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Characterization Of Mhd Activity And Its Influence On Radiation Asymmetries During Massive Gas Injection In Diii D
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Book Synopsis Characterization of MHD Activity and Its Influence on Radiation Asymmetries During Massive Gas Injection in DIII-D. by :
Download or read book Characterization of MHD Activity and Its Influence on Radiation Asymmetries During Massive Gas 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: Measurements from the DIII-D tokamak show that toroidal radiation asymmetries during fast shutdown by massive gas injection (MGI) are largely driven by n = 1 magnetohydrodynamic modes during the thermal quench. The phenomenology of these modes, which are driven unstable by pro le changes as the thermal energy is quenched, is described based on detailed magnetic measurements. Here, the toroidal evolution of the dominantly n = 1 perturbation is understood to be a function of three parameters: the location of the MGI port, pre-MGI plasma rotation, and n = 1 error elds. Here, the resulting level of radiation asymmetry in these DIII-D plasmas is modest, with a toroidal peaking factor (TPF) of 1:2 ± 0:1 for the total thermal quench energy and 1:4 ± 0:3 for the peak radiated power, both of which are below the estimated limit for ITER (TPF ≈ 2).
Book Synopsis Radiation Asymmetries During Disruptions on DIII-D Caused by Massive Gas Injection by :
Download or read book Radiation Asymmetries During Disruptions on DIII-D Caused by Massive Gas Injection written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the major challenges that the ITER tokamak will have to face during its operations are disruptions. During the last few years, it has been proven that the global consequences of a disruption can be mitigated by the injection of large quantities of impurities. But one aspect that has been difficult to study was the possibility of local effects inside the torus during such injection that could damage a portion of the device despite the global heat losses and generated currents remaining below design parameter. 3D MHD simulations show that there is a potential for large toroidal asymmetries of the radiated power during impurity injection due to the interaction between the particle injection plume and a large n=1 mode. Another aspect of 3D effects is the potential occurrence of Vertical Displacement Events (VDE), which could induce large poloidal heat load asymmetries. This potential deleterious effect of 3D phenomena has been studied on the DIII-D tokamak thanks to the implementation of a multi-location massive gas injection (MGI) system as well as new diagnostic capabilities. This study showed the existence of a correlation between the location of the n=1 mode and the local heat load on the plasma facing components but shows also that this effect is much smaller than anticipated (peaking factor of ~1.1 vs 3-4 according to the simulations). There seems to be no observable heat load on the first wall of DIII-D at the location of the impurity injection port as well as no significant radiation asymmetries whether one or 2 valves are fired. This study enabled the first attempt of mitigation of a VDE using impurity injection at different poloidal locations. The results showed a more favorable heat deposition when the VDE is mitigated early (right at the onset) by impurity injection. As a result, no significant improvement of the heat load mitigation efficiency has been observed for late particle injection whether the injection is done "in the way" of the VDE (upward VDE mitigated by injection from the upper part of the vessel vs the lower part) or not.
Book Synopsis The Role of MHD in 3D Aspects of Massive Gas Injection by :
Download or read book The Role of MHD in 3D Aspects of Massive Gas Injection written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulations of massive gas injection (MGI) for disruption mitigation in DIII-D are carried out to compare the toroidal peaking of radiated power for the cases of one and two gas jets. The radiation toroidal peaking factor (TPF) results from a combination of the distribution of impurities and the distribution of heat flux associated with then =1 mode. The injected impurities are found to spread helically along field lines preferentially toward the high-field-side, which is explained in terms of a nozzle equation. In light of this mechanism, reversing the current direction also reverses the toroidal direction of impurity spreading. During the pre-thermal quench phase of the disruption, the toroidal peaking of radiated power is reduced in the straightforward manner by increasing from one to two gas jets. However, during the thermal quench phase, reduction in the TPF is achieved only for a particular arrangement of the two gas valves with respect to the field line pitch. In particular, the relationship between the two valve locations and the 1/1 mode phase is critical, where gas valve spacing that is coherent with 1/1 symmetry effectively reduces TPF.
Book Synopsis Characterization of High Field Side MHD Activity During Local Helicity Injection by : Jessica L. Pachicano
Download or read book Characterization of High Field Side MHD Activity During Local Helicity Injection written by Jessica L. Pachicano and published by . This book was released on 2018 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Charge-exchange Measurements of MHD Activity During Neutral Beam Injection in the Princeton Large Torus and the Poloidal Divertor Experiment by :
Download or read book Charge-exchange Measurements of MHD Activity During Neutral Beam Injection in the Princeton Large Torus and the Poloidal Divertor Experiment written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The horizontally scanning, multiangle charge-exchange analyzers on the Princeton Large Torus (PLT) and the Poloidal Divertor Experiment (PDX) were used to study the effects of MHD activity on the background ion distribution function and on the beam ion slowing-down process during high-power neutral injection. Sawtooth oscillations were observed in the fast ion flux on PLT and PDX, and measurements with neutral beams providing local neutral density enhancement indicate that ions are transported radially when these events occur. With near-perpendicular injection in PDX, at the lower toroidal fields necessary to maximize beta, rapid, repetitive bursts of greatly enhanced charge-exchange flux were observed. These are associated with the ''fishbone'' MHD instability, and a substantial depletion of the perpendicular slowing-down spectrum below the injection energy was seen. A simple phenomenological model for this loss mechanism was developed, and its use in simulation codes has been successful in providing good agreement with the data. The behavior and characteristics of this model are well matched by the direct theoretical calculations.
Book Synopsis DISRUPTION MITIGATION USING HIGH-PRESSURE NOBLE GAS INJECTION ON DIII-D. by :
Download or read book DISRUPTION MITIGATION USING HIGH-PRESSURE NOBLE GAS INJECTION ON DIII-D. written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-pressure gas jet injection of neon and argon is used to mitigate the deleterious effects from tokamak disruptions. Thermal loading of the divertor surfaces, vessel stress from poloidal halo currents and the buildup and loss of relativistic electrons to the wall are all greatly reduced or eliminated. The gas jet penetrates through to the central plasma as a neutral species at its sonic velocity[approx] 300-500 m/s. The injected impurity species radiate> 95% of the plasma stored energy, accompanied by a 500-fold increase the total electron inventory in the plasma volume, thus decreasing localized heating at the divertor targets. The poloidal halo currents at the wall are reduced because of the rapid cooling and the slow movement of the plasma toward the wall during the current quench. When a sufficient quantity of gas is injected, the extremely large total (free+ bound) electron density inhibits runaway electrons in the current quench, as predicted. A physical model of radiative cooling has been developed and is validated against DIII-D experiments. The model shows that gas jet mitigation, including runaway suppression, extrapolates favorably to burning plasmas where disruption damage would be more severe. The use of real-time detection of the onset of a disruption to trigger massive gas injection and to mitigate the ensuing damage is demonstrated.
Download or read book MHD Analysis of High (. Beta written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: PBX discharges run at the lowest q and highest (.beta./sub t/) always terminated in a hard disruption. The discharges, with (.beta./sub t/) values of up to 5.5% and q-values down to 2.2, were obtained by employing large current ramps and large gas feed rates during neutral beam injection. Previous work has indicated that the achieved (.beta./sub t/)-values were consistent with the limit imposed by the n = 1 ideal external kink with a conducting wall at b/a = 2. In this work, we investigate further the validity of ideal MHD theory in explaining the low-q/sub psi/j disruptions. In particular, the character of the pre-disruption MHD activity in these low-q discharges, specifically the time scales of growth and internal and external mode structures, was compared with those determined from theoretical calculations. The results of these comparisons indicate that non-ideal effects must be considered to obtain detailed agreement between theory and experiment. 13 refs., 6 figs.
Book Synopsis Impurity Feedback Control for Enhanced Divertor and Edge Radiation in DIII-D Discharges by :
Download or read book Impurity Feedback Control for Enhanced Divertor and Edge Radiation in DIII-D Discharges written by and published by . This book was released on 1996 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Long pulse and steady state fusion ignition devices will require a significant radiated power fraction to minimize heat flux to, and sputtering of, the first wall. While impurity gases have been proposed to enhance radiation, precise control of impurity gas injection is essential to achieve an adequate radiative power fraction while maintaining good energy confinement and low central impurity concentration. We report here the first experiments in the DIII-D tokamak using feedback control of the rate of impurity gas injection. These experiments were carried out with active divertor pumping using the in-situ DIII-D cryopump. The radiated power fraction was controlled by sensing either UN edge line radiation (Ne{sup +7}) or mantle radiation from selected bolometer channels and using the DIII-D digital plasma control system to calculate radiated power real-time and generate an error signal to control an impurity gas injector valve.
Download or read book Science Abstracts written by and published by . This book was released on 1992 with total page 1228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 1993-07 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1990 with total page 936 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Magnetic Fusion Technology by : Thomas J. Dolan
Download or read book Magnetic Fusion Technology written by Thomas J. Dolan and published by Springer Science & Business Media. This book was released on 2014-02-10 with total page 816 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Fusion Technology describes the technologies that are required for successful development of nuclear fusion power plants using strong magnetic fields. These technologies include: • magnet systems, • plasma heating systems, • control systems, • energy conversion systems, • advanced materials development, • vacuum systems, • cryogenic systems, • plasma diagnostics, • safety systems, and • power plant design studies. Magnetic Fusion Technology will be useful to students and to specialists working in energy research.
Book Synopsis Government Reports Annual Index by :
Download or read book Government Reports Annual Index written by and published by . This book was released on 1992 with total page 1130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Academies of Sciences Engineering and Medicine Publisher : ISBN 13 :9780309677608 Total Pages :291 pages Book Rating :4.6/5 (776 download)
Book Synopsis Plasma Science by : National Academies of Sciences Engineering and Medicine
Download or read book Plasma Science written by National Academies of Sciences Engineering and Medicine and published by . This book was released on 2021-02-28 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Theory Of Toroidally Confined Plasmas, The (Third Edition) by : Roscoe B White
Download or read book Theory Of Toroidally Confined Plasmas, The (Third Edition) written by Roscoe B White and published by World Scientific Publishing Company. This book was released on 2013-11-18 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: This graduate level textbook develops the theory of magnetically confined plasma, with the aim of bringing the reader to the level of current research in the field of thermonuclear fusion. It begins with the basic concepts of magnetic field description, plasma equilibria and stability, and goes on to derive the equations for guiding center particle motion in an equilibrium field. Topics include linear and nonlinear ideal and resistive modes and particle transport. It is of use to workers in the field of fusion both for its wide-ranging account of tokamak physics and as a kind of handbook or formulary.This edition has been extended in a number of ways. The material on mode-particle interactions has been reformulated and much new information added, including methodology for Monte Carlo implementation of mode destabilization. These results give explicit means of carrying out mode destabilization analysis, in particular for the dangerous fishbone mode. A new chapter on cyclotron motion in toroidal geometry has been added, with comparisons of the analysis of resonances using guiding center results. A new chapter on the use of lithium lined walls has been added, a promising means of lowering the complexity and cost of full scale fusion reactors. A section on nonlocal transport has been added, including an analysis of Levy flight simulations of ion transport in the reversed field pinch in Padova, RFX.
Book Synopsis Solar Prominences by : Jean-Claude Vial
Download or read book Solar Prominences written by Jean-Claude Vial and published by Springer. This book was released on 2014-11-24 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the latest research results on solar prominences, including new developments on e.g. chirality, fine structure, magnetism, diagnostic tools and relevant solar plasma physics. In 1875 solar prominences, as seen out of the solar limb, were described by P.A. Secchi in his book Le Soleil as "gigantic pink or peach-flower coloured flames". The development of spectroscopy, coronagraphy and polarimetry brought tremendous observational advances in the twentieth century. The authors present and discuss exciting new challenges (resulting from observations made by space and ground-based telescopes in the 1990s and the first decade of the 21st century) concerning the diagnostics of prominences, their formation, their life time and their eruption along with their impact in the heliosphere (including the Earth). The book starts with a general introduction of the prominence “object” with some historical background on observations and instrumentation. In the next chapter, the various forms of prominences are described with a thorough attempt of classification. Their thermodynamic (and velocity) properties are then derived with emphasis on the methods (and their limits) used. This goes from the simplest optically thin case to the heavy radiative treatment of plasmas out of local thermodynamic equilibrium. The following chapters are devoted to the magnetic field measurements and indirect derivation. A new branch of diagnostic tools, the seismology, is presented along with some MHD basics. This allows to better understand the propagation of waves, the energy and force equilibria. Both small-scale and large-scale studies and their relationship are presented. The importance of the newly discovered cavities is stressed in the context of prominence destabilization. The issues of prominence formation and eruption, their connection with flares and Coronal Mass Ejections and their impact on the Earth are addressed on the basis of the latest results. Finally, an exciting new area of research is unveiled with the newly discovered evidence of similar manifestations in the Universe and their possible impact on the habitability of exoplanets. References to the basic physics (where necessary) are provided and the proposed web sites addresses will allow the reader to load exciting movies. The book is aimed at advanced students in astrophysics, post-graduates, solar physicists and more generally astrophysicists. Amateurs will enjoy the many new images which go with the text.
Book Synopsis Stellarator and Heliotron Devices by : Masahiro Wakatani
Download or read book Stellarator and Heliotron Devices written by Masahiro Wakatani and published by Oxford University Press, USA. This book was released on 1998 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph describes plasma physics for magnetic confinement of high temperature plasmas in nonaxisymmetric toroidal magnetic fields or stellarators. The techniques are aimed at controlling nuclear fusion for continuous energy production. While the focus is on the nonaxisymmetric toroidal field, or heliotron, developed at Kyoto University, the physics applies equally to other stellarators and axisymmetric tokamaks. The author covers all aspects of magnetic confinement, formation of magnetic surfaces, magnetohydrodynamic equilibrium and stability, single charged particle confinement, neoclassical transport and plasma heating. He also reviews recent experiments and the prospects for the next generation of devices.
