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Existence of core localized toroidicity-induced Alfven eigenmode

Description: The core-localized toroidicity-induced Alfven eigenmode (TAE) is shown to exist at finite plasma pressure due to finite aspect ratio effects in tokamak plasma. The new critical beta for the existence of the TAE mode is given by {alpha}{approx} 3{epsilon} + 2s{sup 2}, where {epsilon} = r/R is the inverse aspect ratio, s is the magnetic shear and {alpha} = -Rq{sup 2}d{beta}/dr is the normalized pressure gradient. In contrast, previous critical {alpha} is given by {alpha} {approx} s{sup 2}. In the… more
Date: February 1, 1995
Creator: Fu, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Energetic Particle-induced Geodesic Acoustic Mode

Description: A new energetic particle-induced Geodesic Acoustic Mode (EGAM) is shown to exist. The mode frequency, mode structure, and mode destabilization are determined non-perturbatively by energetic particle kinetic effects. In particular the EGAM frequency is found to be substantially lower than the standard GAM frequency. The radial mode width is determined by the energetic particle drift orbit width and can be fairly large for high energetic particle pressure and large safety factor. These results ar… more
Date: September 12, 2008
Creator: Fu, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Excitation of high-n toroidicity-induced shear Alfven eigenmodes by energetic particles and fusion alpha particles in tokamaks

Description: The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using t… more
Date: July 1, 1992
Creator: Fu, G. Y. & Cheng, C. Z.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Toroidal Alfven wave stability in ignited tokamaks

Description: The effects of fusion-product alpha particles on the stability of global-type shear Alfven waves in an ignited tokamak plasma are investigated in toroidal geometry. Finite toroidicity can lead to stabilization of the global Alfven eigenmodes, but it induces a new global shear Alfven eigenmodes, which is strongly destabilized via transit resonance with alpha particles. 8 refs., 2 figs.
Date: January 1, 1989
Creator: Cheng, C. Z.; Fu, G. Y. & Van Dam, J. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Excitation of high-n toroidicity-induced shear Alfven eigenmodes by energetic particles and fusion alpha particles in tokamaks

Description: The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using t… more
Date: July 1, 1992
Creator: Fu, G. Y. & Cheng, C. Z.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Vertical Stability in a Current-carrying Stellarator

Description: An analytic stability criterion is derived for the vertical mode in a large aspect ratio stellarator. The effects of vacuum magnetic field generated by helical coils are shown to be stabilizing due to enhancement of field line bending energy. For wall at infinite distance from the plasma, the amount of external poloidal flux needed for stabilization is given by f = [k(subscript 2)-K]/[K(subscript 2) + 1] where k is the axisymmetric elongation and f is the ratio of vacuum rotational transform to… more
Date: October 1, 1999
Creator: FU, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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On Nonlinear Self-interaction of Geodesic Acoustic Mode Driven By Energetic Particles

Description: It is shown that nonlinear self-interaction of energetic particle-driven Geodesic Acoustic Mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and ener… more
Date: October 1, 2010
Creator: Fu, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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On Nonlinear Self-interaction of Geodesic Acoustic Mode Driven by Energetic Particles

Description: It is shown that nonlinear self-interaction of energetic particle-driven Geodesic Acoustic Mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and ener… more
Date: June 4, 2010
Creator: Fu, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Stability of the toroidicity-induced Alfven eigenmode in axisymmetric toroidal equilibria

Description: The stability of toroidicity-induced Alfven eigenmodes (TAE) is investigated in general tokamak equilibria with finite aspect ratio and finite plasma beta. The finite orbit width of the hot particles and the collisional damping of the trapped electrons are included. For the trapped hot particles, the finite orbit width is found to be stabilizing. For the circulating hot particles, the finite orbit width effect is stabilizing for larger values of v{sub h}/v{sub A} (> 1) and destabilizing for sma… more
Date: September 1, 1993
Creator: Fu, G. Y.; Cheng, C. Z. & Wong, K. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Kinetic Damping of Toroidal Alfven Eigenmodes

Description: The damping of Toroidal Alfven Eigenmodes in JET plasmas is investigated by using a reduced kinetic model. Typically no significant damping is found to occur near the center of the plasma due to mode conversion to kinetic Alfven waves. In contrast, continuum damping from resonance near the plasma edge may be significant, and when it is, it gives rise to damping rates that are compatible with the experimental observations.
Date: May 3, 2005
Creator: Fu, G. Y.; Berk, H. L. & Pletzer, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Recent progress in linear and nonlinear studies of toroidal Alfven eigenmode

Description: TAE modes are studied in linear and nonlinear regimes using several kinetic/MHD hybrid models. It is shown that the stability of TAE mode is largely determined by its radial mode structure. The calculated stability thresholds are correlated well with observations, including the recently observed alpha-driven TAE modes in the TFTR DT experiments. In the nonlinear regime, quasilinear simulations with multiple modes show that the saturation level is enhanced by nonlinear wave-particle resonance ov… more
Date: May 1, 1997
Creator: Fu, G. Y.; Chen, Y. & Budny, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Alpha-driven magnetohydrodynamics (MHD) and MHD-induced alpha loss in the Tokamak Fusion Test Reactor

Description: Alpha-driven toroidal Alfven eigenmodes (TAEs) are observed as predicted by theory in the post neutral beam phase in high central q (safety factor) deuterium-tritium (D-T) plasmas in the Tokamak Fusion Test Reactor (TFTR). The mode location, poloidal structure and the importance of q profile for TAE instability are discussed. So far no alpha particle loss due to these modes was detected due to the small mode amplitude. However, alpha loss induced by kinetic ballooning modes (KBMs) was observed … more
Date: February 1, 1997
Creator: Chang, Z.; Nazikian, R. & Fu, G. Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Plasma simulation studies using multilevel physics models

Description: The question of how to proceed toward ever more realistic plasma simulation studies using ever increasing computing power is addressed. The answer presented here is the M3D (Multilevel 3D) project, which has developed a code package with a hierarchy of physics levels that resolve increasingly complete subsets of phase-spaces and are thus increasingly more realistic. The rationale for the multilevel physics models is given. Each physics level is described and examples of its application are give… more
Date: January 19, 2000
Creator: Park, W.; Belova, E. V. & Fu, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Energetic particle physics issues for ITER

Description: This paper summarizes our present understanding of the following energetic/alpha particle physics issues for the 21 MA, 20 TF coil ITER Interim Design configuration and operational scenarios: (a) toroidal field ripple effects on alpha particle confinement, (b) energetic particle interaction with low frequency MHD modes, (c) energetic particle excitation of toroidal Alfven eigenmodes, and (d) energetic particle transport due to MHD modes. TF ripple effects on alpha loss in ITER under a number of… more
Date: December 31, 1996
Creator: Cheng, C. Z.; Budny, R. & Fu, G. Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Stability of the toroidicity-induced Alfven eigenmodes in JT-60U ICRF experiments

Description: It is shown that the stability of toroidicity-induced Alfven eigenmodes (TIE) in JT-60U ICRF experiments is strongly dependent on mode location. This dependence results in sequential excitation of high-n TIE modes as the central safety factor, q, drops in time.
Date: April 1, 1996
Creator: Fu, G. Y.; Cheng, C. Z.; Kimura, H.; Ozeki, T. & Saigusa, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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3D simulation studies of tokamak plasmas using MHD and extended-MHD models

Description: The M3D (Multi-level 3D) tokamak simulation project aims at the simulation of tokamak plasmas using a multi-level tokamak code package. Several current applications using MHD and Extended-MHD models are presented; high-{beta} disruption studies in reversed shear plasmas using the MHD level MH3D code, {omega}{sub *i} stabilization and nonlinear island saturation of TAE mode using the hybrid particle/MHD level MH3D-K code, and unstructured mesh MH3D{sup ++} code studies. In particular, three inte… more
Date: December 31, 1996
Creator: Park, W.; Chang, Z.; Fredrickson, E. & Fu, G. Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Alpha Particle-Driven Toroidal Alfven Eigenmodes in Tokamak Fusion Test Reactor Deuterium-Tritium Plasmas: Theory and Experiments

Description: The toroidal Alfvén eigenmodes (TAE) in the Tokamak Fusion Test Reactor [K. Young, et al., Plasma Phys. Controlled Fusion 26, 11 (1984)]deuterium-tritium plasmas are analyzed using the NOVA-K code [C.Z. Cheng, Phys. Reports 211, 1 (1992)]. The theoretical results are compared with the experimental measurements in detail. In most cases, the theory agrees with the observations in terms of mode frequency, mode structure, and mode stability. However, one mode with toroidal mode number n = 2 is obse… more
Date: July 9, 1998
Creator: Budny, R.; Chang, Z.; Fu, G. Y. & Nazikian, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Global Hybrid Simulations of Energetic Particle-driven Modes in Toroidal Plasmas

Description: Global hybrid simulations of energetic particle-driven MHD modes have been carried out for tokamaks and spherical tokamaks using the hybrid code M3D. The numerical results for the National Spherical Tokamak Experiments (NSTX) show that Toroidal Alfven Eigenmodes are excited by beam ions with their frequencies consistent with the experimental observations. Nonlinear simulations indicate that the n=2 mode frequency chirps down as the mode moves out radially. For ITER, it is shown that the alpha-p… more
Date: December 14, 2004
Creator: Fu, G. Y.; Breslau, J.; Fredrickson, E.; Park, W. & Strauss, H. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Robustness and flexibility in compact quasiaxial stellarators: Global ideal MHD stability and energetic particle transport

Description: Concerns about the flexibility and robustness of a compact quasiaxial stellarator design are addressed by studying the effects of varied pressure and rotational transform profiles on expected performance. For thirty, related, fully three-dimensional configurations the global, ideal magnetohydrodynamic stability is evaluated as well as energetic particle transport. It is found that tokamak intuition is relevant to understanding the magnetohydrodynamic stability, with pressure gradient driving te… more
Date: January 27, 2000
Creator: Redi, M. H.; Diallo, A.; Cooper, W. A. & Fu, G. Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Acceleration of calcite kinetics by abalone nacre proteins

Description: The fascinating shapes and hierarchical designs of biomineralized structures have long been an inspiration to materials scientists because of the potential they suggest for biomolecular control over synthesis of crystalline materials. One prevailing view is that mineral-associated macromolecules are responsible for initiating and stabilizing non-equilibrium crystal polymorphs and morphologies through interactions between anionic moieties and cations in solution or at mineral surfaces. Indeed, n… more
Date: June 9, 2005
Creator: Fu, G.; Qiu, S. R.; Orme, C. A.; Morse, D. E. & De Yoreo, J. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Properties of High Beta, Quasi-Axisymmetric NCSX Stellarator Configurations

Description: Quasi-axisymmetry, external kinks and ballooning stability are studied with respect to the plasma shaping and the variation in the pressure and current profiles for NCSX. We show that while the kink stability may require a delicate boundary shaping, most quasi-axisymmetry may be achieved using a few low order modes that eliminate the large mirror fields arising partly from boundary shaping for the kink stability. In addition, we demonstrate that the kink and ballooning instability may be improv… more
Date: November 1, 1999
Creator: Boozer, A.; Reiman, A.; Monticello, D.; Fu, G. Y. & Ku, L. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Magnetohydodynamics stability of compact stellarators

Description: Recent stability results of external kink modes and vertical modes in compact stellarators are presented. The vertical mode is found to be stabilized by externally generated poloidal flux. A simple stability criterion is derived in the limit of large aspect ratio and constant current density. For a wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by Fi = (k2 {minus} k)=(k2 + 1), where k is the axisymmetric elongation and Fi is the fraction… more
Date: January 3, 2000
Creator: Fu, G. Y.; Ku, L. P.; Cooper, W. A. & Hirshman, S. H.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Properties of High Beta, Quasi-Axisymmetric NCSX Stellarator Configurations

Description: Quasi-axisymmetry, external kinks and ballooning stability are studied with respect to the plasma shaping and variation in the pressure and current profiles for NCSX. We show that while the kink stability may require a delicate boundary shaping, most quasi-axisymmetry may be achieved using a few low order modes that eliminate the large mirror fields arising partly from boundary shaping for the kink stability. In addition, we demonstrate that the kink and ballooning instability may be improved i… more
Date: September 28, 1999
Creator: Boozer, A.; Fu, G. Y.; Ku, L. P.; Monticello, D. & Reiman, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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