magnetic axis and is strongly affected by the plasma geometry. In this study, we explore the properties of the kinetic ballooning mode with the comprehensive electromagnetic kinetic stability calculations of the FULL code. Using FULL, we quantify the parametric dependence of kinetic ballooning transport on various plasma parameters, including the flux-surface elongation and triangularity, the normalized pressure beta and the flux-surface inverse aspect ratio. Based on these stability calculations, an algebraic kinetic ballooning transport model is developed. Also included in this dissertation are two independent studies of transport in tokamak plasmas, carried out with the BALDUR predictive transport code. In the first study, the sensitivity of these transport simulations to boundary and initial conditions is examined. In the second, a transport model developed by Ottaviani, Horton and Erba (OHE) is incorporated into the BALDUR code, and the density and temperature profiles predicted by this model are compared to experiment for a series of experimental discharges.
Book Synopsis Observations of Anomalous Transport in Tokamak Plasmas with No Momentum Input by : William Davis Lee
Download or read book Observations of Anomalous Transport in Tokamak Plasmas with No Momentum Input written by William Davis Lee and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas. The time evolution of core impurity toroidal rotation velocity profiles has been measured with a crystal x-ray spectrometer array. Following the L-mode to EDA (enhanced D[/sub/ alpha]) H-mode transition in both Ohmic and ICRF heated discharges, the ensuing co-current toroidal rotation velocity, which is generated in the absence of any external momentum source, is observed to propagate in from the edge plasma to the core with a time scale of order of the observed energy confinement time, but much less than the neo-classical momentum confinement time. The steady state toroidal rotation velocity profiles in EDA H-mode plasmas are relatively flat and the momentum transport can be simulated with a simple diffusion model. Assuming the L-H transition produces an instantaneous edge velocity source (which disappears at the H- to L-mode transition), the momentum transport may be characterized by a diffusivity, with values of 0.07 m2/s during EDA H-mode and 0.2 m2/s in L-mode. These values are large compared to the calculated neo-classical momentum diffusivities. Velocity profiles during ELM-free H-modes are centrally peaked, which suggests inward momentum convection; the observed profiles are matched with simulations including an inward convection velocity of 10 m/s. In EDA H-mode discharges which develop internal transport barriers, the velocity profiles become hollow in the center indicating the presence of a negative radial electric field well in the vicinity of the barrier foot.
Book Synopsis Multi-fluid Code Simulations Including Anomalous Non-diffusive Transport of Plasma and Impurities in the Tokamak SOL. by :
Download or read book Multi-fluid Code Simulations Including Anomalous Non-diffusive Transport of Plasma and Impurities in the Tokamak SOL. written by and published by . This book was released on 2003 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fast intermittent transport has been observed in the scrape-off layer (SOL) of major tokamaks including Alcator C-Mod, DIII-D, and NSTX. This kind of transport is not diffusive but rather convective. It strongly increases plasma flux to the chamber walls and enhances the recycling of neutral particles in the main chamber. We discuss anomalous cross-field convection (ACFC) model for impurity and main plasma ions and its relation to intermittent transport events, i.e. plasma density blobs and holes in the SOL. Along with plasma diffusivity coefficients, our transport model introduces time-independent anomalous cross-field convective velocity. In the discharge modelling, diffusivity coefficients and ACFC velocity profiles are adjusted to match a set of representative experimental data. We use this model in the edge plasma physics code UEDGE to simulate the multi-fluid two-dimensional transport for these three tokamaks. We present simulation results suggesting the dominance of anomalous convection in the far SOL transport. These results are consistent with the hypothesis that the chamber wall is an important source of impurities and that different impurity charge states have different directions of anomalous convective velocity.
Book Synopsis Modeling the Anomalous Heat Transport in a Tokamak Plasma by :
Download or read book Modeling the Anomalous Heat Transport in a Tokamak Plasma written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main problems in fusion research is the understanding of the dynamics governing the heat transport in a tokamak plasma. Because of unexpectedly large transport coefficients observed in experiments the transport is called "anomalous". This property is one of the main reasons why there is no energy produced by fusion yet. Mathematically, the anomalous heat transport problem is modelled by a non-standard heat equation, with a heat conductivity coefficient depending on the gradient of the solution in a piecewise differentiable way with a jump discontinuity. In order to detect precisely the region where the anomalous transport starts playing a role, we develop an explicit front tracking technique. The differential equation is split at the discontinuity points (front points) into sub-problems. We prove that each of the problems can be treated separately and that their solutions match continuously at the inner boundary. To find the position of the inner boundary (the front point), we solve an additional ordinary differential equation. Numerically, we use the finite element method for the space discretization. For the time discretization, we apply a newly developed algorithm. It is based on the trapezoidal rule, but uses the defect of the 4th order Lobatto III A scheme for optimization of the number of the Newton iterations, adaptation of the time step and estimation of the local and global errors. The numerical capabilities of the algorithm are demonstrated on several numerical examples. The anomalous transport problem is solved and the parameter space is explored. The high accuracy of the algorithm is shown comparing the numerical and analytical results at the stationary state. Moreover, the treatment of multiple front points, which correspond to turbulence regime in the heat transport, is performed.
Book Synopsis Anomalous Transport and Confinement Scaling Studies in Tokamaks by :
Download or read book Anomalous Transport and Confinement Scaling Studies in Tokamaks written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In addressing the general issue of anomalous energy transport, this paper reports on results of theoretical studies concerning: (1) the characteristics and relative strength of the dominant kinetic instabilities likely to be present under realistic tokamak operating conditions; (2) specific nonlinear processes relevant to the saturation and transport properties of drift-type instabilities; (3) the construction of semiempirical models for electron thermal transport and the scaling trends inferred from them; and (4) the application of specific anomalous transport models to simulate recent large-scale confinement experiments (TFTR and JET) and current drive experiments.
Book Synopsis Mathematical Modeling Plasma Transport in Tokamaks by :
Download or read book Mathematical Modeling Plasma Transport in Tokamaks written by and published by . This book was released on 1995 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, the author applied a systematic calibration, validation and application procedure based on the methodology of mathematical modeling to international thermonuclear experimental reactor (ITER) ignition studies. The multi-mode plasma transport model used here includes a linear combination of drift wave branch and ballooning branch instabilities with two a priori uncertain constants to account for anomalous plasma transport in tokamaks. A Bayesian parameter estimation method is used including experimental calibration error/model offsets and error bar rescaling factors to determine the two uncertain constants in the transport model with quantitative confidence level estimates for the calibrated parameters, which gives two saturation levels of instabilities. This method is first tested using a gyroBohm multi-mode transport model with a pair of DIII-D discharge experimental data, and then applied to calibrating a nominal multi-mode transport model against a broad database using twelve discharges from seven different tokamaks. The calibrated transport model is then validated on five discharges from JT-60 with no adjustable constants. The results are in a good agreement with experimental data. Finally, the resulting class of multi-mode tokamak plasma transport models is applied to the transport analysis of the ignition probability in a next generation machine, ITER. A reference simulation of basic ITER engineering design activity (EDA) parameters shows that a self-sustained thermonuclear burn with 1.5 GW output power can be achieved provided that impurity control makes radiative losses sufficiently small at an average plasma density of 1.2 X 102°/m3 with 50 MW auxiliary heating. The ignition probability of ITER for the EDA parameters, can be formally as high as 99.9% in the present context. The same probability for concept design activity (CDA) parameters of ITER, which has smaller size and lower current, is only 62.6%.
Book Synopsis Models of Coupled Transport to Investigate Anomalous Transport in Tokamaks by : Renato Gatto
Download or read book Models of Coupled Transport to Investigate Anomalous Transport in Tokamaks written by Renato Gatto and published by . This book was released on 1996 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Microinstability-based Model for Anomalous Thermal Confinement in Tokamaks by :
Download or read book Microinstability-based Model for Anomalous Thermal Confinement in Tokamaks written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper deals with the formulation of microinstability-based thermal transport coefficients (chi/sub j/) for the purpose of modelling anomalous energy confinement properties in tokamak plasmas. Attention is primarily focused on ohmically heated discharges and the associated anomalous electron thermal transport. An appropriate expression for chi/sub e/ is developed which is consistent with reasonable global constraints on the current and electron temperature profiles as well as with the key properties of the kinetic instabilities most likely to be present. Comparisons of confinement scaling trends predicted by this model with the empirical ohmic data base indicate quite favorable agreement. The subject of anomalous ion thermal transport and its implications for high density ohmic discharges and for auxiliary-heated plasmas is also addressed.
Book Synopsis Oeuvres de M. de Voltaire. Essai sur les moeurs et l'esprit des nations [Siècle de Louis XIV et de Louis XV]. by :
Download or read book Oeuvres de M. de Voltaire. Essai sur les moeurs et l'esprit des nations [Siècle de Louis XIV et de Louis XV]. written by and published by . This book was released on 1771 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Anomalous Diffusion and Transport Beta Limits in Dense Tokamak Plasmas by : Ronald D. Stambaugh
Download or read book Anomalous Diffusion and Transport Beta Limits in Dense Tokamak Plasmas written by Ronald D. Stambaugh and published by . This book was released on 1977 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis TEMPEST Simulations of the Plasma Transport in a Single-Null Tokamak Geometry by :
Download or read book TEMPEST Simulations of the Plasma Transport in a Single-Null Tokamak Geometry written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present edge kinetic ion transport simulations of tokamak plasmas in magnetic divertor geometry using the fully nonlinear (full-f) continuum code TEMPEST. Besides neoclassical transport, a term for divergence of anomalous kinetic radial flux is added to mock up the effect of turbulent transport. In order to study the relative roles of neoclassical and anomalous transport, TEMPEST simulations were carried out for plasma transport and flow dynamics in a single-null tokamak geometry, including the pedestal region that extends across the separatrix into the scrape-off layer and private flux region. In a series of TEMPEST simulations were conducted to investigate the transition of midplane pedestal heat flux and flow from the neoclassical to the turbulent limit and the transition of divertor heat flux and flow from the kinetic to the fluid regime via an anomalous transport scan and a density scan. The TEMPEST simulation results demonstrate that turbulent transport (as modelled by large diffusion) plays a similar role to collisional decorrelation of particle orbits and that the large turbulent transport (large diffusion) leads to an apparent Maxwellianization of the particle distribution. Moreover, we show the transition of parallel heat flux and flow at the entrance to the divertor plates from the fluid to the kinetic regime. For an absorbing divertor plate boundary condition, a non-half-Maxwellian is found due to the balance between upstream radial anomalous transport and energetic ion endloss.
Book Synopsis Anomalous Radial Transport in Tokamak Edge Plasma by : Vasudeva Raghavendra Kowsik Bodi
Download or read book Anomalous Radial Transport in Tokamak Edge Plasma written by Vasudeva Raghavendra Kowsik Bodi and published by . This book was released on 2010 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy from nuclear fusion of Hydrogen isotopes is a possible alternative to fossil fuels. For this to be of practical utility, confinement of Hydrogen in a plasma state for a minimum duration is necessary. Since confinement is strongly affected by radial transport processes, understanding the observed modes of radial transport in confined plasma is of vital importance for progress towards fusion energy. The present dissertation is aimed at studying radial (cross-field) transport in the tokamak edge plasma. The present thesis is divided into three parts : In the first part, we present a model of generation of intermittent convective meso-scale structures (blobs) based on the synergy of the interchange drive and nonlinear effects associated with drift-wave turbulence. In the second part, we attempt to explain the preferential propagation of blobs radially outward as a consequence of the radially decreasing density of a confined plasma. In the third part, we present a model for simulating anomalous radial transport in kinetic codes for tokamak edge plasma.
Book Synopsis Anomalous Transport: Applications, Mathematical Perspectives, and Big Data by : Ralf Metzler
Download or read book Anomalous Transport: Applications, Mathematical Perspectives, and Big Data written by Ralf Metzler and published by Frontiers Media SA. This book was released on 2021-01-08 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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