Download or read book Overview of Edge Localized Modes Control in Tokamak Plasmas written by Y. Liang and published by . This book was released on 2010* with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Edge Localized Mode Control by Resonant Magnetic Perturbations in Tokamak Plasmas written by Francois Orain and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growth of plasma instabilities called Edge Localized Modes (ELMs) in tokamaks results in the quasi-periodic relaxations of the edge plasma, potentially harmful for the divertor in ITER. One of the promising ELM control methods planned in ITER is the application of external resonant magnetic perturbations (RMPs), already efficient for ELM mitigation/suppression in current tokamak experiments. However a better understanding of the interaction between ELMs, RMPs and plasma flows is needed to make reliable predictions for ITER. In this perspective, non-linear modeling of ELMs and RMPs is done with the reduced MHD code JOREK, in realisitic geometry including the X-point and the Scrape-Off Layer. The two-fluid diamagnetic drifts, the neoclassical friction, a source of parallel rotation and RMPs have been implemented to simulate the RMP penetration consistently with the plasma response. As a first step, the plasma response to RMPs (without ELMs) is studied for JET, MAST and ITER realistic plasma parameters and geometry. Then the cyclic dynamics of the ELMs (without RMPs) is modeled for the first time in realistic geometry. After an ELM crash, the diamagnetic rotation is found to be instrumental to stabilize the plasma and to model the cyclic reconstruction and collapse of the plasma pressure profile. Last the ELM mitigation and suppression by RMPs is observed for the first time in modeling. The non-linear coupling of the RMPs with unstable modes is found to induce a continuous MHD activity in place of a large ELM crash, resulting in the mitigation of the ELMs. Over a threshold in magnetic perturbation, the full ELM suppression is also observed.
Download or read book Non linear Instabilities in the Edge of Tokamak Plasmas written by F. A. Calderon and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Type I Edge Localized Modes with N written by and published by . This book was released on 2008 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mitigating Edge localized Modes on the Mega Ampere Spherical Tokamak Using Resonant Magnetic Perturbations written by Peter Denner and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Type-I ELMy H-mode is planned to be the reference inductive operational scenario for ITER. However, unmitigated type-I ELMs would cause unacceptable damage to ITER's divertor, so a way of mitigating their effect must be found. This thesis focuses on the ergodization of the plasma edge using RMPs as a means of ELM control, and on related topics relevant to ergodic magnetic fields in MAST. Chapter 1 provides an introduction to nuclear fusion and chapter 2 provides an overview of ELMs. In chapter 3, the effect of ergodic fields on L-mode temperature profiles is calculated. It is found that no flattening of the temperature profile should be expected in MAST plasmas, which is in agreement with experimental results. In chapter 4, various metrics characterizing the degree of ergodicity in both L- and H-mode plasmas are calculated using vacuum modelling and compared with the amount of density pump-out observed experimentally in the those plasmas during the application of RMPs. The only parameter to show a correlation with the amount of density pump-out is the width of the laminar region. However, plasma response modelling provides a robust criterion for the occurrence of density pump-out that applies both to L- and H-mode plasmas. In chapter 5, the results of lower single-null H-mode ELM mitigation experiments using n=4 and n=6 RMPs are presented. ELM mitigation is achieved and refuelling of plasmas that had begun to undergo pump-out is successfully demonstrated. Both ELM frequency and density pump-out are found to increase with ELM coil current above a certain threshold. An analysis of an ergodic magnetic field formed by a current sheet on a rational surface is presented in chapter 6. Various properties of this ergodic field are calculated and compared with experimental effects observed in the plasma. Some agreement is found between the experimental data and the modelling. Finally, a summary of the thesis is given in chapter 7.
Download or read book Magnetohydrodynamic Stability of Tokamaks written by Hartmut Zohm and published by John Wiley & Sons. This book was released on 2015-02-09 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book bridges the gap between general plasma physics lectures and the real world problems in MHD stability. In order to support the understanding of concepts and their implication, it refers to real world problems such as toroidal mode coupling or nonlinear evolution in a conceptual and phenomenological approach. Detailed mathematical treatment will involve classical linear stability analysis and an outline of more recent concepts such as the ballooning formalism. The book is based on lectures that the author has given to Master and PhD students in Fusion Plasma Physics. Due its strong link to experimental results in MHD instabilities, the book is also of use to senior researchers in the field, i.e. experimental physicists and engineers in fusion reactor science. The volume is organized in three parts. It starts with an introduction to the MHD equations, a section on toroidal equilibrium (tokamak and stellarator), and on linear stability analysis. Starting from there, the ideal MHD stability of the tokamak configuration will be treated in the second part which is subdivided into current driven and pressure driven MHD. This includes many examples with reference to experimental results for important MHD instabilities such as kinks and their transformation to RWMs, infernal modes, peeling modes, ballooning modes and their relation to ELMs. Finally the coverage is completed by a chapter on resistive stability explaining reconnection and island formation. Again, examples from recent tokamak MHD such as sawteeth, CTMs, NTMs and their relation to disruptions are extensively discussed.
Download or read book Nonlinear Dynamics written by Todd Evans and published by IntechOpen. This book was released on 2010-01-01 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume covers a diverse collection of topics dealing with some of the fundamental concepts and applications embodied in the study of nonlinear dynamics. Each of the 15 chapters contained in this compendium generally fit into one of five topical areas: physics applications, nonlinear oscillators, electrical and mechanical systems, biological and behavioral applications or random processes. The authors of these chapters have contributed a stimulating cross section of new results, which provide a fertile spectrum of ideas that will inspire both seasoned researches and students.
Download or read book Edge localized modes in Tokamaks written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heat flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. As a result, encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.
Download or read book Nonlinear Dynamics written by Todd Evans and published by IntechOpen. This book was released on 2010-01-01 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume covers a diverse collection of topics dealing with some of the fundamental concepts and applications embodied in the study of nonlinear dynamics. Each of the 15 chapters contained in this compendium generally fit into one of five topical areas: physics applications, nonlinear oscillators, electrical and mechanical systems, biological and behavioral applications or random processes. The authors of these chapters have contributed a stimulating cross section of new results, which provide a fertile spectrum of ideas that will inspire both seasoned researches and students.
Download or read book Magnetic Control of Tokamak Plasmas written by Marco Ariola and published by Springer. This book was released on 2016-02-23 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a complete treatment of work done to resolve the problems of position-, current-, and shape-control of plasma in tokamak-type (toroidal) devices being studied as a potential means of commercial energy production by nuclear fusion. Modelling and control are both detailed, allowing non-expert readers to understand the control problem. Starting from the magneto-hydro-dynamic equations, all the steps needed for the derivation of plasma state-space models are enumerated with frequent recall of the basic concepts of electromagnetics. The control problem is then described, beginning with the control of current and position—vertical and radial—control and progressing to the more challenging shape control. The solutions proposed vary from simple PIDs to more sophisticated MIMO controllers. The second edition of Magnetic Control of Tokamak Plasmas contains numerous updates and a substantial amount of completely new material covering areas such as: • modelling and control of resistive wall modes—the most important non-axisimmetric mode; • the isoflux approach for shape control; • a general approach for the control of limiter plasmas; • the use of inner vessel coils for vertical stabilization; and • significantly enhanced treatment of plasma-shape control at JET, including experimental results and introducing a method implemented for operation in the presence of current saturations. Whenever possible, coverage of the various topics is rounded out with experimental results obtained on currently existing tokamaks. The book also includes a presentation of the typical actuators and sensors used for control purposes in tokamaks. Some mathematical details are given in the appendices for the interested reader. The ideas formulated in this monograph will be of great practical help to control engineers, academic researchers and graduate students working directly with problems related to the control of nuclear fusion. They will also stimulate control researchers interested more generally in the advanced applications of the discipline. Advances in Industrial Control aims to report and encourage the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control.
Download or read book Edge Localized Mode Dynamics and Transport in the Scrape Off Layer of the DIII D Tokamak written by and published by . This book was released on 2004 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are produced in the low field side, are poloidally localized and are composed of fast bursts (≈20 to 40 [mu]s long) of hot, dense plasma on a background of less dense, colder plasma (≈5 x 1018 m{sup {+-}3}, 50 eV) possibly created by the bursts themselves. The ELMs travel radially in the scrapeoff layer (SOL), starting at the separatrix at ≈450 m/s, and slow down to ≈150 m/s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length (≈1.2 to 1.5 cm) is much shorter than the density decay length (≈3 to 8 cm), and the latter decreases with increasing pedestal (and SOL) density. The local particle and energy flux at the midplane wall during the bursts are 10% to 50% (≈1 to 2 x 1021 m{sup {+-}2} s{sup {+-}1}) and 1% to 2 % (≈20 to 30 kW/m2) respectively of the LCFS average fluxes, indicating that particles are transported radially much more efficiently than heat. Evidence is presented suggesting toroidal rotation of the ELM plasma in the SOL. The ELM plasma density and temperature increase linearly with discharge/pedestal density up to a Greenwald fraction of ≈0.6, and then decrease resulting in more benign (grassier) ELMs.
Download or read book Frontiers in Fusion Research II written by Mitsuru Kikuchi and published by Springer. This book was released on 2015-09-03 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews recent progress in our understanding of tokamak physics related to steady state operation, and addresses the scientific feasibility of a steady state tokamak fusion power system. It covers the physical principles behind continuous tokamak operation and details the challenges remaining and new lines of research towards the realization of such a system. Following a short introduction to tokamak physics and the fundamentals of steady state operation, later chapters cover parallel and perpendicular transport in tokamaks, MHD instabilities in advanced tokamak regimes, control issues, and SOL and divertor plasmas. A final chapter reviews key enabling technologies for steady state reactors, including negative ion source and NBI systems, Gyrotron and ECRF systems, superconductor and magnet systems, and structural materials for reactors. The tokamak has demonstrated an excellent plasma confinement capability with its symmetry, but has an intrinsic drawback with its pulsed operation with inductive operation. Efforts have been made over the last 20 years to realize steady state operation, most promisingly utilizing bootstrap current. Frontiers in Fusion Research II: Introduction to Modern Tokamak Physics will be of interest to graduate students and researchers involved in all aspects of tokamak science and technology.
Download or read book Radiative Instabilities in the Tokamak Scrape off Layer During Edge localized Mode Activity written by Per O. F. Helander and published by . This book was released on 1995 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pattern Recognition in Spaces of Probability Distributions for the Analysis of Edge localized Modes in Tokamak Plasmas written by Aqsa Shabbir and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics of the L H Transition VH mode Evolution Edge Localized Modes and R F Driven Confinement Control in Tokamaks written by and published by . This book was released on 1995 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several novel theoretical results related to L --> H transition physics, VH-mode evolution, Edge Localized Modes and active confinement control are presented. Critical issues are identified, results are discussed and important unresolved questions are listed. The basic physics is discussed in the contexts of current experiments and of ITER.
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 Material Migration in Tokamak Plasmas with a Three dimensional Boundary written by Ruth Laengner and published by Forschungszentrum Jülich. This book was released on 2013 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt:
