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 Implications from Dimensionless Parameter Scaling Experiments written by and published by . This book was released on 1996 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dimensionless parameter scaling approach is increasingly useful for predicting future tokamak performance and guiding theoretical models of energy transport. Experiments to determine the [rho]* (gyroradius normalized to plasma size) scaling have been carried out in many regimes. The electron [rho]* scaling is always ''gyro-Bohm'', while the ion [rho]* scaling varied with regime. The ion variation is correlated with both density scale length (L mode, H mode) and current profile. The ion [rho]* scaling in the low-q, H-mode regime is gyro-Bohm, which is the most favorable confinement scaling observed. New experiments in [beta] scaling and collisionality scaling have been carried out in low-q discharges in both L mode and H mode. In L mode, global analysis shows that there is a slightly unfavorable [beta] dependence ([beta]{sup -0.1}) and no [nu]* dependence. In H-mode, global analysis finds a weak [beta] dependence ([beta]{sup 0.1}) and an unfavorable dependence on [nu]*. The lack of significant [beta] scaling spans the range of [beta]{sub N} from 0.25 to 2.0. The very small [beta] dependence in L mode and H mode is in contradiction with the standard global scaling relations. This contradiction in H mode may be indicative of the impact on the H-mode database of low-n tearing instabilities which are observed at slightly higher [beta]{sub N} in the [beta] scaling experiments. The measured [beta] and [nu]* scalings explain the weak density dependence observed in engineering parameter scans. It also points to the power of the dimensionless parameter approach, since it is possible to obtain a definitive size scaling from experiments on a single tokamak.
Download or read book Understanding Transport Through Dimensionless Parameter Scaling Experiments written by and published by . This book was released on 1997 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The related methods of dimensional analysis, similarity, and scale invariance provide a powerful technique for analyzing physical systems. For example, the complex plasma dynamics governed by the Vlasov-Maxwell system of equations can be characterized by sets of dimensionless quantities through the application of these techniques. Significant progress has been made recently towards predicting and understanding radial heat transport using dimensionless parameter scaling techniques. Previous experiments on the DIII-D tokamak have measured the variation of heat transport with the relative gyroradius ([rho]*); in this paper, the scaling of heat transport with plasma beta ([beta]) and normalized collisionality ([nu]) for L-mode and H-mode plasmas on the DIII-D tokamak is reported. Following the scale invariance approach to confinement scaling, the thermal diffusivity ([chi]) is assumed to depend only on local dimensionless quantities. Understanding the beta and collisionality scaling of transport helps to differentiate between various proposed mechanisms of turbulent transport and allows the origin of power degradation and density scaling of confinement to be determined.
Download or read book 16th IEEE NPSS Symposium Fusion Engineering written by and published by . This book was released on 1995 with total page 900 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tokamaks written by John Wesson and published by Oxford University Press. This book was released on 2011-10-13 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1996 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Department of Energy s Restructured Fusion Energy Sciences Program written by United States. Congress. House. Committee on Science. Subcommittee on Energy and Environment and published by . This book was released on 1996 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book EXPERIMENTAL VALIDATION OF SIMILARITY IN HIGH TEMPERATURE PLASMAS written by and published by . This book was released on 2001 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scaling of energy transport with dimensionless parameters has been measured in high temperature plasmas with the goals of guiding theory and predicting energy confinement in future fusion devices. Validation of this approach requires demonstration of similarity in plasmas with identical dimensionless parameters but very different physical parameters. Within measurement uncertainties, the heat diffusivities and global energy confinement exhibit similarity in high confinement regimes on the DIII-D and JET tokamaks and in low confinement regimes on the DIII-D and AlcatorC-Mod tokamaks.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Testing the P Scaling of Thermal Transport Modes written by D. R. Mikkelsen and published by . This book was released on 1997 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Self Organization of Hot Plasmas written by Yu.N. Dnestrovskij and published by Springer. This book was released on 2014-07-08 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this monograph the author presents the Canonical Profile Transport Model or CPTM as a rather general mathematical framework to simulate plasma discharges. The description of hot plasmas in a magnetic fusion device is a very challenging task and many plasma properties still lack a physical explanation. One important property is plasma self-organization. It is very well known from experiments that the radial profile of the plasma pressure and temperature remains rather unaffected by changes of the deposited power or plasma density. The attractiveness of the CPTM is that it includes the effect of self-organization in the mathematical model without having to recur to particular physical mechanisms. The CPTM model contains one dimensional transport equations for ion and electron temperatures, plasma density and toroidal rotation velocity. These equations are well established and in fact are essentially a reformulation the laws of energy, particle and momentum conservation. But the expressions for the energy and particle fluxes, including certain critical gradients, are new. These critical gradients can be determined using the concept of canonical profiles for the first time formulated in great detail in the book. This concept represents a totally new approach to the description of transport in plasmas. Mathematically, the canonical profiles are formulated as a variational problem. To describe the temporal evolution of the plasma profiles, the Euler equation defining the canonical profiles is solved together with the transport equations at each time step. The author shows that in this way it is possible to describe very different operational scenarios in tokamaks (L-Mode, H-Mode, Advanced Modes, Radiating Improved Modes etc...), using one unique principle. The author illustrates the application of this principle to the simulation of plasmas on leading tokamak devices in the world (JET, MAST, T-10, DIII-D, ASDEX-U, JT-60U). In all cases the small differences between the calculated profiles for the ion and electron temperatures and the experimental is rather confirm the validity of the CPTM. In addition, the model also describes the temperature and density pedestals in the H-mode and non steady-state regimes with current and density ramp up. The proposed model therefore provides a very useful mathematical tool for the analysis of experimental results and for the prediction of plasma parameters in future experiments.
Download or read book Plasma Science written by National Research Council and published by National Academies Press. This book was released on 1995-01-01 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma science is the study of ionized states of matter. This book discusses the field's potential contributions to society and recommends actions that would optimize those contributions. It includes an assessment of the field's scientific and technological status as well as a discussion of broad themes such as fundamental plasma experiments, theoretical and computational plasma research, and plasma science education.
Download or read book BETA SCALING OF TRANSPORT ON THE DIII D TOKAMAK IS TRANSPORTELECTROSTATIC OR ELECTROMAGNETIC written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Determining the scaling of transport with ([beta]), the ratio of the plasma kinetic pressure to the magnetic pressure, helps to differentiate between various proposed theories of turbulent transport since mechanisms that are primarily electrostatic show little change in transport with increasing [beta], while primarily electromagnetic mechanisms generally have a strong unfavorable [beta] scaling. Experiments on the DIII-D tokamak have measured the [beta] scaling of heat transport with all of the other dimensionless parameters held constant in high confinement mode (H-mode) plasmas with edge localized modes (ELMs). A four point scan varied [beta] from 30% to 85% of the ideal ballooning stability limit (normalized beta from 1.0 to 2.8) and found no change in the normalized confinement time, i.e., B[tau][sub th] [infinity] [beta][sup -0.01] [+-] 0.09. The measured thermal diffusivities, normalized to the Bohm diffusion coefficient, also did not vary during the [beta] can to within the experimental uncertainties, whereas the normalized helium particle transport decreased with increasing [beta]. The H-mode pedestal [beta] varied in concert with the core [beta] and showed no signs of saturation. This weak, possibly non-existent, [beta] scaling of transport favors primarily electrostatic mechanisms such as E x B transport, and is in marked disagreement with the strong unfavorable [beta] dependence contained in empirical scaling relations derived from multi-machine H-mode confinement databases.
Download or read book Fusion Energy written by and published by . This book was released on 1997 with total page 962 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dimensionless Parameters Scaling Laws and the Implications for ETG written by and published by . This book was released on 1995 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: ETG will be useful in resolving several physical issues relevant to Spherical Tokamak Reactor concepts. First, it will provide a test of whether transport is Bohm or gyro-Bohm in nature. The second point is that ETG will operate in a completely different range of [rho]* space from other high performance machines, opening up a previously inaccessible region of parameter space. ETG is also a (very) high-[beta] machine. It would be the only device that would have all of its parameters except [rho]* similar to those of a Spherical tokamak Reactor. If it turns out that the transport scales definitively as either Bohm or gyro-Bohm, then extrapolation to reactor conditions with significantly lower values of [rho]* would become more credible. It is also shown that in general one cannot obtain a power law relation in the dimensionless variables for the confinement tim from a power law fit to the engineering variables. It is shown, however, that if T{sub i}/T{sub e} and n{sub i}/n{sub e} are constant or if a modified definition of certain dimensionless variables is adopted, then such a power law conversion is possible.
Download or read book Nuclear Fusion written by C.M. Braams and published by CRC Press. This book was released on 2002-06-20 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fusion research started over half a century ago. Although the task remains unfinished, the end of the road could be in sight if society makes the right decisions. Nuclear Fusion: Half a Century of Magnetic Confinement Fusion Research is a careful, scholarly account of the course of fusion energy research over the past fifty years. The authors outline the different paths followed by fusion research from initial ignorance to present understanding. They explore why a particular scheme would not work and why it was more profitable to concentrate on the mainstream tokamak development. The book features descriptive sections, in-depth explanations of certain physical and technical issues, scientific terms, and an extensive glossary that explains relevant abbreviations and acronyms.
Download or read book Fusion Energy Program written by United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Investigations and Oversight and published by . This book was released on 1990 with total page 820 pages. Available in PDF, EPUB and Kindle. Book excerpt:
