Experimental Measurements Of Energy Transport In Tokamak Plasmas
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| Author | : Dmitry Meyerson |
| Publisher | : |
| Total Pages | : 72 |
| Release | : 2010 |
| Genre | : |
| ISBN | : |
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.
| Author | : |
| Publisher | : |
| Total Pages | : 4 |
| Release | : 1995 |
| Genre | : |
| ISBN | : |
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.
| Author | : John Rice |
| Publisher | : Springer Nature |
| Total Pages | : 158 |
| Release | : 2022-01-13 |
| Genre | : Science |
| ISBN | : 3030922669 |
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 | : Chi-su Kim |
| Publisher | : |
| Total Pages | : 230 |
| Release | : 1996 |
| Genre | : |
| ISBN | : |
| Author | : Sergei Sharapov |
| Publisher | : CRC Press |
| Total Pages | : 156 |
| Release | : 2021-04-02 |
| Genre | : Science |
| ISBN | : 1351002813 |
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.
| Author | : |
| Publisher | : |
| Total Pages | : 82 |
| Release | : 1995 |
| Genre | : |
| ISBN | : |
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.
| Author | : D. E. Post |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 1178 |
| Release | : 2013-11-21 |
| Genre | : Science |
| ISBN | : 1475700679 |
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.
| Author | : Brian LaBombard |
| Publisher | : |
| Total Pages | : 20 |
| Release | : 2003 |
| Genre | : |
| ISBN | : |
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.
| Author | : National Research Council |
| Publisher | : National Academies Press |
| Total Pages | : 112 |
| Release | : 2001-05-07 |
| Genre | : Science |
| ISBN | : 0309183197 |
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 | : Francesco Sciortino |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2021 |
| Genre | : |
| ISBN | : |
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.
