Improved Macroscopic Plasma Modeling and Its Application to Tokamak Disruptions PDF Download
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Author: Brian Cornille
Publisher:
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Languages : en
Pages : 0
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Book Description
This dissertation presents results from two topics in tokamak disruption modeling. The first usessimulation to elucidate the observations from MST tokamak disharge experiments on suppression of runaway electrons (RE) with resonant magnetic perturbations (RMP). When applying RMPs having a single poloidal harmonic, an m = 1 RMP does not suppress RE while and m = 3 RMP achieves full suppression [Munaretto et al., Nuclear Fusion 60, 046024 (2020)]. Magnetohydrody- namics (MHD) simulation of the experiment indicates that the m = 3 RMP produces a substantial region of chaotic magnetic fields whereas the m = 1 RMP produces negligible changes in field topology compared to no RMP. Using snapshots of the MHD simulation fields, full-orbit relativis- tic electron test particle computations show [approximately equal to] 50% loss from the m = 3 RMP compared to the 10 -15% loss from the m = 1 RMP. Test particle computations of the m = 3 RMP case in the time-evolving MHD simulation fields show correlation between MHD activity and enhanced particle losses, but finds similar total electron confinement and field snapshots. The second topic presents a novel enhancement to vertical displacement computations in NIMROD [Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. We present development of a quasi-static meshed vacuum region approach for treatment of computations with a resistive wall representation. With this approach a magnetostatic problem is solved for an external vacuum region while coupled through a thin-wall approximation to the implicit time advance of the plasma. Verification of the implementation is presented along with demonstration of its increased robustness in challenging geometries compared to the incumbent implementation.
Author: Brian Cornille
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
This dissertation presents results from two topics in tokamak disruption modeling. The first usessimulation to elucidate the observations from MST tokamak disharge experiments on suppression of runaway electrons (RE) with resonant magnetic perturbations (RMP). When applying RMPs having a single poloidal harmonic, an m = 1 RMP does not suppress RE while and m = 3 RMP achieves full suppression [Munaretto et al., Nuclear Fusion 60, 046024 (2020)]. Magnetohydrody- namics (MHD) simulation of the experiment indicates that the m = 3 RMP produces a substantial region of chaotic magnetic fields whereas the m = 1 RMP produces negligible changes in field topology compared to no RMP. Using snapshots of the MHD simulation fields, full-orbit relativis- tic electron test particle computations show [approximately equal to] 50% loss from the m = 3 RMP compared to the 10 -15% loss from the m = 1 RMP. Test particle computations of the m = 3 RMP case in the time-evolving MHD simulation fields show correlation between MHD activity and enhanced particle losses, but finds similar total electron confinement and field snapshots. The second topic presents a novel enhancement to vertical displacement computations in NIMROD [Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. We present development of a quasi-static meshed vacuum region approach for treatment of computations with a resistive wall representation. With this approach a magnetostatic problem is solved for an external vacuum region while coupled through a thin-wall approximation to the implicit time advance of the plasma. Verification of the implementation is presented along with demonstration of its increased robustness in challenging geometries compared to the incumbent implementation.
Author: Hartmut Zohm
Publisher: John Wiley & Sons
ISBN: 3527412328
Category : Science
Languages : en
Pages : 254
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Book Description
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.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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The behavior of the scrape-off layer (SOL) region in tokamaks is believed to play an important role determining the overall device performance. In addition, control of the exhaust power has become one of the most important issues in the design of future devices such as ITER and TPX. This paper presents the results of application of 2-D fluid models to the DII-D tokamak, and research into the importance of processes which are inadequately treated in the fluid models. Comparison of measured and simulated profiles of SOL plasma parameters suggest the physics model contained in the UEDGE code is sufficient to simulate plasmas which are attached to the divertor plates. Experimental evidence suggests the presence of enhanced plasma recombination and momentum removal leading to the existence of detached plasma states. UEDGE simulation of these plasmas obtains a bifurcation to a low temperature plasma at the divertor, but the plasma remains attached. Understanding the physics of this detachment is important for the design of future devices. Analytic studies of the behavior of SOL plasmas enhance our understanding beyond that achieved with fluid modeling. Analysis of the effect of drifts on sheath structure suggest these drifts may play a role in the detachment process. Analysis of the turbulent-transport equations indicate a bifurcation which is qualitatively similar to the experimentally different behavior of the L- and H-mode SOL. Electrostatic simulations of conducting wall modes suggest possible control of the SOL width by biasing.
Author: Alexandre Fil
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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Book Description
Plasma disruptions are events occuring in tokamaks which result in the total loss of the plasma confinement and the end of the discharge. These disruptions are rapid and violent events and they can damage the tokamak walls and its structure if they are not controlled. A Disruption Mitigation System (DMS) is thus mandatory in ITER in order to reduce electromagnetic forces, mitigate heat loads and avoid Runaway Electrons (RE) generated by plasma disruptions. These combined objectives make the design of the DMS a complex and challenging task, for which substantial input from both experiments and modeling is needed. We present here modeling results on disruption mitigation by Massive Gas Injection (MGI), which is one of the main methods considered for the DMS of ITER. First, a model which stems from first principles is given for the tranport of neutrals in a plasma and applied to the study of the interaction of the MGI with the plasma. Main mechanisms responsible for the penetration of the neutral gas are described and studied. Charge-exchange processes between the neutrals and the ions of the plasma is found to play a major role. Then, the 3D non linear MHD code JOREK is applied to the study of MGI-triggered disruptions with a particular focus on the thermal quench phase and the MHD events which are responsible for it. The simulation results are compared to experiments done on the JET tokamak.
Author: Y.N. Dnestrovskii
Publisher: Springer
ISBN: 9783642825941
Category : Science
Languages : en
Pages : 0
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Book Description
This book is devoted to mathematical modeling of tokamak plasma. Since the appearance in 1982 of the first edition (in Russian), a considerable amount of experimental and theoretical material on tokamak research has been accumu lated. The new-generation devices, viz. , TFTR, JET and JT-60 were put into operation. The first experiments on these units have confirmed the correctness of the basic physical concepts underlying their construction. Experiments on plasma heating with the help of neutral beams and high-frequency (HF) waves on previous generation devices made it possible to obtain high-P plasmas. The number of "medium-size" tokamaks in operation has increased. New experi mental results and advances in the theory have led to more complicated and perfected models of high-temperature plasma. Rapid progress in computer hardware and software has played an important role in the further development of mathematical modeling. While preparing the English edition of the book, we have revised the text considerably. Several new models which have undergone significant advance ment in recent years are described. A section devoted to models of RF (radio frequency) current drive has been added to Chap. 2. The reduced magneto hydrodynamic (MHD) equations for high-P plasma are now considered in detail in Chap. 3. Chapter 4 contains the latest results on anomalous thermal conductivity, diffusion coefficient and pinching. Two new sections are added to Chap. 5.
Author: Marco Ariola
Publisher: Springer
ISBN: 9781848820081
Category : Technology & Engineering
Languages : en
Pages : 162
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Book Description
this part is supported by two useful appendices on some of the mathematical tools used and the physical units of plasma physics. State-space models, state observers, H control, and process simulations are some of the familiar techniques used by ? the authors to meet the demanding spatial control specifications for these processes; however, the research reported in the monograph is more that just simulation studies and proposals for possible future hypothetical controllers, for the authors have worked with some of the world’s leading existing tokamak facilities. Chapter 5, 8, and 9 respectively, give practical results of implementations of their control schemes on the FTU Tokamak (Italy), the TCV Tokamak (Switzerland), and the JET Tokamak (United Kingdom). Additionally, the authors present simulation results of their ideas for the control of the new tokamak proposed for the ITER project. In conclusion, being very aware that most control engineers will not be conversant with the complexities of tokamak nuclear fusion reactor control, the authors have taken special care to give a useful introduction to the background of nuclear fusion, the science of plasma physics and appropriate models in the first part of the monograph (Chapters 1 to 3). This introduction is followed by six chapters (4 to 9) of control studies. In Chapter 4, the generic control problem is established and then five case study chapters follow.
Author: Stefano Bernabei
Publisher: Compositori
ISBN:
Category : Science
Languages : en
Pages : 436
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Author: Sergei Sharapov
Publisher: CRC Press
ISBN: 1351002813
Category : Science
Languages : en
Pages : 156
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Book Description
The study of energetic particles in magnetic fusion plasmas is key to the development of next-generation "burning" plasma fusion experiments, such as the International Thermonuclear Experimental Reactor (ITER) and the Demonstration Power Station (DEMO). This book provides a comprehensive introduction and analysis of the experimental data on how fast ions behave in fusion-grade plasmas, featuring the latest ground-breaking results from world-leading machines such as the Joint European Torus (JET) and the Mega Ampere Spherical Tokamak (MAST). It also details Alfvenic instabilities, driven by energetic ions, which can cause enhanced transport of energetic ions. MHD spectroscopy of plasma via observed Alfvenic waves called "Alfvén spectroscopy" is introduced and several applications are presented. This book will be of interest to graduate students, researchers, and academics studying fusion plasma physics. Features: Provides a comprehensive overview of the field in one cohesive text, with the main physics phenomena explained qualitatively first. Authored by an authority in the field, who draws on his extensive experience of working with energetic particles in tokamak plasmas. Is suitable for extrapolating energetic particle phenomena in fusion to other plasma types, such as solar and space plasmas.
Author:
Publisher:
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Category :
Languages : en
Pages :
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Book Description
The major increase in discharge duration and plasma energy in a next-step DT [deuterium-tritium] fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety, and performance. Erosion will increase to a scale of several centimeters from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma-facing components. Controlling plasma wall interactions is critical to achieving high performance in present-day tokamaks and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena has stimulated an internationally coordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor (ITER) project and significant progress has been made in better under standing these issues. This paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next-step fusion reactors. Two main topical groups of interactions are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation, (ii) tritium retention and removal. The use of modeling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R and D [Research and Development] avenues for their resolution are presented.
Author: Wojciech R. Fundamenski
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Boundary (edge) plasma phenomena play a crucial role in the development of controlled thermonuclear fusion via magnetic confinement. In this work, the edge plasma are modeled by a coupled set of plasma/neutral transport equations; the neutral transport equations are solved by Monte-Carlo techniques (NIMBUS code), while the plasma transport equations are solved using an improved onion-skin method (OSM) based on the numerical techniques of computational fluid dynamics. The OSM approach, as defined in this thesis, consists of replacing the anomalous cross-field flux terms by (often simplified, always adjustable) cross-field source terms, and taking advantage of available diagnostic data (typically radial profiles of ã and Te from target Langmuir probes), of varying these cross-field sources in order to minimize the error between the solution and the diagnostic data. The OSM approach was shown capable of capturing the transition from attached to detached conditions in a tokamak divertor plasma, an important and timely aspect of present fusion research. The other applications presented in the thesis include a study of the sensitivity of modeling assumptions, a code-code comparison between the OSM and a standard 2D approach (represented by the EDGE2D code), and a code-experiment comparison with reciprocating probe data for Ohmic, L-mode and H-mode shots on the JET tokamak.
