On the Interactions of Magnetic Fluctuations, Zonal Flows, & Microturbulence in Fusion Plasmas PDF Download
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Author: Zachary R. Williams
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A key aspect of turbulent dynamics is the inherent coupling of fluctuations at disparate spatial scales. One significant multi-scale phenomenon is the degradation of zonal flows by large-scale radial magnetic perturbations that result in an increase of small-scale microturbulence and affiliated transport. Two prominent sources of radial magnetic field fluctuations are examined in this thesis, resonant magnetic perturbations (RMPs) in tokamaks and tearing modes in reversed-field pinches (RFPs). This interplay is studied with gyrokinetics to model DIII-D tokamak and MST RFP plasmas. An imposed magnetic perturbation that mimics a tearing mode increases the level of trapped-electron-mode turbulence to a level consistent with fluctuation and transport measurements in MST plasmas. This motivated a dedicated experiment on DIII-D to study the impact of varying RMP amplitude on turbulence in inboard-limited L-mode plasmas. Highlights of the theory-experiment comparison are presented. To study the self-consistent multi-scale interaction of the tearing mode physics, nonlinear simulations containing both tearing mode (driven from equilibrium current gradients) and microinstability scales are performed in a slab geometry. The system is characterized by distinct microinstability- and tearing-dominated regimes. Within the microturbulence-dominated phase, the slow tearing mode growth corresponds directly to a decay in zonal flow. The turbulence levels driven at both large and small scales is increased from single-scale simulations, clearly demonstrated the importance of cross scale interactions.
Author: Zachary R. Williams
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A key aspect of turbulent dynamics is the inherent coupling of fluctuations at disparate spatial scales. One significant multi-scale phenomenon is the degradation of zonal flows by large-scale radial magnetic perturbations that result in an increase of small-scale microturbulence and affiliated transport. Two prominent sources of radial magnetic field fluctuations are examined in this thesis, resonant magnetic perturbations (RMPs) in tokamaks and tearing modes in reversed-field pinches (RFPs). This interplay is studied with gyrokinetics to model DIII-D tokamak and MST RFP plasmas. An imposed magnetic perturbation that mimics a tearing mode increases the level of trapped-electron-mode turbulence to a level consistent with fluctuation and transport measurements in MST plasmas. This motivated a dedicated experiment on DIII-D to study the impact of varying RMP amplitude on turbulence in inboard-limited L-mode plasmas. Highlights of the theory-experiment comparison are presented. To study the self-consistent multi-scale interaction of the tearing mode physics, nonlinear simulations containing both tearing mode (driven from equilibrium current gradients) and microinstability scales are performed in a slab geometry. The system is characterized by distinct microinstability- and tearing-dominated regimes. Within the microturbulence-dominated phase, the slow tearing mode growth corresponds directly to a decay in zonal flow. The turbulence levels driven at both large and small scales is increased from single-scale simulations, clearly demonstrated the importance of cross scale interactions.
Author: Taweesak Jitsuk
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Global tearing modes (TMs) can interact among themselves or with small-scale instabilities, exerting profound influence on fusion plasma performance. Experiments in reversed-field pinches (RFPs) demonstrate that TMs couple, cascade, and cause robust transport, while partial suppression of their activity can result in enhanced confinement. The presence of unstable drift waves during the TM cascade in the RFP allows interactions with microinstabilities. Local gyrokinetic simulations with externally imposed magnetic perturbations modeling TMs have demonstrated that the magnetic perturbations erode zonal flows that are nonlinearly generated by the microinstabilities, resulting in higher turbulence levels. Similarly, when resonant magnetic perturbations (RMPs) are applied to mitigate edge-localized modes in tokamaks, the RMPs suppress the zonal flows, which in turn can increase the heat flux. These phenomena highlight the importance of multi-scale interactions between large-scale magnetic fluctuations and zonal-flow-regulated microturbulence, an incompletely understood topic. For a comprehensive understanding of these interactions, self-consistent computations simultaneously evolving TMs and small-scale fluctuations are needed. Here, calculations are performed with the global gyrokinetic code GENE, which was modified to include a background current density. This provides the TM drive, and it is verified that the modified GENE code properly models global TMs. Working towards multi-scale simulations, a non-reversed RFP discharge is studied; linear simulations show that the non-reversed equilibrium is unstable to large-scale TMs, which dominate in the core region, while small-scale density-gradient-driven TEMs dominate near the plasma edge. Nonlinear simulations with only TMs show that large-scale TMs in the core are coupled and excite smaller-scale stable TMs. The latter resonates at rational surfaces closer to the edge, where TEMs are active, indicating that multi-scale interactions are possible. In nonlinear global TEM simulations, zonal flows dominate the saturated state, leading to negligible transport in the absence of TMs, consistent with local simulations. When TMs and TEMs are simultaneously included in nonlinear simulations, TMs partially erode zonal flows. This erosion of zonal flows disrupts energy mediation by zonal flows, leading to a significant increase in heat flux. However, the zonal flows remain a dominant characteristic of fluctuations, causing the transport fluxes to remain much smaller than in experiments. To quantitatively reproduce experiments in future work, higher density gradients are required to weaken the zonal flows, or a stronger TM drive is needed to intensify the magnetic perturbations. These multi-scale simulations offer valuable insights for understanding RFP experiments and studying potential interactions of MHD phenomena and microturbulence in tokamaks. In contrast to TEM behavior, static magnetic perturbations do not strongly affect the ITG-driven turbulence of RFPs. This is because the ITG in RFPs is characterized by a slab limit and does not rely as strongly on zonal flows for saturation; instead, it depends on marginal modes. Zonal flows, on the other hand, play a crucial role in toroidal-ITG saturation. This prompts the exploration of saturation-channel selection rules that capture the preference of the toroidal limit for zonal flows and of the slab limit for marginal modes. Nonlinear coupling quantities are determined, and the triplet correlation time and mode overlap results are presented. Combining these metrics allows for predicting the dominant saturation channel for a given physical-parameter scenario, providing a powerful new tool that will aid a deeper understanding of nonlinear interactions and may also be used to enhance reduced models of anomalous transport.
Author: Wendell Horton
Publisher: World Scientific
ISBN: 9814383546
Category : Science
Languages : en
Pages : 518
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Book Description
The book explains how magnetized plasmas self-organize in states of electromagnetic turbulence that transports particles and energy out of the core plasma faster than anticipated by the fusion scientists designing magnetic confinement systems in the 20th century. It describes theory, experiments and simulations in a unified and up-to-date presentation of the issues of achieving nuclear fusion power.
Author: Olivier Sauter
Publisher: American Institute of Physics
ISBN: 9780735406001
Category : Science
Languages : en
Pages : 400
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Book Description
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.
![Interaction of Magnetic Plasma Fluctuations with Fusion-produced [alpha]-particles PDF](https://books.google.com/books/content/images/frontcover/i13NtgAACAAJ?fife=w80-h100)
Author: B. Coppi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Boris Galperin
Publisher: Cambridge University Press
ISBN: 1107043883
Category : Nature
Languages : en
Pages : 527
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Book Description
Presents a comprehensive, multidisciplinary volume on the physics of zonal jets, from the leading experts, for graduate students and researchers.
Author: P.C Stangeby
Publisher: CRC Press
ISBN: 9780750305594
Category : Science
Languages : en
Pages : 738
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Book Description
The Plasma Boundary of Magnetic Fusion Devices introduces the physics of the plasma boundary region, including plasma-surface interactions, with an emphasis on those occurring in magnetically confined fusion plasmas. The book covers plasma-surface interaction, Debye sheaths, sputtering, scrape-off layers, plasma impurities, recycling and control, 1D and 2D fluid and kinetic modeling of particle transport, plasma properties at the edge, diverter and limiter physics, and control of the plasma boundary. Divided into three parts, the book begins with Part 1, an introduction to the plasma boundary. The derivations are heuristic and worked problems help crystallize physical intuition, which is emphasized throughout. Part 2 provides an introduction to methods of modeling the plasma edge region and for interpreting computer code results. Part 3 presents a collection of essays on currently active research hot topics. With an extensive bibliography and index, this book is an invaluable first port-of-call for researchers interested in plasma-surface interactions.
Author: National Academies of Sciences Engineering and Medicine
Publisher:
ISBN: 9780309677608
Category :
Languages : en
Pages : 291
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Book Description
Plasma Science and Engineering transforms fundamental scientific research into powerful societal applications, from materials processing and healthcare to forecasting space weather. Plasma Science: Enabling Technology, Sustainability, Security and Exploration discusses the importance of plasma research, identifies important grand challenges for the next decade, and makes recommendations on funding and workforce. This publication will help federal agencies, policymakers, and academic leadership understand the importance of plasma research and make informed decisions about plasma science funding, workforce, and research directions.
Author: Sergei Krasheninnikov
Publisher: Springer
ISBN: 9783030495961
Category : Science
Languages : en
Pages : 0
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Book Description
This book reviews the current state of understanding concerning edge plasma, which bridges hot fusion plasma, with a temperature of roughly one million degrees Kelvin with plasma-facing materials, which have melting points of only a few thousand degrees Kelvin. In a fact, edge plasma is one of the keys to solution for harnessing fusion energy in magnetic fusion devices. The physics governing the processes at work in the edge plasma involves classical and anomalous transport of multispecies plasma, neutral gas dynamics, atomic physics effects, radiation transport, plasma-material interactions, and even the transport of plasma species within the plasma-facing materials. The book starts with simple physical models, then moves on to rigorous theoretical considerations and state-of-the-art simulation tools that are capable of capturing the most important features of the edge plasma phenomena. The authors compare the conclusions arising from the theoretical and computational analysis with the available experimental data. They also discuss the remaining gaps in their models and make projections for phenomena related to edge plasma in magnetic fusion reactors.
Author: D. Biskamp
Publisher: Cambridge University Press
ISBN: 0521582881
Category : Medical
Languages : en
Pages : 403
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Book Description
This book, first published in 2000, is a comprehensive introduction to this major topic in plasma physics; for graduates and researchers.
