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Author : Zuoyang Chang
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (713 download)
Download or read book Observations of Fast Ion Losses Due to Toroidal Alfven Eigenmodes in TFTR. written by Zuoyang Chang and published by . This book was released on 1993 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (873 download)
Download or read book Observations of Fast Ion Losses Due to Toroidal Alfven Eigenmodes in TFTR. written by and published by . This book was released on 1993 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a tokamak, knowledge of the rate of fast ion loss is of importance in determining the energy balance of the discharge. Heating of the discharge may be diminished if losses are significant, since neutral beam ions, ICRF heating tail ions, and alpha particles all heat the plasma and may all be lost through processes which expel fast ions. In addition, a loss of fast ions which is sufficiently intense and localized may damage plasma facing components in the vacuum vessel. For these reasons, knowledge of the fast ion loss mechanisms is desirable. Loss processes for fast ions in a tokamak fit into two broad categories: single particle and collective. Single particle losses are those, such as first orbit loss, which are independent of the number of fast ions present. These have been seen in numerous instances on TFIR with DD fusion products, and are reported elsewhere. Collective losses arise when the fast ion density is sufficient to drive instabilities which then cause loss. The drive can come from ∂f{sub fi}/∂? (where f{sub fi} is the fast ion distribution function), ∂f{sub fi}/∂E, and resonances. Examples of collective instabilities include the toroidal Alfven eigenmode (TAE), the kinetic ballooning mode, alpha driven sawteeth, alpha driven fishbones, Alfven waves, and ion cyclotron waves. This paper limits itself to the presentation of observations made during what are believed to be TAEs which were excited under two conditions in TFTR: at low field (1.5 T), with neutral beam ions driving the mode, and at intermediate field (3.4 T) with the hydrogen minority ICRF tail ions driving the mode.
Author :
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ISBN 13 :
Total Pages : 806 pages
Book Rating : 4.:/5 (3 download)
Download or read book Energy Research Abstracts written by and published by . This book was released on 1994 with total page 806 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author : R. B. White
Publisher :
ISBN 13 :
Total Pages : 33 pages
Book Rating : 4.:/5 (713 download)
Download or read book Observations of Neutral Beam and ICRF Tail Ion Losses Due to Alfven Modes in TFTR. written by R. B. White and published by . This book was released on 1996 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jason Sears
Publisher :
ISBN 13 :
Total Pages : 221 pages
Book Rating : 4.:/5 (681 download)
Download or read book Measurement and Interpretation of Stable and Unstable Alfvén Eigenmodes in the Presence of Fast Ions in Alcator C-Mod written by Jason Sears and published by . This book was released on 2010 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: The stability of two types of lightly damped resonant eigenmodes in the presence of energetic ions is studied in Alcator C-Mod. Global Alfven eigenmodes (GAEs) can exist at frequencies between the continua of adjacent poloidal mode numbers to avoid strong continuum damping. Toroidicity-induced Alfven eigenmodes (TAEs) exist in gaps in the frequency continuum induced by toroidal coupling. Passing and trapped fast ions can resonantly excite AEs, which saturate at significant amplitude and redistribute the ions. There is evidence that consequent losses of D-T alpha particles could degrade the fusion burn. Unstable TAEs driven by ICRF-heated fast ions are observed in Alcator C-Mod with toroidal mode numbers of n = -4 and n = 6. Positive mode numbers indicate that modes are driven by fast ions having hollow pressure profiles, in agreement with measurements using the Compact Neutral Particle Analyzer (CNPA). In the absence of sufficient fast ion drive, eigenmodes are detected by exciting them with antennas close to the plasma boundary and monitoring the plasma frequency response with an array of magnetic probes, a method called active MHD excitation. This thesis reports for the first time that TAEs of various toroidal mode numbers are excited with a wide-toroidal-spectrum antenna and observed using a fully resolved toroidal array of probes. GAEs with n = 0 and damping rates around y/wo = -1%, and TAEs with n = 1 and damping rates around /~wo = -1.5% are observed. Rigorous calibration is applied to the magnetic probes to reject the system response of the diagnostic. Measurements demonstrate that even with a wide-spectrum antenna, the range of AEs that are accessible to the diagnostic for any particular equilibrium remains quite limited, subject to the modes' proximity to the plasma edge. A composite spectrum of observed stable and unstable modes, and the stability spectrum calculated by NOVA-K, shows that for fast ions with approximately 150 keV effective temperature, the most unstable mode number tends to be around n = -5. In comparison, the simple scaling of fast ion drive for kopi ~~ 1 predicts unstable modes around n = -8, demonstrating reasonable agreement with the measurements. Local islands of stability that are observed in the toroidal mode number spectrum and the fast ion temperature could be exploited by the strong dependence of the AE spectrum on subtle changes in equilibrium parameters to stabilize AEs in burning plasmas.
Author :
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ISBN 13 :
Total Pages : 786 pages
Book Rating : 4.:/5 (6 download)
Download or read book Nuclear Fusion written by and published by . This book was released on 2000 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (16 download)
Download or read book Observations of Beam Ion Losses in TFTR During TAE Modes and Other MHD Activity written by and published by . This book was released on 1993 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct measurements of fast NBI ion losses have been made near the outer midplane during MHD activity in TFTR. Bursts of beam ion loss are seen coincident with the TAE mode activity. Particles lost during TAE activity are lost at the full injection energy of 100 keV, and only the total efflux of fast ions changes during the mode, not the pitch angle or energy of the lost ions. Reductions in neutron source strength indicate that (approximately)10 percent of the beam ions can be lost in a single burst, with a cumulative loss of as much as 50 percent. Other MHD activity can cause large losses of beam ions, including passing ions.
Author : E. Fredrickson
Publisher :
ISBN 13 :
Total Pages : 18 pages
Book Rating : 4.:/5 (713 download)
Download or read book Observation of Modes at Frequencies Near the Second Alfven Gap in TFTR. written by E. Fredrickson and published by . This book was released on 2000 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : International Atomic Energy Agency
Publisher :
ISBN 13 : 9789201037954
Total Pages : 754 pages
Book Rating : 4.0/5 (379 download)
Download or read book Plasma Physics and Controlled Nuclear Fusion Research, 1994 written by International Atomic Energy Agency and published by . This book was released on 1995 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the Fifteenth International Conference held in Seville, 26 September to 1 October 1994. The conference was characterized by valuable scientific results on virtually all aspects of controlled fusion and fusion technology, laying a solid foundation for continued progress. The proceedings include all the technical papers, the pertinent discussions, and five conference summaries which are published as a separate volume.
Author : Sergei Sharapov
Publisher : CRC Press
ISBN 13 : 1351002813
Total Pages : 156 pages
Book Rating : 4.3/5 (51 download)
Download or read book Energetic Particles in Tokamak Plasmas written by Sergei Sharapov and published by CRC Press. This book was released on 2021-04-02 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : E. Fredrickson
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (713 download)
Download or read book Observation of New Branch of Toroidal Alfven Eigenmodes in TFTR. written by E. Fredrickson and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 1226 pages
Book Rating : 4.3/5 (91 download)
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1994 with total page 1226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 30 pages
Book Rating : 4.:/5 (871 download)
Download or read book Alfven Frequency Modes at the Edge of TFTR Plasmas written by and published by . This book was released on 1995 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: An Alfven frequency mode (AFM) is very often seen in TFTR neutral beam heated plasmas as well as ohmic plasmas. This quasi-coherent mode is so far only seen on the magnetic fluctuation diagnostics (Mirnov coils). A close correlation between the plasma edge density and the mode activity (frequency and amplitude) has been observed, which indicates that the AFM is an edge localized mode with r/a> 0.85. No direct impact of this mode on the plasma global performance or fast ion loss (e.g., the [alpha]-particles in DT experiments) has been observed. This mode is apparently not the conventional TAE (toroidicity-induced Alfven eigenmodes). The present TAE theory cannot explain the observation. Other possible explanations are discussed.
Author : R. B. White
Publisher :
ISBN 13 :
Total Pages : 33 pages
Book Rating : 4.:/5 (713 download)
Download or read book Observations of Neutral Beam and ICRF Tail Ion Losses Due to Alfven Modes in TFTR. written by R. B. White and published by . This book was released on 1996 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
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ISBN 13 :
Total Pages : 245 pages
Book Rating : 4.:/5 (727 download)
Download or read book On The Anomalous Fast Ion Energy Diffusion in Toroidal Plasmas Due to Cavity Modes written by and published by . This book was released on 2010 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: An enormous wave-particle diffusion coefficient along paths suitable for alpha channeling had been deduced in mode converted ion Bernstein wave experiments on Tokamak Fusion Test Reactor (TFTR) the only plausible explanation advanced for such a large diffusion coefficient was the excitation of internal cavity modes which induce particle diffusion along identical diffusion paths, but at much higher rates. Although such a mode was conjectured, it was never observed. However, recent detailed observations of high frequency compressional Alfven eigenmodes (CAEs) on the National Spherical torus Experiment (NSTX) indirectly support the existence of the related conjectured modes on TFTR. The eigenmodes responsible for the high frequency magnetic activity can be identified as CAEs through the polarization of the observed magnetic field oscillations in NSTX and through a comparison with the theoretically derived freuency dispersion relation. Here, we show how these recent observations of high frequency CAEs lend support to this explanation of the long-standing puzzle of anomalous fast ion energy diffusion on TFTR. The support of the conjecure that these internal modes could have caused the remarkable ion energy diffusion on TFTR carries significant and favorable implications for the possibilities in achieving the alpha channeling effect with small injected power in a tokamak reactor.
Download or read book Resonant Toroidal Alfven Eigenmodes (RTAEs) in Neutral Beam Heated Reverse Magnetic Shear Plasmas on TFTR. written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Resonant Toroidal Alfven Eigenmodes (RTAEs) [1, 2] excited by neutral beam ions are observed in the region of the internal transport barrier in enhanced reverse shear (ERS) plasmas on TFTR. These modes occur in multiples of the same toroidal mode number in the range n=2-4 and appear as highly localized structures near the minimum in the q-profile with frequency near to that expected for TAEs. Unlike regular TAEs, these modes are observed in plasmas where the birth velocity of beam ions is well below the fundamental or sideband resonance condition. Theoretical analysis indicates that the Toroidicity induced Alfven Eigenmode (TAE) does not exist in these discharges due to strong pressure gradients (of the thermal and fast ions) which moves the mode frequency down into the lower Alfven continuum. However a new non-perturbative analysis (where the energetic particles are allowed to modify the mode frequency and mode structure) indicates that RTAEs can be driven by neutral beam ions in the weak magnetic shear region of ERS plasma, consistent with observations on TFTR. The importance of such modes is that they may affect the alpha particle heating profile or enhance the loss of energetic alpha particles in an advanced tokamak reactor where large internal pressure gradients and reverse magnetic shear operation are required to sustain large bootstrap current.
Author : D. S. Darrow
Publisher :
ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (713 download)
Download or read book Observations of Beam Ion Losses in TFTR During TAE Modes and Other MHD Activity written by D. S. Darrow and published by . This book was released on 1993 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
