Experimental Measurements of Energy Transport in Tokamak Plasmas

Experimental Measurements of Energy Transport in Tokamak Plasmas PDF Author: Dmitry Meyerson
Publisher:
ISBN:
Category :
Languages : en
Pages : 72

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Book Description
A tokamak plasma near equilibrium can be perturbed with modulated power sources, such as modulated electron cyclotron heating, or repeated cold pulse application. Temperature response to cyclical changes in profiles parameters that are induced by modulated power deposition can be used to test theoretical transport models as well as improve experimental phenomenology used to optimize tokamak performance. The goal of this document to discuss some methods of analyzing electron temperature data in the context of energy transport. Specific experiments are considered in order to demonstrate the methods discussed, as well as to examine the electron energy transport properties of these shots. Electron cyclotron emission provides a convenient way to probe electron temperature for plasmas in thermal equilibrium. We can show that in tokamak devices, barring harmonic overlap, we can associate a particular frequency with a particular location in a tokamak, by carefully selecting the detection frequency and line of sight of the responsible antenna. ECE radiometers typically measure temperature at tens of locations at a time with a spatial resolution on the order of a few centimeters. Tracking the evolution of electron energy flux depends on careful analysis of the resulting data. The most straightforward way to analyze temperature perturbations is to simply consider various harmonics of the driving source and consider the corresponding harmonics in the temperature. We can analyze the phase and amplitude of the response to find the effective phase velocity of the perturbation which can in turn be related to parameters in the selected heat flux model. The most common example is to determine, the diffusion coefficient that appears in the linearized energy transport equation. The advantages and limitation of this method will be discussed in detail in Section 3. A more involved approach involves using the perturbed temperature data to compute modulated heat flux at any given point in the perturbation cycle, rather than using the temperature data directly. As before the heat flux can then be related to measured profile parameters and theoretical predictions. The advantages and limitations of this approach will be discussed in more detail. Both of the mentioned analysis methods are used to probe electron energy transport in a quiescent H mode (QH mode) shot conducted at DIIID. The nature of the internal transport barrier that is present in the shot is considered in light of the results.

Experimental Measurements of Energy Transport in Tokamak Plasmas

Experimental Measurements of Energy Transport in Tokamak Plasmas PDF Author: Dmitry Meyerson
Publisher:
ISBN:
Category :
Languages : en
Pages : 72

Get Book Here

Book Description
A tokamak plasma near equilibrium can be perturbed with modulated power sources, such as modulated electron cyclotron heating, or repeated cold pulse application. Temperature response to cyclical changes in profiles parameters that are induced by modulated power deposition can be used to test theoretical transport models as well as improve experimental phenomenology used to optimize tokamak performance. The goal of this document to discuss some methods of analyzing electron temperature data in the context of energy transport. Specific experiments are considered in order to demonstrate the methods discussed, as well as to examine the electron energy transport properties of these shots. Electron cyclotron emission provides a convenient way to probe electron temperature for plasmas in thermal equilibrium. We can show that in tokamak devices, barring harmonic overlap, we can associate a particular frequency with a particular location in a tokamak, by carefully selecting the detection frequency and line of sight of the responsible antenna. ECE radiometers typically measure temperature at tens of locations at a time with a spatial resolution on the order of a few centimeters. Tracking the evolution of electron energy flux depends on careful analysis of the resulting data. The most straightforward way to analyze temperature perturbations is to simply consider various harmonics of the driving source and consider the corresponding harmonics in the temperature. We can analyze the phase and amplitude of the response to find the effective phase velocity of the perturbation which can in turn be related to parameters in the selected heat flux model. The most common example is to determine, the diffusion coefficient that appears in the linearized energy transport equation. The advantages and limitation of this method will be discussed in detail in Section 3. A more involved approach involves using the perturbed temperature data to compute modulated heat flux at any given point in the perturbation cycle, rather than using the temperature data directly. As before the heat flux can then be related to measured profile parameters and theoretical predictions. The advantages and limitations of this approach will be discussed in more detail. Both of the mentioned analysis methods are used to probe electron energy transport in a quiescent H mode (QH mode) shot conducted at DIIID. The nature of the internal transport barrier that is present in the shot is considered in light of the results.

Experimental Determination of the Dimensionless Scaling Parameter of Energy Transport in Tokamaks

Experimental Determination of the Dimensionless Scaling Parameter of Energy Transport in Tokamaks PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 4

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Book Description
Controlled fusion experiments have focused on the variation of the plasma characteristics as the engineering or control parameters are systematically changed. This has led to the development of extrapolation formulae for prediction of future device performance using these same variables as a basis. Recently, it was noticed that present-day tokamaks can operate with all of the dimensionless variables which appear in the Vlasov-Maxwell system of equations at values projected for a fusion powerplant with the exception of the parameter [rho]{sub *}, the gyroradius normalized to the machine size. The scaling with this parameter is related to the benefit of increasing the size of the machine either directly or effectively by increasing the magnetic field. It is exactly this scaling which is subject to systematic error in the inter-machine databases and the cost driver for any future machine. If this scaling can be fixed by a series of single machine experiments, much as the current and power scalings have been, the confidence in the prediction of future device performance would be greatly enhanced. While carrying out experiments of this type, it was also found that the [rho]{sub *} scaling can illuminate the underlying physics of energy transport. Conclusions drawn from experiments on the DIII-D tokamak in these two areas are the subject of this paper.

Driven Rotation, Self-Generated Flow, and Momentum Transport in Tokamak Plasmas

Driven Rotation, Self-Generated Flow, and Momentum Transport in Tokamak Plasmas PDF 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.

Experimental Measurement of Nonlinear Energy Transfer on the Tokamak Fusion Test Reactor

Experimental Measurement of Nonlinear Energy Transfer on the Tokamak Fusion Test Reactor PDF Author: Chi-su Kim
Publisher:
ISBN:
Category :
Languages : en
Pages : 230

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Book Description


Energetic Particles in Tokamak Plasmas

Energetic Particles in Tokamak Plasmas PDF Author: Sergei Sharapov
Publisher: CRC Press
ISBN: 1351002813
Category : Science
Languages : en
Pages : 156

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Book Description
The study of energetic particles in magnetic fusion plasmas is key to the development of next-generation "burning" plasma fusion experiments, such as the International Thermonuclear Experimental Reactor (ITER) and the Demonstration Power Station (DEMO). This book provides a comprehensive introduction and analysis of the experimental data on how fast ions behave in fusion-grade plasmas, featuring the latest ground-breaking results from world-leading machines such as the Joint European Torus (JET) and the Mega Ampere Spherical Tokamak (MAST). It also details Alfvenic instabilities, driven by energetic ions, which can cause enhanced transport of energetic ions. MHD spectroscopy of plasma via observed Alfvenic waves called "Alfvén spectroscopy" is introduced and several applications are presented. This book will be of interest to graduate students, researchers, and academics studying fusion plasma physics. Features: Provides a comprehensive overview of the field in one cohesive text, with the main physics phenomena explained qualitatively first. Authored by an authority in the field, who draws on his extensive experience of working with energetic particles in tokamak plasmas. Is suitable for extrapolating energetic particle phenomena in fusion to other plasma types, such as solar and space plasmas.

Texas Experimental Tokamak, a Plasma Research Facility

Texas Experimental Tokamak, a Plasma Research Facility PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 82

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Book Description
In the year just past, the authors made major progress in understanding turbulence and transport in both core and edge. Development of the capability for turbulence measurements throughout the poloidal cross section and intelligent consideration of the observed asymmetries, played a critical role in this work. In their confinement studies, a limited plasma with strong, H-mode-like characteristics serendipitously appeared and received extensive study though a diverted H-mode remains elusive. In the plasma edge, they appear to be close to isolating a turbulence drive mechanism. These are major advances of benefit to the community at large, and they followed from incremental improvements in diagnostics, in the interpretation of the diagnostics, and in TEXT itself. Their general philosophy is that the understanding of plasma physics must be part of any intelligent fusion program, and that basic experimental research is the most important part of any such program. The work here demonstrates a continuing dedication to the problems of plasma transport which continue to plague the community and are an impediment to the design of future devices. They expect to show here that they approach this problem consistently, systematically, and effectively.

Cross-field Particle Transport in the Edge of Plasma of Tokamak Experiments and Implications for ITER

Cross-field Particle Transport in the Edge of Plasma of Tokamak Experiments and Implications for ITER PDF Author: Brian LaBombard
Publisher:
ISBN:
Category :
Languages : en
Pages : 20

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Book Description
Particle transport in the edge plasma and scrape-off layer will play a key role in the performance and operation of a tokamak fusion reactor: setting the width of the scrape-off layer density profile and its impurity screening characteristics, regulating the energetic particle fluxes onto first-wall components and associated impurity generation rates, and determining the effectiveness of the divertor in receiving particle exhaust and controlling neutral pressures in the main-chamber. The processes which govern particle transport involve plasma turbulence, phenomena which can not yet be reliably computed from a first-principles numerical simulation. Thus, in order to project to a reactor-scale experiment, such as ITER, one must first develop an understanding of particle transport phenomena based on experimental measurements in existing plasma fusion devices. Over the past few years of research, a number of fundamental advances in the understanding of the cross-field particle transport physics have occurred, replacing crude, incorrect, and often misleading transport models such as the "constant diffusion coefficient" model with a more appropriate description of the phenomenon. It should be noted that this description applies to transport processes in the absence of ELM phenomenon, i.e., physics underlying the "background" plasma state. In this letter, we first review the experimental support for this understanding which is based extensively on data from L-mode discharges and from H-mode discharges at time intervals without ELMs. We then comment on its implications for ITER.

Tokamaks

Tokamaks PDF Author: John Wesson
Publisher: Oxford University Press
ISBN: 0199592233
Category : Science
Languages : en
Pages : 828

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Book Description
The tokamak is the principal tool in controlled fusion research. This book acts as an introduction to the subject and a basic reference for theory, definitions, equations, and experimental results. The fourth edition has been completely revised, describing their development of tokamaks to the point of producing significant fusion power.

Experimental Inference of Particle Transport in Tokamak Plasmas

Experimental Inference of Particle Transport in Tokamak Plasmas PDF Author: Francesco Sciortino
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
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.

Turbulence and Transport Measurements in Alcator C-Mod and Comparisons with Gyrokinetic Simulations

Turbulence and Transport Measurements in Alcator C-Mod and Comparisons with Gyrokinetic Simulations PDF Author: Paul Chappell Ennever
Publisher:
ISBN:
Category :
Languages : en
Pages : 139

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Book Description
Turbulence in tokamak plasmas is the primary means by which energy is transported from the core of the plasma to the edge, where it is lost, and is therefore the main limitation of tokamak plasma performance. Dilution of the main-ion species was found to have a stabilizing effect on ion gyroradius scale turbulence in tokamak plasmas. Dilution of deuterium tokamak plasmas is the reduction of the ratio of the deuterium ion density to the electron density, nD=ne, to less than 1.0 through the introduction of low-Z impurity species into the plasma. Controlled dilution experiments were performed on Alcator C-Mod wherein plasmas at a range of electron density and plasma current were seeded with nitrogen while a cryopump held the electron density fixed. The electron density fluctuations due to turbulence were monitored using a phase contrast imaging (PCI) diagnostic, an absolutely calibrated diagnostic that measures the line-integral of the electron density fluctuations along 32 vertical chords. In these experiments the seeding reduced the PCI density fluctuations, and had a stabilizing effect on the ion energy transport. The seeding also reversed the direction of intrinsic rotation in certain cases. Nonlinear simulations using the gyrokinetic turbulence code GYRO were performed using measured kinetic profiles from the dilution experiments both before and after the nitrogen seeding. The GYRO simulations reproduced the observed reduction in the turbulent ion energy transport with the nitrogen seeding. The GYRO simulated turbulent density fluctuations were compared to the PCI measurements using a synthetic diagnostic, and they were found to be consistent. GYRO simulations were also performed varying only the main ion dilution to explore the theoretical effects of the dilution on energy transport. Through this it was found that the dilution reduced the turbulent ion energy transport in a wide variety of cases, but primarily increased the critical gradient at low densities, and primarily reduced the stiffness of the transport at high densities. This dilution effect is related to observations of reductions in energy transport from seeding on other tokamaks, and will likely have an impact on ITER and future fusion reactors.