Download or read book Experimental Measurements of Energy Transport in Tokamak Plasmas written by Dmitry Meyerson and published by . This book was released on 2010 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Experimental Determination of the Dimensionless Scaling Parameter of Energy Transport in Tokamaks written by and published by . This book was released on 1995 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Driven Rotation Self Generated Flow and Momentum Transport in Tokamak Plasmas written by John Rice and published by Springer Nature. This book was released on 2022-01-13 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Experimental Measurement of Nonlinear Energy Transfer on the Tokamak Fusion Test Reactor written by Chi-su Kim and published by . This book was released on 1996 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energetic Particles in Tokamak Plasmas written by Sergei Sharapov and published by CRC Press. This book was released on 2021-04-02 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Texas Experimental Tokamak a Plasma Research Facility written by and published by . This book was released on 1995 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Physics of Plasma Wall Interactions in Controlled Fusion written by D. E. Post and published by Springer Science & Business Media. This book was released on 2013-11-21 with total page 1178 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
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 Turbulence and Transport Measurements in Alcator C Mod and Comparisons with Gyrokinetic Simulations written by Paul Chappell Ennever and published by . This book was released on 2016 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book An Assessment of the Department of Energy s Office of Fusion Energy Sciences Program written by National Research Council and published by National Academies Press. This book was released on 2001-05-07 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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%.
Download or read book Fusion Energy Update written by and published by . This book was released on 1978 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of Probes for Assessment of Ion Heat Transport and Sheath Heat Flux in the Boundary of the Alcator C Mod Tokamak written by Daniel Frederic Brunner and published by . This book was released on 2013 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress towards a viable fusion reactor will require comprehensive understanding of boundary plasma physics. Knowledge in this area has been growing, yet there are critical gaps. Measurements of the sheath heat flux transmission coefficient-a fundamental physical quantity whose theoretical value is ~ 7-have varied from 2 to 20. Values below 5 are physically impossible and have challenged the understanding of this very basic theory. In addition, measurements of ion temperature are sparse and ion energy transport is poorly understood. To this end a set of new diagnostics, including a surface thermocouple, ion sensitive probe, and retarding field analyzer, have been developed that can tolerate the extreme heat fluxes in the Alcator C-Mod boundary plasma. These probes are used to asses issues of heat flux and ion energy transport. Systematic studies with these new tools reveal the following: A comparison of surface thermocouples and Langmuir probes confirms standard sheath heat flux theory in a tokamak for the first time. The measurement of unphysically low sheath heat flux transmission coefficients and an anomalous increase in measured divertor pressure by Langmuir probes, which is also unphysical, are found the be linked. Plasma-neutral simulations indicate that these artifacts are due to the Langmuir probe bias modifying the local plasma. Important space charge limits to measurements with ion sensitive probes are found experimentally and explored in depth with a 1D kinetic simulation. These results clarify the plasma conditions under which an ion sensitive probe may be used to measure ion temperature and/or plasma potential. The retarding field analyzer is demonstrated to be a viable ion temperature diagnostic up to the last closed flux surface in C-Mod. A 1D fluid simulations is built to interpret edge ion heat transport. At high collisionality-where the fluid approximations are valid: the simulation reproduces the measured edge ion-to-electron temperature ratio (~ 2). However, at low collisionality-where fluid approximation is not valid-the simulation is not able to reproduce the experimental temperature ratio (~ 4). The addition of kinetic heat flux limiters can bring the simulated ratio into agreement with measurements. The value of heat flux limiter is found to be consistent with that expected from kinetic theory.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1994-08 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Documentation of Plasma Physics Pt 1 Experimental Plasma Physics and Theoretical Plasma Physics written by and published by . This book was released on 1981 with total page 558 pages. Available in PDF, EPUB and Kindle. Book excerpt:
