Pressure-driven Transport in the Core of Tokamak Plasmas PDF Download
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Author: Aaron John Redd
Publisher:
ISBN:
Category : Plasma instabilities
Languages : en
Pages : 506
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Book Description
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.
Author: Aaron John Redd
Publisher:
ISBN:
Category : Plasma instabilities
Languages : en
Pages : 506
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Book Description
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.
Author: John Rice
Publisher: Springer Nature
ISBN: 3030922669
Category : Science
Languages : en
Pages : 158
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Book Description
This book provides a comprehensive look at the state of the art of externally driven and self-generated rotation as well as momentum transport in tokamak plasmas. In addition to recent developments, the book includes a review of rotation measurement techniques, measurements of directly and indirectly driven rotation, momentum sinks, self-generated flow, and momentum transport. These results are presented alongside summaries of prevailing theory and are compared to predictions, bringing together both experimental and theoretical perspectives for a broad look at the field. Both researchers and graduate students in the field of plasma physics will find this book to be a useful reference. Although there is an emphasis on tokamaks, a number of the concepts are also relevant to other configurations.
Author: M. G. Bell
Publisher:
ISBN:
Category : Plasma confinement
Languages : en
Pages : 18
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Book Description
Author: Timothée Nicolas
Publisher:
ISBN:
Category :
Languages : en
Pages : 250
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Book Description
Author: Julien Medina
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
One of the most promising approach to controlled nuclear fusion is the tokamak. It is a toroidal machine confining a fusion plasma using magnetic fields. Transport of particles and heat, from the core toward the edges happens spontaneously, degrades the efficiency of the tokamak, and is driven by turbulence. We use a bounce-averaged 4D gyrokinetic code which solves the Vlasov-Quasi-neutrality system. The code is based on a reduced model which averages out the cyclotron and the bounce motion of the trapped particles to reduce the dimensionality. In this work we developed and tested a new module for the code, allowing to track test particle trajectories in phase space. As a first result obtained with test particles, we achieved to separate the diffusive contribution to the radial particle flux in energy space, from the non-diffusive contributions. Both fluxes present an intense peak indicating resonant particles dominate transport. On short period of time the test particles undergo a small scale advection, but on longer times, they follow a random walk process. We then explored with greater accuracy the fluxes in energy space. Furthermore we compared the obtained fluxes with quasi-linear predictions and found a qualitative agreement, although there was a ~50% discrepancy in the peak magnitude.
Author: R.B. White
Publisher: Elsevier
ISBN: 1483293262
Category : Science
Languages : en
Pages : 374
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Book Description
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.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309183197
Category : Science
Languages : en
Pages : 112
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Book Description
The purpose of this assessment of the fusion energy sciences program of the Department of Energy's (DOE's) Office of Science is to evaluate the quality of the research program and to provide guidance for the future program strategy aimed at strengthening the research component of the program. The committee focused its review of the fusion program on magnetic confinement, or magnetic fusion energy (MFE), and touched only briefly on inertial fusion energy (IFE), because MFE-relevant research accounts for roughly 95 percent of the funding in the Office of Science's fusion program. Unless otherwise noted, all references to fusion in this report should be assumed to refer to magnetic fusion. Fusion research carried out in the United States under the sponsorship of the Office of Fusion Energy Sciences (OFES) has made remarkable strides over the years and recently passed several important milestones. For example, weakly burning plasmas with temperatures greatly exceeding those on the surface of the Sun have been created and diagnosed. Significant progress has been made in understanding and controlling instabilities and turbulence in plasma fusion experiments, thereby facilitating improved plasma confinement-remotely controlling turbulence in a 100-million-degree medium is a premier scientific achievement by any measure. Theory and modeling are now able to provide useful insights into instabilities and to guide experiments. Experiments and associated diagnostics are now able to extract enough information about the processes occurring in high-temperature plasmas to guide further developments in theory and modeling. Many of the major experimental and theoretical tools that have been developed are now converging to produce a qualitative change in the program's approach to scientific discovery. The U.S. program has traditionally been an important source of innovation and discovery for the international fusion energy effort. The goal of understanding at a fundamental level the physical processes governing observed plasma behavior has been a distinguishing feature of the program.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 37
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Book Description
The long-range goal of the Numerical Tokamak Project (NTP) is the reliable prediction of tokamak performance using physics-based numerical tools describing tokamak physics. The NTP is accomplishing the development of the most advanced particle and extended fluid model's on massively parallel processing (MPP) environments as part of a multi-institutional, multi-disciplinary numerical study of tokamak core fluctuations. The NTP is a continuing focus of the Office of Fusion Energy's theory and computation program. Near-term HPCC work concentrates on developing a predictive numerical description of the core plasma transport in tokamaks driven by low-frequency collective fluctuations. This work addresses one of the greatest intellectual challenges to our understanding of the physics of tokamak performance and needs the most advanced computational resources to progress. We are conducting detailed comparisons of kinetic and fluid numerical models of tokamak turbulence. These comparisons are stimulating the improvement of each and the development of hybrid models which embody aspects of both. The combination of emerging massively parallel processing hardware and algorithmic improvements will result in an estimated 10**2--10**6 performance increase. Development of information processing and visualization tools is accelerating our comparison of computational models to one another, to experimental data, and to analytical theory, providing a bootstrap effect in our understanding of the target physics. The measure of success is the degree to which the experimentally observed scaling of fluctuation-driven transport may be predicted numerically. The NTP is advancing the HPCC Initiative through its state-of-the-art computational work. We are pushing the capability of high performance computing through our efforts which are strongly leveraged by OFE support.
Author: Federico David Halpern
Publisher:
ISBN: 9781109166835
Category :
Languages : en
Pages : 140
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Book Description
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.
