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 and published by . This book was released on 2005 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Empirical Study of Ne in H Mode Pedestal in DIII D written by D. M. Thomas and published by . This book was released on 2004 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book OVERVIEW OF H MODE PEDESTAL RESEARCH ON DIII D written by and published by . This book was released on 2001 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing an understanding of the processes that control the H-mode transport barrier is motivated by the significant impact this small region (typically

Download or read book Well a day My Poor Heart written by and published by . This book was released on 1795* with total page 1 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 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 Enhanced H mode Pedestals with Lithium Injection in DIII D written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Periods of edge localized mode (ELM)-free H-mode with increased pedestal pressure and width were observed in the DIII-D tokamak when density fluctuations localized to the region near the separatrix were present. Injection of a powder of 45 [mu]m diameter lithium particles increased the duration of the enhanced pedestal phases to up to 350 ms, and also increased the likelihood of a transition to the enhanced phase. Lithium injection at a level sufficient for triggering the extended enhanced phases resulted in significant lithium in the plasma core, but carbon and other higher Z impurities as well as radiated power levels were reduced. Recycling of the working deuterium gas appeared unaffected by this level of lithium injection. The ion scale, k[theta] [rho]s ~ 0.1-0.2, density fluctuations propagated in the electron drift direction with f ~ 80 kHz and occurred in bursts every ~1 ms. The fluctuation bursts correlated with plasma loss resulting in a flattening of the pressure profile in a region near the separatrix. This localized flattening 2 allowed higher overall pedestal pressure at the peeling-ballooning stability limit and higher pressure than expected under the EPED model due to reduction of the pressure gradient below the "ballooning critical profile". Furthermore, reduction of the ion pressure by lithium dilution may contribute to the long ELM-free periods.

Download or read book Nuclear Fusion written by and published by . This book was released on 2006-12 with total page 632 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 808 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Power Exhaust in Fusion Plasmas written by Wojciech Fundamenski and published by Cambridge University Press. This book was released on 2010 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete and up-to-date summary of power exhaust in fusion plasmas, for academic researchers and graduate students in plasma physics.

Download or read book Plasma Surface Interactions in Controlled Fusion Devices written by and published by . This book was released on 1978 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computational Methods in Plasma Physics written by Stephen Jardin and published by CRC Press. This book was released on 2010-06-02 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Assuming no prior knowledge of plasma physics or numerical methods, Computational Methods in Plasma Physics covers the computational mathematics and techniques needed to simulate magnetically confined plasmas in modern magnetic fusion experiments and future magnetic fusion reactors. Largely self-contained, the text presents the basic concepts neces

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:

Download or read book Weak Turbulence in a Homogeneous Plasma written by Ronald C. Davidson and published by . This book was released on 1966 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theory of Fusion Plasmas written by Olivier Sauter and published by American Institute of Physics. This book was released on 2008-12-02 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Joint Varenna-Lausanne International Workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favorable for informal and in depth discussions. Invited and contributed papers present state-of-the art researches in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always allows a fruitful mix of experienced researchers and students, to allow for a better understanding of the key theoretical physics models and applications, such as: Theoretical issues related to burning plasmas; Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive; Macroinstabilities; Plasma-Edge Physics and Divertors; Fast particles instabilities.