Download or read book H mode Pedestal Characteristics in ITER Shape Discharges on DIII D written by and published by . This book was released on 1998 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Characteristics of the H-mode pedestal are studied in Type 1 ELM discharges with ITER cross-sectional shape and aspect ratio. The scaling of the width of the edge step gradient region, [delta], which is most consistent with the data is with the normalized edge pressure, ([beta]{sub POL}{sup PED}){sup 0.4}. Fits of [delta] to a function of temperature, such as [rho]{sub POL}, are ruled out in divertor pumping experiments. The edge pressure gradient is found to scale as would be expected from infinite n ballooning mode theory; however, the value of the pressure gradient exceeds the calculated first stable limit by more than a factor of 2 in some discharges. This high edge pressure gradient is consistent with access to the second stable regime for ideal ballooning for surfaces near the edge. In lower q discharges, including discharges at the ITER value of q, edge second stability requires significant edge current density. Transport simulations give edge bootstrap current of sufficient magnitude to open second stable access in these discharges. Ideal kink analysis using current density profiles including edge bootstrap current indicate that before the ELM these discharges may be unstable to low n, edge localized modes.

Download or read book Scaling of ELM and H mode Pedestal Characteristics in ITER Shape Discharges in the DIII D Tokamak written by and published by . This book was released on 1997 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book H mode Pedestal Characteristics ELMs and Energy Confinement in ITER Shape Discharges on DIII D written by and published by . This book was released on 1997 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The H-mode confinement enhancement factor, H, is found to be strongly correlated with the height of the edge pressure pedestal in ITER shape discharges. In discharges with Type I ELMs the pedestal pressure is set by the maximum pressure gradient before the ELM and the width of the H-mode transport barrier. The pressure gradient before Type I ELMs is found to scale as would be expected for a stability limit set by ideal ballooning modes, but with values significantly in excess of that predicted by stability code calculations. The width of the H-mode transport barrier is found to scale equally well with pedestal P(POL)(2/3) or B(POL)1/2. The improved H value in high B(POL) discharges may be due to a larger edge pressure gradient and wider H-mode transport barrier consistent with their higher edge ballooning mode limit. Deuterium puffing is found to reduce H consistent with the smaller pedestal pressure which results from the reduced barrier width and critical pressure gradient. Type I ELM energy loss is found to be proportional to the change in the pedestal energy.

Download or read book The Effect of Plasma Shape on H Mode Pedestal Characteristics on DIII D written by and published by . This book was released on 1999 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The characteristics of the H-mode are studied in discharges with varying triangularity and squareness. The pressure at the top of the H-mode pedestal increases strongly with triangularity primarily due to an increase in the margin by which the edge pressure gradient exceeds the ideal ballooning mode first stability limit. Two models are considered for how the edge may exceed the ballooning mode limit. In one model [1], access to the ballooning mode second stable regime allows the edge pressure gradient and associated bootstrap current to continue to increase until an edge localized, low toroidal mode number, ideal kink mode is destabilized. In the second model [2], the finite width of the H-mode transport barrier, and diamagnetic effects raise the pressure gradient limit above the ballooning mode limit. We observe a weak inverse dependence of the width of the H-mode transport barrier, [Delta], on triangularity relative to the previously obtained [3] scaling [Delta] ∞ ([beta]{sub P}{sup PED})12. The energy loss for Type I ELMs increases with triangularity in proportion to the pedestal energy increase. The temperature profile is found to respond stiffly to changes in T{sup PED} at low temperature, while at high temperature the response is additive. The response of the density profile is also found to play a role in the response of the total stored energy to changes in the W{sup PED}.

Download or read book Nuclear Fusion written by and published by . This book was released on 2006 with total page 1144 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Active Control of Magneto hydrodynamic Instabilities in Hot Plasmas written by Valentin Igochine and published by Springer. This book was released on 2014-09-15 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity. However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for "old hands" and newcomers alike.

Download or read book Characteristics of the H mode Pedestal in Improved Confinement Scenarios in ASDEX Upgrade DIII D JET and JT 60U written by C. F. Maggi and published by . This book was released on 2006 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fusion Science and Technology written by and published by . This book was released on 2008 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Exploration of the Super H mode Regime on DIII D and Potential Advantages for Burning Plasma Devices written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a new high pedestal regime ("Super H-mode") we predicted and accessed DIII-D. Super H-mode was first achieved on DIII-D using a quiescent H-mode edge, enabling a smooth trajectory through pedestal parameter space. By exploiting Super H-mode, it has been possible to access high pedestal pressures at high normalized densities. And while elimination of Edge localized modes (ELMs) is beneficial for Super H-mode, it may not be a requirement, as recent experiments have maintained high pedestals with ELMs triggered by lithium granule injection. Simulations using TGLF for core transport and the EPED model for the pedestal find that ITER can benefit from the improved performance associated with Super H-mode, with increased values of fusion power and gain possible. In similar studies demonstrate that the Super H-mode pedestal can be advantageous for a steady-state power plant, by providing a path to increasing the bootstrap current while simultaneously reducing the demands on the core physics performance.

Download or read book Edge Pedestal Control in Quiescent H Mode Discharges in DIII D Using Co Plus Counter Neutral Beam Injection written by and published by . This book was released on 2008 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have made two significant discoveries in our recent studies of quiescent H-mode (QH-mode) plasmas in DIII-D. First, we have found that we can control the edge pedestal density and pressure by altering the edge particle transport through changes in the edge toroidal rotation. This allows us to adjust the edge operating point to be close to, but below the ELM stability boundary, maintaining the ELM-free state while allowing up to a factor of two increase in edge pressure. The ELM boundary is significantly higher in more strongly shaped plasmas, which broadens the operating space available for QH-mode and leads to improved core performance. Second, for the first time on any tokamak, we have created QH-mode plasmas with strong edge co-rotation; previous QH-modes in all tokamaks had edge counter rotation. This result demonstrates that counter NBI and edge counter rotation are not essential conditions for QH-mode. Both these investigations benefited from the edge stability predictions based on peeling-ballooning mode theory. The broadening of the ELM-stable region with plasma shaping is predicted by that theory. The theory has also been extended to provide a model for the edge harmonic oscillation (EHO) that regulates edge transport in the QH-mode. Many of the features of that theory agree with the experimental results reported either previously or in the present paper. One notable example is the prediction that co-rotating QH-mode is possible provided sufficient shear in the edge rotation can be created.

Download or read book Fusion Energy 1996 written by and published by . This book was released on 1997 with total page 1030 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the Sixteenth International Conference, formerly called the International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Montreal, 7-11 October 1996. The papers presented reflect the excellent progress achieved since the last conference in Seville 1994. Among many other achievements, the Tokamak Fusion Test Reactor has produced over 10 MW of fusion power, the JT-60U experiment has demonstrated plasma conditions equivalent to breakeven, the reversed shear mode has been demonstrated, low aspect ratio tokamaks have produced promising results and plans have been drawn up for powerful new inertial confinement fusion experiments.

Download or read book Characteristics of the H Mode Pedestal and Extrapolation to Iter written by and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: A271 CHARACTERISTICS OF THE H-MODE PEDESTAL AND EXTRAPOLATION TO ITER. The peeling-ballooning mode model for edge stability along with a model for the H-mode transport barrier width is used as an approach to estimating the H-mode pedestal conditions in ITER. Scalings of the barrier width based on ion-orbit loss, neutral penetration, and turbulence suppression are examined and empirical scalings of the barrier width are presented. An empirical scaling for the pedestal [beta] is derived based on ideas from stability and the empirical width scaling. The impact of the stability model and other factors on ELM size is discussed.

Download or read book Fusion Energy written by and published by . This book was released on 1997 with total page 1028 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Eighth Carolus Magnus Summer School on Plasma and Fusion Energy Physics written by and published by . This book was released on 2008 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comprehensive Dynamic Analysis of the H Mode Pedestal in DIII D written by Andrew Oakleigh Nelson and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The H-mode pedestal, characterized by steep gradients and reduced transport, is an essential feature of tokamak plasmas that couples the cold Scrape-Off-Layer (SOL) to the hot, fusion-relevant core. Though existing magnetohydrodynamic models yield some insight into the pedestal, they are (due to the complexity of interaction between the pedestal and the rest of the plasma) unable to fully predict pedestal behavior from generalized plasma conditions. To progress towards a more comprehensive understanding of pedestal dynamics, a larger context must be considered. Using state-of-the-art modeling and perturbative experimental techniques on DIII-D, this thesis develops a broader empirical understanding of dynamic pedestal behavior that will inform future modeling efforts.The pedestal obeys the physics of the continuity equation, which is set by the sourcing of particles, inter-ELM transport, and boundary conditions. In this light, three phenomena are selected for in-depth study: fueling, transport, and SOL interactions. First, the effect of particle sources on the pedestal structure is examined through a series of dedicated experiments on DIII-D. Gas and pellet fueling techniques are applied to change the neutral ionization profile at similar plasma conditions, showing that the structure of the pedestal can vary significantly with changes to the neutral source profile. Second, a novel experimental technique is used to probe the nature of inter-ELM turbulence, which is linked to the evolution and recovery of the pedestal structure. Additional current is induced in the pedestal region of several DIII-D plasmas, providing a first-of-its-kind experimental demonstration of microtearing modes (MTMs) in the tokamak edge. MTMs may contribute strongly to intense heat fluxes through the pedestal region, potentially providing the groundwork for an entirely physics-based predictive model of pedestal behavior. Finally, to develop a physics understanding of how the SOL boundary condition couples with the pedestal over the course of an entire plasma discharge, detailed modeling work is performed with the UEDGE code as a function of pedestal and ELM conditions. In this section, we establish a dynamic connection between the pedestal structure and divertor behavior, highlighting the need for a comprehensive approach to pedestal physics.

Download or read book Structure Stability and ELM Dynamics of the H mode Pedestal in DIII D written by M. E. Fenstermacher and published by . This book was released on 2005 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Plasma Physics Reports written by and published by . This book was released on 2004-07 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt: Publishes papers on plasma physics. The journal covers the following topics: high-temperature plasma physics, connected with the problem of controlled nuclear fusion based on magnetic and inertial confinement; physics of cosmic plasma including magnetosphere plasma, sun and stellar plasma, etc.; gas discharge plasma and plasma generated by laser and particle beams.