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 (
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.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book U S Department of Energy Performance and Accountability Report Fiscal Year 2002 written by and published by DIANE Publishing. This book was released on with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Magnetic Fusion Energy written by George Neilson and published by Woodhead Publishing. This book was released on 2016-06-02 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Fusion Energy: From Experiments to Power Plants is a timely exploration of the field, giving readers an understanding of the experiments that brought us to the threshold of the ITER era, as well as the physics and technology research needed to take us beyond ITER to commercial fusion power plants. With the start of ITER construction, the world’s magnetic fusion energy (MFE) enterprise has begun a new era. The ITER scientific and technical (S&T) basis is the result of research on many fusion plasma physics experiments over a period of decades. Besides ITER, the scope of fusion research must be broadened to create the S&T basis for practical fusion power plants, systems that will continuously convert the energy released from a burning plasma to usable electricity, operating for years with only occasional interruptions for scheduled maintenance. Provides researchers in academia and industry with an authoritative overview of the significant fusion energy experiments Considers the pathway towards future development of magnetic fusion energy power plants Contains experts contributions from editors and others who are well known in the field
Download or read book Energy and Water and Related Agencies Appropriations for Fiscal Year 2007 written by United States. Congress. Senate. Committee on Appropriations. Subcommittee on Energy and Water, and Related Agencies and published by . This book was released on 2006 with total page 1800 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy and Water Development Appropriations for 2007 written by United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development and published by . This book was released on 2006 with total page 1782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy and Water and Related Agencies Appropriations for Fiscal Year written by United States. Congress. Senate. Committee on Appropriations and published by . This book was released on 2007 with total page 1800 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the 12th International Conference on Soft Computing for Problem Solving written by Millie Pant and published by Springer Nature. This book was released on with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fusion Technology 1996 written by C. Varandas and published by Elsevier. This book was released on 2012-12-02 with total page 1057 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of these proceedings was to provide a platform for the exchange of information on the design, construction and operation of fusion experiments. The technology which is being developed for the next step devices and fusion reactors was also covered.
Download or read book Proceedings of the Fifteenth Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating written by John Lohr and published by World Scientific. This book was released on 2009 with total page 583 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings present the latest results in electron cyclotron emission, heating and current drive, with an emphasis on the physics and technology of Electron Cyclotron Emission, Electron Cyclotron Heating and Electron Cyclotron Current Drive applied to magnetic fusion research. The field is a key element in the development of fusion power and the ITER project now under construction.
Download or read book Electron Cyclotron Emission And Electron Cyclotron Resonance Heating Ec 15 Proceedings Of The 15th Joint Workshop With Cd rom written by John Lohr and published by World Scientific. This book was released on 2009-04-15 with total page 583 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings present the latest results in electron cyclotron emission, heating and current drive, with an emphasis on the physics and technology of Electron Cyclotron Emission, Electron Cyclotron Heating and Electron Cyclotron Current Drive applied to magnetic fusion research. The field is a key element in the development of fusion power and the ITER project now under construction.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Energy and Water Development Appropriations for 2006 written by United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development and published by . This book was released on 2005 with total page 1934 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy and Water Development Appropriations for 2006 Dept of the Army Corps of Engineers written by United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development and published by . This book was released on 2005 with total page 1928 pages. Available in PDF, EPUB and Kindle. Book excerpt:
