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Author: Rebecca Lee Masline Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
In this dissertation, we investigate two proposed features aimed at improving the performance of the divertor exhaust system in tokamak nuclear fusion devices. Specifically, we assess the influence of the "inverse" plasma sheath and long-leg divertor configurations on the divertor plasma using numerical simulations. First, we investigate the "inverse" plasma sheath, which has been suggested to prevent the flow of ions to the wall and promote divertor detachment. We use the UEDGE code to simulate the physics of both the inverse and standard (Bohm) sheath regime at the divertor targets. Our results show little difference in the overall plasma state, but an increase in electron heat flux to the divertor targets. Additionally, we observe a bifurcation behavior related to plasma recombination effects, and present an analytical model of this behavior. Second, we evaluate the long outer divertor leg, which is designed to increase volumetric dissipation, enhance turbulence spreading, and extend the distance between the material surface and the fragile core plasma. Using the SOLPS4.3 code, we assess the transition to the detached divertor regime, with scans on plasma density, transport coefficients, and multiple impurity species. Our results show a significant contribution to the energy balance from cross-field transport to the side walls and considerable recycling of impurities along the long leg, enabling delocalization of the radiated heat flux. Overall, this dissertation provides important insights into the physics associated with these proposed divertor features. The results suggest that the inverse plasma sheath may not have a significant impact on divertor plasma detachment, while the long-leg divertor configuration has potential to improve divertor performance by reducing impurity radiation localization and enhancing energy dissipation through cross-field transport. These findings contribute to the ongoing efforts to develop more efficient and effective divertor exhaust systems for tokamak fusion devices.
Author: Rebecca Lee Masline Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
In this dissertation, we investigate two proposed features aimed at improving the performance of the divertor exhaust system in tokamak nuclear fusion devices. Specifically, we assess the influence of the "inverse" plasma sheath and long-leg divertor configurations on the divertor plasma using numerical simulations. First, we investigate the "inverse" plasma sheath, which has been suggested to prevent the flow of ions to the wall and promote divertor detachment. We use the UEDGE code to simulate the physics of both the inverse and standard (Bohm) sheath regime at the divertor targets. Our results show little difference in the overall plasma state, but an increase in electron heat flux to the divertor targets. Additionally, we observe a bifurcation behavior related to plasma recombination effects, and present an analytical model of this behavior. Second, we evaluate the long outer divertor leg, which is designed to increase volumetric dissipation, enhance turbulence spreading, and extend the distance between the material surface and the fragile core plasma. Using the SOLPS4.3 code, we assess the transition to the detached divertor regime, with scans on plasma density, transport coefficients, and multiple impurity species. Our results show a significant contribution to the energy balance from cross-field transport to the side walls and considerable recycling of impurities along the long leg, enabling delocalization of the radiated heat flux. Overall, this dissertation provides important insights into the physics associated with these proposed divertor features. The results suggest that the inverse plasma sheath may not have a significant impact on divertor plasma detachment, while the long-leg divertor configuration has potential to improve divertor performance by reducing impurity radiation localization and enhancing energy dissipation through cross-field transport. These findings contribute to the ongoing efforts to develop more efficient and effective divertor exhaust systems for tokamak fusion devices.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
Indications that flows in the divertor can exhibit complex behavior have been obtained from 2-D modeling but so far remain mostly unconfirmed by experiment. An important feature of flow physics is that of flow reversal. Flow reversal has been predicted analytically and it is expected when the ionization source arising from neutral or impurity ionization in the divertor region is large, creating a high pressure zone. Plasma flows arise to equilibrate the pressure. A radiative divertor regime has been proposed in order to reduce the heat and particle fluxes to the divertor target plates. In this regime, the energy and momentum of the plasma are dissipated into neutral gas introduced in the divertor region, cooling the plasma by collisional, radiative and other atomic processes so that the plasma becomes detached from the target plates. These regimes have been the subject of extensive studies in DIII-D to evaluate their energy and particle transport properties, but only recently it has been proposed that the energy transport over large regions of the divertor must be dominated by convection instead of conduction. It is therefore important to understand the role of the plasma conditions and geometry on determining the region of convection-dominated plasma in order to properly control the heat and particle fluxes to the target plates and hence, divertor performance. The authors have observed complex structures in the deuterium ion flows in the DIII-D divertor. Features observed include reverse flow, convective flow over a large volume of the divertor and stagnant flow. They have measured large gradients in the plasma potential across the separatrix in the divertor and determined that these gradients induce poloidal flows that can potentially affect the particle balance in the divertor.
Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
Because the radiation power density from a marfe scales approximately as the square of its plasma pressure, and since increased radiation would aid divertor detachment for high power tokamaks, this paper identifies regions that might permit locally increased plasma pressure in steady state. The magnetic and dynamic (flow) constraints of magneto-hydrodynamics (MHD) are examined for self-consistent locally increased pressure equilibria, in both the magnetically open tokamak scrape-off layer (SOL) and the closed surfaces just inside the last closed flux surface. In most tokamak geometries it is difficult to recycle particles at a sufficient rate to sustain high pressure marfes, but they might be possible near a divertor X-point.
Author: P.C Stangeby Publisher: CRC Press ISBN: 9780750305594 Category : Science Languages : en Pages : 738
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: MITSURU KIKUCHI Publisher: International Atomic Energy ISBN: Category : Antiques & Collectibles Languages : en Pages : 1158
Book Description
Humans do not live by bread alone. Physically we are puny creatures with limited prowess, but with unlimited dreams. We see a mountain and want to move it to carve out a path for ourselves. We see a river and want to tame it so that it irrigates our fields. We see a star and want to fly to its planets to secure a future for our progeny. For all this, we need a genie who will do our bidding at a flip of our fingers. Energy is such a genie. Modern humans need energy and lots of it to live a life of comfort. In fact, the quality of life in different regions of the world can be directly correlated with the per capita use of energy [1.1–1.5]. In this regard, the human development index (HDI) of various countries based on various reports by the United Nations Development Programme (UNDP) [1.6] (Fig. 1.1), which is a parameter measuring the quality of life in a given part of the world, is directly determined by the amount of per capita electricity consumption. Most of the developing world (~5 billion people) is crawling up the UN curve of HDI versus per capita electricity consumption, from abysmally low values of today towards the average of the whole world and eventually towards the average of the developed world. This translates into a massive energy hunger for the globe as a whole. It has been estimated that by the year 2050, the global electricity demand will go up by a factor of up to 3 in a high growth scenario [1.7–1.9]. The requirements beyond 2050 go up even higher.
Author: Fulvio Militello Publisher: Springer Nature ISBN: 3031173392 Category : Science Languages : en Pages : 534
Book Description
This book serves as an introduction to boundary plasma physics, providing an accessible entry point to the topic of plasma exhaust in magnetic confinement devices. While it delivers a concise, rigorous, and comprehensive account of all the major scientific topics relevant to those working on the subject, it also remains accessible and easy to consult due to its modular and compact structure. Beginning with the basic kinetic and fluid descriptions of plasma, and advancing through plasma-surface interactions, filamentary transport and plasma detachment, to conclude with a discussion of divertor configurations, this book represents a necessary and timely addition to the literature on the fast-growing field of boundary plasma physics. It will appeal to experienced theoreticians or experimentalists looking to enter the field as well as graduate students wishing to learn about it.
Author: Pablo Martín Publisher: Springer Science & Business Media ISBN: 9780792355274 Category : Science Languages : en Pages : 1080
Book Description
This book contains a broad spectrum of plasma physics areas, from magnetic confinement (tokamaks) to spectroscopy in plasmas. The invited papers of the LAWPP present mini-courses for graduate students and review papers in each area, also updating the new ideas in the field.
Author: Giuseppe Gorini Publisher: Springer Science & Business Media ISBN: 1461303699 Category : Science Languages : en Pages : 631
Book Description
This book of proceedings collects the papers presented at the Workshop on Diagnostics for ITER, held at Villa Monastero, Varenna (Italy), from August 28 to September 1, 1995. The Workshop was organised by the International School of Plasma Physics "Piero Caldirola. " Established in 1971, the ISPP has organised over fifty advanced courses and workshops on topics mainly related to plasma physics. In particular, courses and workshops on plasma diagnostics (previously held in 1975, 1978, 1982, 1986, and 1991) can be considered milestones in the history of this institution. Looking back at the proceedings of the previous meetings in Varenna, one can appreciate the rapid progress in the field of plasma diagnostics over the past 20 years. The 1995 workshop was co-organised by the Istituto di Fisica del Plasma of the National Research Council (CNR). In contrast to previous Varenna meetings on diagnostics, which have covered diagnostics in present-day tokamaks and which have had a substantial tutorial component, the 1995 workshop concentrated specifically on the problems and challenges of ITER diagnostics. ITER (the International Thennonuclear Experimental Reactor, a joint venture of Europe, Japan, Russia, and the United States, presently under design) will need to measure a wide range of plasma parameters in order to reach and sustain high levels of fusion power. A list of the measurement requirements together with the parameter ranges, target measurement resolutions, and accuracies provides the starting point for selecting a list of candidate diagnostic systems.
Author: C.H. Wu Publisher: Springer Science & Business Media ISBN: 9401143315 Category : Technology & Engineering Languages : en Pages : 351
Book Description
One of the most important issues in the construction of future magnetic confinement fusion machines is that of the materials of which they are constructed, and one of the key points of proper material choice is the recycle of hydrogen isotopes with materials at the plasma face. Tritium machines demand high safety and economy, which in turn requires the lowest possible T inventory and smallest possible permeation through the plasma facing materials. The recycle behaviour of the in-vessel components must also be known if the plasma reaction is to predictable and controllable, and finally, the fuel cycle and plasma operating regimes may be actively controlled by special materials and methods. The book discusses both laboratory experiments exploring the basic properties of non-equilibrium hydrogen-solid systems (diffusion, absorption, boundary processes) and experimental results obtained from existing fusion machines under conditions simulating future situations to some extent. Contributions are from experts in the fields of nuclear fusion, materials science, surface science, vacuum science and technology, and solid state physics.
Author: Rebecca Lee Masline
Author: Rebecca Lee Masline
Author: 
Author: 
Author: P.C Stangeby
Author: MITSURU KIKUCHI
Author: Fulvio Militello
Author: Pablo Martín
Author: S. I. Krasheninnikov
Author: Giuseppe Gorini
Author: C.H. Wu