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Disruption Mitigation Studies In Diii D
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Book Synopsis Disruption Mitigation Studies in DIII-D. by :
Download or read book Disruption Mitigation Studies in DIII-D. written by and published by . This book was released on 1999 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Data on the discharge behavior, thermal loads, halo currents, and runaway electrons have been obtained in disruptions on the DIII-D tokamak. These experiments have also evaluated techniques to mitigate the disruptions while minimizing runaway electron production. Experiments injecting cryogenic impurity killer pellets of neon and argon and massive amounts of helium gas have successfully reduced these disruption effects. The halo current generation, scaling, and mitigation are understood and are in good agreement with predictions of a semianalytic model. Results from killer pellet injection have been used to benchmark theoretical models of the pellet ablation and energy loss. Runaway electrons are often generated by the pellets and new runaway generation mechanisms, modifications of the standard Dreicer process, have been found to explain the runaways. Experiments with the massive helium gas puff have also effectively mitigated disruptions without the formation of runaway electrons that can occur with killer pellets.
Book Synopsis DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation by : D. Gray
Download or read book DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation written by D. Gray and published by . This book was released on 2006 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Injection of massive quantities of gas is a promising technique for fast shutdown of ITER for the purpose of avoiding divertor and first wall damage from disruptions. Previous experiments using massive gas injection (MGI) to terminate discharges in the DIII-D tokamak have demonstrated rapid shutdown with reduced wall heating and halo currents (relative to natural disruptions) and with very small runaway electron (RE) generation [1]. Figure 1 shows time traces which give an overview of shutdown time scales. Typically, of order 5 x 10{sup 22} Ar neutrals are fired over a pulse of 25 ms duration into stationary (non-disrupting) discharges. The observed results are consistent with the following scenario: within several ms of the jet trigger, sufficient Ar neutrals are delivered to the plasma to cause the edge temperature to collapse, initiating the inward propagation of a cold front. The exit flow of the jet [Fig. 1(a)] has a {approx} 9 ms rise time; so the quantity of neutrals which initiates the edge collapse is small (10{sup 20}). When the cold front reaches q {approx} 2 surface, global magnetohydrodynamic (MHD) modes are destabilized [2], mixing hot core plasma with edge impurities. Here, q is the safety factor. Most (90%) of the plasma thermal energy is lost via impurity radiation during this thermal quench (TQ) phase. Conducted heat loads to the wall are low because of the cold edge temperature. After the TQ, the plasma is very cold (of order several eV), so conducted wall (halo) currents are low, even if the current channel contacts the wall. The plasma current profile broadens and begins decaying resistively. The decaying current generates a toroidal electric field which can accelerate REs; however, RE beam formation appears to be limited in MGI shutdowns. Presently, it is thought that the conducted heat flux and halo current mitigation qualities of the MGI shutdown technique will scale well to a reactor-sized tokamak. However, because of the larger RE gain from avalanching and the presence of a RE seed population due to Compton-scattered fast electrons, it is possible that a RE beam can be formed well into the CQ, after the flux surfaces initially destroyed by the TQ MHD have had time to heal. Crucial MGI issues to be studied in present devices are therefore the formation, amplification, and transport of RE and the transport of impurities into the core plasma (important because the presence of impurities can, via collisional drag, help suppress RE amplification). In the study of impurity transport, both neutral delivery (directly driven into the core by the jet pressure) and ion delivery (mixed into the core by MHD) are of interest, as both contribute to RE drag. Here, three new results relevant to RE suppression from MGI are presented: (1) evidence is presented that neutral jet propagation is stopped by toroidal magnetic field pressure, (2) MGI appears to cause the CQ to begin before sufficient impurities have been injected for complete collisional suppression of RE, and (3) flux surface destruction over the region q {le} 2 occurs during the TQ. The first result suggests that neutrals cannot be delivered to the core of large tokamak discharges by MGI, even during the CQ. The second result indicates that (at least for argon MGI in DIII-D), insufficient impurities (either neutral or ion) are delivered for collisional suppression of RE at the start of the CQ. The last result suggests that the destruction of good field lines resulting from MGI is quite extensive and should be sufficient to prevent RE formation, at least at the start of the CQ.
Book Synopsis Nuremberg - Still an Open Chapter of History by : Polen Ministerstwo Sprawiedliwości
Download or read book Nuremberg - Still an Open Chapter of History written by Polen Ministerstwo Sprawiedliwości and published by . This book was released on 1980 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation by :
Download or read book DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation written by and published by . This book was released on 2006 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Injection of massive quantities of gas is a promising technique for fast shutdown of ITER for the purpose of avoiding divertor and first wall damage from disruptions. Previous experiments using massive gas injection (MGI) to terminate discharges in the DIII-D tokamak have demonstrated rapid shutdown with reduced wall heating and halo currents (relative to natural disruptions) and with very small runaway electron (RE) generation [1]. Figure 1 shows time traces which give an overview of shutdown time scales. Typically, of order 5 x 1022 Ar neutrals are fired over a pulse of 25 ms duration into stationary (non-disrupting) discharges. The observed results are consistent with the following scenario: within several ms of the jet trigger, sufficient Ar neutrals are delivered to the plasma to cause the edge temperature to collapse, initiating the inward propagation of a cold front. The exit flow of the jet [Fig. 1(a)] has a (almost equal to) 9 ms rise time; so the quantity of neutrals which initiates the edge collapse is small (102°). When the cold front reaches q (almost equal to) 2 surface, global magnetohydrodynamic (MHD) modes are destabilized [2], mixing hot core plasma with edge impurities. Here, q is the safety factor. Most (90%) of the plasma thermal energy is lost via impurity radiation during this thermal quench (TQ) phase. Conducted heat loads to the wall are low because of the cold edge temperature. After the TQ, the plasma is very cold (of order several eV), so conducted wall (halo) currents are low, even if the current channel contacts the wall. The plasma current profile broadens and begins decaying resistively. The decaying current generates a toroidal electric field which can accelerate REs; however, RE beam formation appears to be limited in MGI shutdowns. Presently, it is thought that the conducted heat flux and halo current mitigation qualities of the MGI shutdown technique will scale well to a reactor-sized tokamak. However, because of the larger RE gain from avalanching and the presence of a RE seed population due to Compton-scattered fast electrons, it is possible that a RE beam can be formed well into the CQ, after the flux surfaces initially destroyed by the TQ MHD have had time to heal. Crucial MGI issues to be studied in present devices are therefore the formation, amplification, and transport of RE and the transport of impurities into the core plasma (important because the presence of impurities can, via collisional drag, help suppress RE amplification). In the study of impurity transport, both neutral delivery (directly driven into the core by the jet pressure) and ion delivery (mixed into the core by MHD) are of interest, as both contribute to RE drag.
Book Synopsis RESEARCH PROGRESS AND HARDWARE SYSTEMS AT DIII-D. by : P. I. PETERSEN
Download or read book RESEARCH PROGRESS AND HARDWARE SYSTEMS AT DIII-D. written by P. I. PETERSEN and published by . This book was released on 2003 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 During the last two years significant progress has been made in the scientific understanding of DIII-D plasmas. Much of this progress has been enabled by the addition of new hardware systems. The electron cyclotron (EC) system has been upgraded from 3 MW to 6 MW, by adding three 1 MW gyrotrons with diamond windows and three steerable launchers (PPPL). The new gyrotrons have been tested to 1.0 MW for 5 s. The system has been used to control the 3/2 and 2/1 neoclassical tearing modes and to locally heat the plasma and thereby indirectly control the current density. Electron cyclotron current drive ECCD has been used to directly affect the current density. A Li-beam diagnostic has been brought on-line for measuring the edge current density using Zeeman splitting. A set of 12 coils (1-coils), consisting of six picture frame coils each above and below the midplane, with a capability of 7 kA for 10 s has been installed inside the DIII-D vessel. These coils, along with the existing six C-coils, are used to apply non-axisymmetric fields to the plasma for both exciting and controlling plasma instabilities. The DIII-D digital plasma control system is now used to not just control the shape and location of the plasma but also the electron temperature, density, the NTMs, RWMs, plasma beta and disruption mitigation. Plasma disruption experiments are extended to mitigation of real time detected disruptions on DIII-D.
Book Synopsis Active Control of Magneto-hydrodynamic Instabilities in Hot Plasmas by : Valentin Igochine
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.
Book Synopsis DIII-D Disruption Experiment Results by :
Download or read book DIII-D Disruption Experiment Results written by and published by . This book was released on 1995 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tokamak discharges are frequently ended by disruptions, an instability leading to a very sudden termination of the plasma. Although numerous studies of disruptions have been made, critical data is still needed to develop theoretical models for fundamental aspects of the disruption. This paper describes simultaneous profile measurements of the current, temperature, and density during the disruptive phase of a beam heated single-null divertor discharge in the DIII-D tokamak. The stored energy is lost early in the first phase of the disruption (thermal quench) after which the central temperature is a few hundred eV, and following the start of the current decay (current quench) the temperature has fallen to 100 eV. The current profile measured using the Motional Stark Effect (MSE) diagnostic is observed to flatten rapidly (
Book Synopsis Disruption Mitigation Using High Pressure Gas Jets by :
Download or read book Disruption Mitigation Using High Pressure Gas Jets written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research is to establish credible disruption mitigation scenarios based on the technique of massive gas injection. Disruption mitigation seeks to minimize or eliminate damage to internal components that can occur due to the rapid dissipation of thermal and magnetic energy during a tokamak disruption. In particular, the focus of present research is extrapolating mitigation techniques to burning plasma experiments such as ITER, where disruption-caused damage poses a serious threat to the lifetime of internal vessel components. A majority of effort has focused on national and international collaborative research with large tokamaks: DIII-D, Alcator C-Mod, JET, and ASDEX Upgrade. The research was oriented towards empirical trials of gas-jet mitigation on several tokamaks, with the goal of developing and applying cohesive models to the data across devices. Disruption mitigation using gas jet injection has proven to be a viable candidate for avoiding or minimizing damage to internal components in burning plasma experiments like ITER. The physics understanding is progress towards a technological design for the required gas injection system in ITER.
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.
Author :National Academies of Sciences, Engineering, and Medicine Publisher :National Academies Press ISBN 13 :0309487463 Total Pages :341 pages Book Rating :4.3/5 (94 download)
Book Synopsis Final Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research by : National Academies of Sciences, Engineering, and Medicine
Download or read book Final Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-05-31 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fusion offers the prospect of virtually unlimited energy. The United States and many nations around the world have made enormous progress toward achieving fusion energy. With ITER scheduled to go online within a decade and demonstrate controlled fusion ten years later, now is the right time for the United States to develop plans to benefit from its investment in burning plasma research and take steps to develop fusion electricity for the nation's future energy needs. At the request of the Department of Energy, the National Academies of Sciences, Engineering, and Medicine organized a committee to develop a strategic plan for U.S. fusion research. The final report's two main recommendations are: (1) The United States should remain an ITER partner as the most cost-effective way to gain experience with a burning plasma at the scale of a power plant. (2) The United States should start a national program of accompanying research and technology leading to the construction of a compact pilot plant that produces electricity from fusion at the lowest possible capital cost.
Book Synopsis Self-consistent Modeling of Plasma Response to Impurity Spreading from Intense Localized Source by : Mikhail Koltunov
Download or read book Self-consistent Modeling of Plasma Response to Impurity Spreading from Intense Localized Source written by Mikhail Koltunov and published by Forschungszentrum Jülich. This book was released on 2012 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Investigations and Oversight Publisher : ISBN 13 : Total Pages :820 pages Book Rating :4.0/5 ( download)
Book Synopsis Fusion Energy Program by : United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Investigations and Oversight
Download or read book Fusion Energy Program written by United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Investigations and Oversight and published by . This book was released on 1990 with total page 820 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak by : T. C. Luce
Download or read book Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak written by T. C. Luce and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q {approx} 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.
Book Synopsis Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak by :
Download or read book Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q (almost equal to) 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.
Book Synopsis DIII-D Accomplishments and Plans in Support of Fusion Next Steps by :
Download or read book DIII-D Accomplishments and Plans in Support of Fusion Next Steps written by and published by . This book was released on 2013 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: DIII-D is using its flexibility and diagnostics to address the critical science required to enable next step fusion devices. We have adapted operating scenarios for ITER to low torque and are now being optimized for transport. Three ELM mitigation scenarios have been developed to near-ITER parameters. New control techniques are managing the most challenging plasma instabilities. Disruption mitigation tools show promising dissipation strategies for runaway electrons and heat load. An off axis neutral beam upgrade has enabled sustainment of high [beta]N capable steady state regimes. Divertor research is identifying the challenge, physics and candidate solutions for handling the hot plasma exhaust with notable progress in heat flux reduction using the snowflake configuration. Our work is helping optimize design choices and prepare the scientific tools for operation in ITER, and resolve key elements of the plasma configuration and divertor solution for an FNSF.
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.
Author :United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development Publisher : ISBN 13 : Total Pages :956 pages Book Rating :4.F/5 ( download)
Book Synopsis Energy and Water Development Appropriations for 2015: Department of Energy: Secretary of Energy by : United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development
Download or read book Energy and Water Development Appropriations for 2015: Department of Energy: Secretary of Energy written by United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development and published by . This book was released on 2014 with total page 956 pages. Available in PDF, EPUB and Kindle. Book excerpt:
