Author | Title | Year | Journal/Proceedings | DOI/URL | |
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Bass, M. & Waltz, R.E. | Gyrokinetic simulations of mesoscale energetic particle driven Alfvenic turbulent transport embedded in microturbulence [BibTeX] |
2010 | Phys. Plasmas Vol. November issue, pp. in press |
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BibTeX:
@article{MBass10a, author = {M. Bass and R. E. Waltz,}, title = {Gyrokinetic simulations of mesoscale energetic particle driven Alfvenic turbulent transport |
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Biancalani, A., Chen, L., Pegoraro, F. & Zonca, F. | Continuous Spectrum of Shear Alfvén Waves within Magnetic Islands | 2010 | Phys. Rev. Lett. Vol. 105(9), pp. 095002 |
DOI | |

Abstract: The radial structure of the shear Alfvén wave continuous spectrum is calculated inside the separatrix of a magnetic island. We find that, within a magnetic island, there is a continuous spectrum very similar to that of tokamak plasmas, where a generalized safety factor q can be defined and a wide frequency gap is formed, analogous to the ellipticity induced Alfvén eigenmode gap in tokamaks. This is due to the strong eccentricity of the island cross section. In this gap, a magnetic-island induced Alfvén eigenmode (MIAE) can exist as a bound state, essentially free of continuum damping, which can be resonantly excited by energetic particles and interact nonlinearly with the magnetic island. Because of the frequency dependence of the shear Alfvén wave continuum on the magnetic-island size, the possibility of utilizing MIAE frequency scalings as a novel magnetic-island diagnostic is also discussed. |
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BibTeX:
@article{PhysRevLett.105.095002, author = {Biancalani, Alessandro and Chen, Liu and Pegoraro, Francesco and Zonca, Fulvio}, title = {Continuous Spectrum of Shear Alfvén Waves within Magnetic Islands}, journal = {Phys. Rev. Lett.}, publisher = {American Physical Society}, year = {2010}, volume = {105}, number = {9}, pages = {095002}, doi = {http://dx.doi.org/10.1103/PhysRevLett.105.095002} } |
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Bierwage, A. & Chen, L. | AWECS: A linear gyrokinetic delta-f particle-in-cell simulation code for the study of Alfvénic instabilities in high-beta tokamak plasmas | 2008 | Commun. Comput. Phys. Vol. 4, pp. 457 |
URL | |

Abstract: A 1-D linear gyrokinetic code called AWECS is developed to study the kineticexcitation of Alfv ́ nic instabilities in a high-β tokamak plasma, with β being the ratio of thermal to magnetic pressure. It is designed to describe physics associated with a broad range of frequencies and wavelengths. For example, AWECS is capable of simu- lating kinetic ballooning modes, Alfv ́ nic ion-temperature-gradient-driven modes, as well as Alfv ́ n instabilities due to energetic particles. In addition, AWECS may be used to study drift-Alfv ́ n instabilities in the low-β regime. Here, the layout of the code and the numerical methods used are described. AWECS is benchmarked against other codes and a convergence study is carried out. |
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BibTeX:
@article{Bierwage08a, author = {A. Bierwage and L. Chen}, title = {AWECS: A linear gyrokinetic delta-f particle-in-cell simulation code for the study of Alfvénic instabilities in high-beta tokamak plasmas}, journal = {Commun. Comput. Phys.}, year = {2008}, volume = {4}, pages = {457}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Bierwage08a.pdf} } |
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Bierwage, A., Chen, L. & Zonca, F. | Pressure-gradient-induced Alfvén eigenmodes: I. Ideal MHD and finite ion Larmor radius effects | 2010 | Plasma Physics and Controlled Fusion Vol. 52(1), pp. 015004 |
URL | |

Abstract: In the second magnetohydrodynamic (MHD) ballooning stable domain of a high-beta tokamak plasma, the Schrödinger equation for ideal MHD shear Alfvén waves has discrete solutions corresponding to standing waves trapped between pressure-gradient-induced potential wells. Our goal is to understand how these so-called α-induced toroidal Alfvén eigenmodes (αTAE) are modified by the effects of finite Larmor radii (FLR) and kinetic compression of thermal ions in the limit of massless electrons. In this paper, we neglect kinetic compression in order to isolate and examine in detail the effect of FLR terms. After a review of the physics of ideal MHD αTAE, the effect of FLR on the Schrödinger potential, eigenfunctions and eigenvalues is described with the use of parameter scans. The results are used in a companion paper to identify instabilities driven by wave–particle resonances in the second stable domain. |
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BibTeX:
@article{0741-3335-52-1-015004, author = {A Bierwage and L Chen and F Zonca}, title = {Pressure-gradient-induced Alfvén eigenmodes: I. Ideal MHD and finite ion Larmor radius effects}, journal = {Plasma Physics and Controlled Fusion}, year = {2010}, volume = {52}, number = {1}, pages = {015004}, url = {http://stacks.iop.org/0741-3335/52/i=1/a=015004} } |
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Bierwage, A., Chen, L. & Zonca, F. | Pressure-gradient-induced Alfvén eigenmodes: II. Kinetic excitation with ion temperature gradient | 2010 | Plasma Physics and Controlled Fusion Vol. 52(1), pp. 015005 |
URL | |

Abstract: The kinetic excitation of ideal magnetohydrodynamic (MHD) discrete Alfvén eigenmodes in the second MHD ballooning stable domain is studied in the presence of a thermal ion temperature gradient (ITG), using linear gyrokinetic particle-in-cell simulations of a local flux tube in shifted-circle tokamak geometry. The instabilities are identified as α-induced toroidal Alfvén eigenmodes (αTAE); that is, bound states trapped between pressure-gradient-induced potential barriers of the Schrödinger equation for shear Alfvén waves. Using numerical tools, we examine in detail the effect of kinetic thermal ion compression on αTAEs; both non-resonant coupling to ion sound waves and wave–particle resonances. It is shown that the Alfvénic ITG instability thresholds (e.g., the critical temperature gradient) are determined by two resonant absorption mechanisms: Landau damping and continuum damping. The numerical results are interpreted on the basis of a theoretical framework previously derived from a variational formulation. The present analysis of properties and structures of Alfvénic fluctuations in the presence of steep pressure gradients applies for both positive or negative magnetic shear and can serve as an interpretative framework for experimental observations in (future) high-performance fusion plasmas of reactor relevance. |
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BibTeX:
@article{0741-3335-52-1-015005, author = {A Bierwage and L Chen and F Zonca}, title = {Pressure-gradient-induced Alfvén eigenmodes: II. Kinetic excitation with ion temperature gradient}, journal = {Plasma Physics and Controlled Fusion}, year = {2010}, volume = {52}, number = {1}, pages = {015005}, url = {http://stacks.iop.org/0741-3335/52/i=1/a=015005} } |
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Chavdarovski, I. & Zonca, F. | Effects of trapped particle dynamics on the structures of a low-frequency shear Alfvén continuous spectrum | 2009 | Plasma Physics and Controlled Fusion Vol. 51(11), pp. 115001 |
URL | |

Abstract: We analytically derive the structures of the low-frequency shear Alfvén continuous spectrum due to resonant wave–particle interactions with magnetically trapped thermal particles in tokamaks. Our theoretical description asymptotically recovers known results in the relevant limits at both high and low frequencies; furthermore, it is relevant for assessing the accurate kinetic structures that are due to shear Alfvén and acoustic wave spectra in toroidal geometry. Since there is a continuous transition between various shear Alfvén wave and MHD fluctuation branches in many situations of experimental interest, the results reported in this work are of practical relevance for their interpretation when used in the theoretical framework of the general 'fishbone-like' dispersion relation. |
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BibTeX:
@article{Chavdarovski09a, author = {Ilija Chavdarovski and Fulvio Zonca}, title = {Effects of trapped particle dynamics on the structures of a low-frequency shear Alfvén continuous spectrum}, journal = {Plasma Physics and Controlled Fusion}, year = {2009}, volume = {51}, number = {11}, pages = {115001}, url = {http://phoenix.ps.uci.edu/gsep/pubs/Zonca09a.pdf} } |
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Chen, K.R., Tsai, T.H. & Chen, L. | Localized cyclotron mode driven by fast $$ particles under a nonuniform magnetic field | 2010 | Phys. Rev. E Vol. 81(2), pp. 026404 |
DOI | |

Abstract: Resonance requires precise synchronization. Surprisingly, relativistic cyclotron instability can survive under a magnetic field with its nonuniformity larger than the requirement of synchronism. Localized eigenmode observed in a hybrid simulation is found to be consistent with that predicted by an analytical theory including both profile and eigenvalue. Half of the spatial area of the wave profile is located where the frequency mismatch is negative as against to the positive requirement generally believed. The consequence on the α dynamics is also demonstrated. |
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BibTeX:
@article{PhysRevE.81.026404, author = {Chen, K. R. and Tsai, T. H. and Chen, L.}, title = {Localized cyclotron mode driven by fast $$ particles under a nonuniform magnetic field}, journal = {Phys. Rev. E}, publisher = {American Physical Society}, year = {2010}, volume = {81}, number = {2}, pages = {026404}, doi = {http://dx.doi.org/10.1103/PhysRevE.81.026404} } |
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Chen, L. | Alfvén waves: a journey between space and fusion plasmas | 2008 | Plasma Physics and Controlled Fusion Vol. 50(12), pp. 124001 |
URL | |

Abstract: Alfvén waves discovered by Hannes Alfvén (1942 Nature 150 405) are fundamental electromagnetic oscillations in magnetized plasmas existing in the nature and laboratories. Alfvén waves play important roles in the heating, stability and transport of plasmas. The anisotropic nearly incompressible shear Alfvén wave is particularly interesting since, in realistic non-uniform plasmas, its wave spectra consist of both the regular discrete and the singular continuous components. In this Alfvén lecture, I will discuss these spectral properties and examine their significant linear and nonlinear physics implications. These discussions will be based on perspectives from my own research in both space and laboratory fusion plasmas, and will demonstrate the positive feedback and cross-fertilization between these two important sub-disciplines of plasma physics research. Some open issues of nonlinear Alfvén wave physics in burning fusion as well as magnetospheric space plasmas will also be explored. |
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BibTeX:
@article{Chen08a, author = {Liu Chen}, title = {Alfvén waves: a journey between space and fusion plasmas}, journal = {Plasma Physics and Controlled Fusion}, year = {2008}, volume = {50}, number = {12}, pages = {124001}, url = {http://phoenix.ps.uci.edu/GSEP/chen_alfven/Alfven-paper.pdf} } |
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Deng, W. & Lin, Z. | Properties of microturbulence in toroidal plasmas with reversed magnetic shear [BibTeX] |
2009 | Physics of Plasmas Vol. 16(10), pp. 102503 |
DOI URL | |

BibTeX:
@article{deng10a, author = {Wenjun Deng and Zhihong Lin}, title = {Properties of microturbulence in toroidal plasmas with reversed magnetic shear}, journal = {Physics of Plasmas}, publisher = {AIP}, year = {2009}, volume = {16}, number = {10}, pages = {102503}, url = {http://phoenix.ps.uci.edu/zlin/bib/dengwj09.pdf}, doi = {http://dx.doi.org/10.1063/1.3243918} } |
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Feng Liu, Z. Lin, J.Q.D.K.J.Z. | Gyrokinetic Simulation of Turbulence Driven Geodesic Acoustic Modes in Edge Plasmas of HL- 2A Tokamak [BibTeX] |
2010 | Phys. Plasmas Vol. October issue, pp. in press |
URL | |

BibTeX:
@article{liuf10, author = {Feng Liu, Z. Lin, J. Q. Dong, K. J. Zhao}, title = {Gyrokinetic Simulation of Turbulence Driven Geodesic Acoustic Modes in Edge Plasmas of HL- |
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Guo, Z., Crabtree, C. & Chen, L. | Theory of charged particle heating by low-frequency Alfv[e-acute]n waves [BibTeX] |
2008 | Physics of Plasmas Vol. 15(3), pp. 032311 |
DOI URL | |

BibTeX:
@article{guo08a, author = {Zehua Guo and Chris Crabtree and Liu Chen}, title = {Theory of charged particle heating by low-frequency Alfv[e-acute]n waves}, journal = {Physics of Plasmas}, publisher = {AIP}, year = {2008}, volume = {15}, number = {3}, pages = {032311}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Guo08.pdf}, doi = {http://dx.doi.org/10.1063/1.2899326} } |
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H.S. Zhang, Z. Lin, I.H.X.W.Y.X.W.L.Z. | Gyrokinetic particle simulation of beta-induced Alfven eigenmode [BibTeX] |
2010 | Phys. Plasmas Vol. October issue, pp. in press |
URL | |

BibTeX:
@article{zhanghs10b, author = {H. S. Zhang, Z. Lin, I. Holod, X. Wang, Y. Xiao, W. L. Zhang}, title = {Gyrokinetic particle simulation of beta-induced Alfven eigenmode}, journal = {Phys. Plasmas}, year = {2010}, volume = {October issue}, pages = {in press}, url = {http://phoenix.ps.uci.edu/zlin/bib/zhanghs10b.pdf} } |
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Heidbrink WW, Luo Y, M.C.Z.Y.B.K. | A new fast-ion D-alpha diagnostic for DIII-D | 2008 | Rev. Sci. Instrum. Vol. 79, pp. 10E520 |
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Abstract: The fast-ion D(alpha) (FIDA) technique is a charge-exchange recombination spectroscopy measurement that exploits the large Doppler shift of Balmer-alpha light from energetic hydrogenic atoms to infer the fast-ion density. Operational experience with the first dedicated FIDA diagnostic on DIII-D is guiding the design of the second-generation instrument. In the first instrument, dynamic changes in background light associated with plasma instabilities usually dominate measurement uncertainties. Accordingly, the design of the new instrument minimizes scattering of cold D(alpha) light while monitoring its level. The first instrument uses a vertical view to avoid bright interference from the injected-neutral beams. The sightline of the new instrument includes a toroidal component but only measures blueshifted fast-ion light that is Doppler shifted away from the redshifted light of the injected neutrals. The new views are more sensitive to fast ions that circulate in the direction of the plasma current and less sensitive to the trapped-ion and countercirculating populations. Details of the design criteria and solutions are presented. |
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BibTeX:
@article{Heidbrink08c, author = {Heidbrink WW, Luo Y, Muscatello CM, Zhu Y, Burrell KH.}, title = {A new fast-ion D-alpha diagnostic for DIII-D}, journal = {Rev. Sci. Instrum.}, year = {2008}, volume = {79}, pages = {10E520} } |
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Heidbrink, W., Zeeland, M.V., Austin, M., Burrell, K., Gorelenkov, N., Kramer, G., Luo, Y., Makowski, M., McKee, G., Muscatello, C., Nazikian, R., Ruskov, E., Solomon, W., White, R. & Zhu, Y. | Central flattening of the fast-ion profile in reversed-shear DIII-D discharges | 2008 | Nuclear Fusion Vol. 48(8), pp. 084001 |
URL | |

Abstract: Neutral beam injection into a plasma with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The application of fast-ion D α (FIDA) spectroscopy shows that the central fast-ion profile is flattened in the inner half of the discharge. Neutron and equilibrium measurements corroborate the FIDA data. The temporal evolution of the current profile is also strongly modified. Studies in similar discharges show that flattening of the profile correlates with the mode amplitude and that both types of Alfvén modes correlate with fast-ion transport. Calculations by the ORBIT code do not explain the observed fast-ion transport for the measured mode amplitudes, however. Possible explanations for the discrepancy are considered. |
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BibTeX:
@article{Heidbrink08b, author = {W.W. Heidbrink and M.A. Van Zeeland and M.E. Austin and K.H. Burrell and N.N. Gorelenkov and G.J. Kramer and Y. Luo and M.A. Makowski and G.R. McKee and C. Muscatello and R. Nazikian and E. Ruskov and W.M. Solomon and R.B. White and Y. Zhu}, title = {Central flattening of the fast-ion profile in reversed-shear DIII-D discharges}, journal = {Nuclear Fusion}, year = {2008}, volume = {48}, number = {8}, pages = {084001}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Heidbrink08b.pdf} } |
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Heidbrink, W.W. | Basic physics of Alfv[e-acute]n instabilities driven by energetic particles in toroidally confined plasmas [BibTeX] |
2008 | Physics of Plasmas Vol. 15(5), pp. 055501 |
DOI URL | |

BibTeX:
@article{heidbrink08a, author = {W. W. Heidbrink}, title = {Basic physics of Alfv[e-acute]n instabilities driven by energetic particles in toroidally confined plasmas}, journal = {Physics of Plasmas}, publisher = {AIP}, year = {2008}, volume = {15}, number = {5}, pages = {055501}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Heidbrink08a.pdf}, doi = {http://dx.doi.org/10.1063/1.2838239} } |
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Isobe, M., Toi, K., Osakabe, M., Nagaoka, K., Shimizu, A., Spong, D.A., Okamura, S., CHS & Group, L.E. | Effects of Energetic-Ion-Driven MHD Instabilities on Energetic-Ion-Transport in Compact Helical System and Large Helical Device [BibTeX] |
2010 | Contrib. Plasma Phys. Vol. 50, pp. 540 |
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BibTeX:
@article{MIsobe10a, author = {Isobe, M. and Toi, K and Osakabe, M. and Nagaoka, K. and Shimizu, A. and Spong, D. A. and Okamura, S. and CHS and LHD Experiment Group}, title = {Effects of Energetic-Ion-Driven MHD Instabilities on Energetic-Ion-Transport in Compact Helical |
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Lin, Z., Xiao, Y., Holod, I., Zhang, W., Deng, W., Klasky, S., Lofstead, J., Kamath, C. & Wichmann, N. | Advanced simulation of electron heat transport in fusion plasmas | 2009 | Journal of Physics: Conference Series Vol. 180(1), pp. 012059 |
URL | |

Abstract: Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E X B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual quasilinear theory for the CTEM electron transport. This is in contrast to the good agreement between the quasilinear transport theory and simulation results of the electron heat transport in electron temperature gradient (ETG) turbulence, which is regulated by a wave-particle decorrelation. Therefore, the transport in the CTEM turbulence is a fluid-like eddy mixing process even though the linear CTEM instability is driven by a kinetic resonance. In contrast, a kinetic process dominates the transport in the ETG turbulence, which is characterized by macroscopic streamers. |
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BibTeX:
@article{Lin09a, author = {Z Lin and Y Xiao and I Holod and W Zhang and W Deng and S Klasky and J Lofstead and C Kamath and N Wichmann}, title = {Advanced simulation of electron heat transport in fusion plasmas}, journal = {Journal of Physics: Conference Series}, year = {2009}, volume = {180}, number = {1}, pages = {012059}, url = {http://phoenix.ps.uci.edu/zlin/bib/SciDAC09p.pdf} } |
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Lore, J., Guttenfelder, W., Briesemeister, A., Anderson, D.T., Anderson, F.S.B., Deng, C.B., Likin, K.M., Spong, D.A., Talmadge, J.N. & Zhai, K. | Internal electron transport barrier due to neoclassical ambipolarity in the Helically Symmetric Experiment | 2010 | Physics of Plasmas Vol. 17(5), pp. 056101 |
DOI URL | |

Abstract: Electron cyclotron heated plasmas in the Helically Symmetric Experiment (HSX) feature strongly peaked electron temperature profiles; central temperatures are 2.5 keV with 100 kW injected power. These measurements, coupled with neoclassical predictions of large “electron root” radial electric fields with strong radial shear, are evidence of a neoclassically driven thermal transport barrier. Neoclassical transport quantities are calculated using the PENTA code [ D. A. Spong, Phys. Plasmas 12, 056114 (2005) ], in which momentum is conserved and parallel flow is included. Unlike a conventional stellarator, which exhibits strong flow damping in all directions on a flux surface, quasisymmetric stellarators are free to rotate in the direction of symmetry, and the effect of momentum conservation in neoclassical calculations may therefore be significant. Momentum conservation is shown to modify the neoclassical ion flux and ambipolar ion root radial electric fields in the quasisymmetric configuration. The effect is much smaller in a HSX configuration where the symmetry is spoiled. In addition to neoclassical transport, a model of trapped electron mode turbulence is used to calculate the turbulent-driven electron thermal diffusivity. Turbulent transport quenching due to the neoclassically predicted radial electric field profile is needed in predictive transport simulations to reproduce the peaking of the measured electron temperature profile [ Guttenfelder et al., Phys. Rev. Lett. 101, 215002 (2008) ] |
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BibTeX:
@article{lore:056101, author = {J. Lore and W. Guttenfelder and A. Briesemeister and D. T. Anderson and F. S. B. Anderson and C. B. Deng and K. M. Likin and D. A. Spong and J. N. Talmadge and K. Zhai}, title = {Internal electron transport barrier due to neoclassical ambipolarity in the Helically Symmetric Experiment}, journal = {Physics of Plasmas}, publisher = {AIP}, year = {2010}, volume = {17}, number = {5}, pages = {056101}, url = {http://link.aip.org/link/?PHP/17/056101/1}, doi = {http://dx.doi.org/10.1063/1.3300465} } |
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Nishimura, Y. | Excitation of low-n toroidicity induced Alfv[e-acute]n eigenmodes by energetic particles in global gyrokinetic tokamak plasmas [BibTeX] |
2009 | Physics of Plasmas Vol. 16(3), pp. 030702 |
DOI URL | |

BibTeX:
@article{nishimura09b, author = {Y. Nishimura}, title = {Excitation of low-n toroidicity induced Alfv[e-acute]n eigenmodes by energetic particles in global gyrokinetic tokamak plasmas}, journal = {Physics of Plasmas}, publisher = {AIP}, year = {2009}, volume = {16}, number = {3}, pages = {030702}, url = {http://phoenix.ps.uci.edu/gtc/pubs/Nishimura-PoP09.pdf}, doi = {http://dx.doi.org/10.1063/1.3088028} } |
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Nishimura, Y., Lin, Z. & Chen, L. | Full Torus Electromagnetic Gyrokinetic Particle Simulations with Kinetic Electrons | 2009 | Commun. Comput. Phys. Vol. 5, pp. 183 |
URL | |

Abstract: The full torus electromagnetic gyrokinetic particle simulations using the hy-brid model with kinetic electrons in the presence of magnetic shear is presented. The fluid-kinetic electron hybrid model employed in this paper improves numerical prop- erties by removing the tearing mode, meanwhile, preserves both linear and nonlinear wave-particle resonances of electrons with Alfven wave and ion acoustic wave. |
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BibTeX:
@article{Nishimura09, author = {Y. Nishimura and Z. Lin and L. Chen}, title = {Full Torus Electromagnetic Gyrokinetic Particle Simulations with Kinetic Electrons}, journal = {Commun. Comput. Phys.}, year = {2009}, volume = {5}, pages = {183}, url = {http://phoenix.ps.uci.edu/zlin/bib/nishimura09.pdf} } |
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Ogawa, K., Isobe, M., Toi, K., Watanabe, F., Spong, D., Shimizu, A., Osakabe, M., Ohdachi, S., Sakakibara, S. & Group, L.E. | Observation of energetic-ion losses induced by various MHD instabilities in the Large Helical Device (LHD) | 2010 | Nuclear Fusion Vol. 50(8), pp. 084005 |
URL | |

Abstract: Energetic-ion losses induced by toroidicity-induced Alfvén eigenmodes (TAEs) and resistive interchange modes (RICs) were observed in neutral-beam heated plasmas of the Large Helical Device (LHD) at a relatively low toroidal magnetic field level (≤0.75 T). The energy and pitch angle of the lost ions are detected using a scintillator-based lost-fast ion probe. Each instability increases the lost ions having a certain energy/pitch angle. TAE bursts preferentially induce energetic beam ions in co-passing orbits having energy from the injection energy E = 190 keV down to 130 keV, while RICs expel energetic ions of E = 190 keV down to ~130 keV in passing–toroidally trapped boundary orbits. Loss fluxes induced by these instabilities increase with different dependences on the magnetic fluctuation amplitude: nonlinear and linear dependences for TAEs and RICs, respectively. |
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BibTeX:
@article{0029-5515-50-8-084005, author = {K. Ogawa and M. Isobe and K. Toi and F. Watanabe and D.A. Spong and A. Shimizu and M. Osakabe and S. Ohdachi and S. Sakakibara and LHD Experiment Group}, title = {Observation of energetic-ion losses induced by various MHD instabilities in the Large Helical Device (LHD)}, journal = {Nuclear Fusion}, year = {2010}, volume = {50}, number = {8}, pages = {084005}, url = {http://stacks.iop.org/0029-5515/50/i=8/a=084005} } |
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Qiu, Z., Chen, L. & Zonca, F. | Collisionless damping of short wavelength geodesic acoustic modes | 2009 | Plasma Physics and Controlled Fusion Vol. 51(1), pp. 012001 |
URL | |

Abstract: Collisionless damping of geodesic acoustic mode (GAM) excited in the large safety factor ( q ) region of a tokamak plasma is investigated taking into account the effects of finite ion Larmor radius and guiding-center drift orbit width as well as parallel electric field contributions. A corresponding analytical expression for the damping rate including higher-order harmonics of ion transit resonances is systematically derived and agrees well with numerical results in its validity regime. |
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BibTeX:
@article{Qiu09a, author = {Zhiyong Qiu and Liu Chen and Fulvio Zonca}, title = {Collisionless damping of short wavelength geodesic acoustic modes}, journal = {Plasma Physics and Controlled Fusion}, year = {2009}, volume = {51}, number = {1}, pages = {012001}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Qiu09a.pdf} } |
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Qiu, Z., Zonca, F. & Chen, L. | Nonlocal theory of energetic-particle-induced geodesic acoustic mode | 2010 | Plasma Physics and Controlled Fusion Vol. 52(9), pp. 095003 |
URL | |

Abstract: Excitation of energetic-particle (EP)-induced geodesic acoustic modes (EGAMs) by velocity space anisotropy is investigated taking into account the coupling to the GAM continuous spectrum. The response of EPs is studied nonperturbatively and both local and nonlocal dispersion relations of EGAM are derived assuming a single pitch angle slowing-down energetic ion equilibrium distribution function. For a sharply localized EP source, it is shown that the mode is self-trapped where the EP drive is strongest, with an exponentially small damping due to the tunneling coupling to the GAM continuous spectrum. |
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BibTeX:
@article{0741-3335-52-9-095003, author = {Zhiyong Qiu and Fulvio Zonca and Liu Chen}, title = {Nonlocal theory of energetic-particle-induced geodesic acoustic mode}, journal = {Plasma Physics and Controlled Fusion}, year = {2010}, volume = {52}, number = {9}, pages = {095003}, url = {http://phoenix.ps.uci.edu/gsep/workshop/Qiu.pdf} } |
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Spong, D.A., Breizman, B.N., Brower, D.L., D'Azevedo, E., Deng, C.B., Konies, A., Todo, Y. & Toi, K. | Energetic-Particle-Driven Instabilities in General Toroidal Configurations [BibTeX] |
2010 | Contributions to Plasma Physics Vol. 50, pp. 708-712 |
DOI URL | |

BibTeX:
@article{2010CoPP...50..708S, author = {Spong, D.~A. and Breizman, B.~N. and Brower, D.~L. and D'Azevedo, E. and Deng, C.~B. and Konies, A. and Todo, Y. and Toi, K.}, title = {Energetic-Particle-Driven Instabilities in General Toroidal Configurations}, journal = {Contributions to Plasma Physics}, year = {2010}, volume = {50}, pages = {708-712}, url = {http://adsabs.harvard.edu/abs/2010CoPP...50..708S}, doi = {http://dx.doi.org/10.1002/ctpp.200900066} } |
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Spong, D.A., D'Azevedo, E. & Todo, Y. | Clustered frequency analysis of shear Alfvén modes in stellarators [BibTeX] |
2010 | Physics of Plasmas Vol. 17(2), pp. 022106-+ |
DOI URL | |

BibTeX:
@article{2010PhPl...17b2106S, author = {Spong, D.~A. and D'Azevedo, E. and Todo, Y.}, title = {Clustered frequency analysis of shear Alfvén modes in stellarators}, journal = {Physics of Plasmas}, year = {2010}, volume = {17}, number = {2}, pages = {022106-+}, url = {http://adsabs.harvard.edu/abs/2010PhPl...17b2106S}, doi = {http://dx.doi.org/10.1063/1.3313818} } |
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Todo, Y., Murakami, S., Yamamoto, T., Fukuyama, A., Spong, D.A., Yamamoto, S. & M. Osakabe, N.N. | Numerical Analyses of Energetic Particles in LHD [BibTeX] |
2010 | Fusion Science and Technology Vol. 58, pp. 277 |
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BibTeX:
@article{YTodo10a, author = {Y. Todo and S. Murakami and T. Yamamoto and A. Fukuyama and D. A. Spong and S. Yamamoto and M. Osakabe, N. Nakajima}, title = {Numerical Analyses of Energetic Particles in LHD}, journal = {Fusion Science and Technology}, year = {2010}, volume = {58}, pages = {277} } |
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Toi, K., Isobe, M., Osakabe, M., Ogawa, K., Spong, D. & Todo, Y. | Overview of Studies on Energetic-Ion-Driven MHD Instabilities in Stellarator/Helical Plasmas and Comparison with Tokamaks [BibTeX] |
2010 | Contrib. Plasma Phys. Vol. 50, pp. 493 |
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BibTeX:
@article{KToi10b, author = {K. Toi and M. Isobe and M. Osakabe and K. Ogawa and D. Spong and Y. Todo}, title = {Overview of Studies on Energetic-Ion-Driven MHD Instabilities in Stellarator/Helical Plasmas |
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Toi, K., M., M.I., Osakabe, Watanabe, F., Ogawa, K., Yamamoto, S., Nakajima, N., Spong, D.A., Ida, K. & T. Ido, T. Ito, S.M.K.N.K.N.M.N.S.O.S.S.A.S.K.T.Y.T.T.T.A.W.L.E.G. | MHD Modes Destabilized by Energetic Ions on LHD [BibTeX] |
2010 | Fusion Science and Technology Vol. 58, pp. 186 |
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BibTeX:
@article{KToi10a, author = {K. Toi and M. Isobe M. and Osakabe and F. Watanabe and K. Ogawa and S. Yamamoto and N. Nakajima and D. A. Spong and K. Ida and T. Ido, T. Ito, S. Morita, K. Nagaoka, K. Narihara, M. Nishiura, S. Ohdachi, S. Sakakibara, A. Shimizu, K. Tanaka, Y. Todo, T. Tokuzawa, A. Weller, LHD Experiment Group}, title = {MHD Modes Destabilized by Energetic Ions on LHD}, journal = {Fusion Science and Technology}, year = {2010}, volume = {58}, pages = {186} } |
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Toi, K., Watanabe, F., Tokuzawa, T., Ida, K., Morita, S., Ido, T., Shimizu, A., Isobe, M., Ogawa, K., Spong, D.A., Todo, Y., Watari, T., Ohdachi, S., Sakakibara, S., Yamamoto, S., Inagaki, S., Narihara, K., Osakabe, M., Nagaoka, K., Narushima, Y., Watanabe, K.Y., Funaba, H., Goto, M., Ikeda, K., Ito, T., Kaneko, O., Kubo, S., Murakami, S., Minami, T., Miyazawa, J., Nagayama, Y., Nishiura, M., Oka, Y., Sakamoto, R., Shimozuma, T., Takeiri, Y., Tanaka, K., Tsumori, K., Yamada, I., Yoshinuma, M., Kawahata, K. & Komori, A. | Observation of Reversed-Shear Alfvén Eigenmodes Excited by Energetic Ions in a Helical Plasma | 2010 | Phys. Rev. Lett. Vol. 105(14), pp. 145003 |
DOI | |

Abstract: Reversed-shear Alfvén eigenmodes were observed for the first timein a helical plasma having negative q0′′ (the curvature of the safety factor q at the zero shear layer). The frequency is swept downward and upward sequentially via the time variation in the maximum of q. The eigenmodes calculated by ideal MHD theory are consistent with the experimental data. The frequency sweeping is mainly determined by the effects of energetic ions and the bulk pressure gradient. Coupling of reversed-shear Alfvén eigenmodes with energetic ion driven geodesic acoustic modes generates a multitude of frequency-sweeping modes. |
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BibTeX:
@article{PhysRevLett.105.145003, author = {Toi, K. and Watanabe, F. and Tokuzawa, T. and Ida, K. and Morita, S. and Ido, T. and Shimizu, A. and Isobe, M. and Ogawa, K. and Spong, D. A. and Todo, Y. and Watari, T. and Ohdachi, S. and Sakakibara, S. and Yamamoto, S. and Inagaki, S. and Narihara, K. and Osakabe, M. and Nagaoka, K. and Narushima, Y. and Watanabe, K. Y. and Funaba, H. and Goto, M. and Ikeda, K. and Ito, T. and Kaneko, O. and Kubo, S. and Murakami, S. and Minami, T. and Miyazawa, J. and Nagayama, Y. and Nishiura, M. and Oka, Y. and Sakamoto, R. and Shimozuma, T. and Takeiri, Y. and Tanaka, K. and Tsumori, K. and Yamada, I. and Yoshinuma, M. and Kawahata, K. and Komori, A.}, title = {Observation of Reversed-Shear Alfvén Eigenmodes Excited by Energetic Ions in a Helical Plasma}, journal = {Phys. Rev. Lett.}, publisher = {American Physical Society}, year = {2010}, volume = {105}, number = {14}, pages = {145003}, doi = {http://dx.doi.org/10.1103/PhysRevLett.105.145003} } |
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Tsai, T.H., Chen, K.R. & Chen, L. | Relativistic ion cyclotron instability driven by energetic alpha particles in plasma under magnetic field with sinusoidal nonuniformities | 2010 | Plasma Physics and Controlled Fusion Vol. 52(1), pp. 015006 |
URL | |

Abstract: Localized electrostatic wave modes due to relativistic ion cyclotron instabilities are observed in a hybrid particle-in-cell simulation under a magnetic field with sinusoidal nonuniformity. In order to investigate the physical mechanism of the simulation results, an analytical theory, adopting a parabolic approximation around a magnetic field minimum, has been developed based on an absolute instability condition along with systematic expansion procedures. The spatial structure, growth rate and frequency of the localized wave modes predicted by the theory are found to agree well with those of simulation. In this work, we demonstrate that the instabilities can survive even when the magnetic variation is much larger than the Lorentz factor minus one. Furthermore, both the simulation and the theory show that the wave mode can exist where its frequency is smaller than the local harmonic cyclotron frequency, violating the well-known requirement for driving relativistic cyclotron instabilities. |
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BibTeX:
@article{0741-3335-52-1-015006, author = {T H Tsai and K R Chen and L Chen}, title = {Relativistic ion cyclotron instability driven by energetic alpha particles in plasma under magnetic field with sinusoidal nonuniformities}, journal = {Plasma Physics and Controlled Fusion}, year = {2010}, volume = {52}, number = {1}, pages = {015006}, url = {http://stacks.iop.org/0741-3335/52/i=1/a=015006} } |
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Vlad, G., Briguglio, S., Fogaccia, G., Zonca, F., Troia, C.D., Heidbrink, W., Zeeland, M.V., Bierwage, A. & Wang, X. | Particle simulation of energetic particle driven Alfvén modes in NBI heated DIII-D experiments | 2009 | Nuclear Fusion Vol. 49(7), pp. 075024 |
URL | |

Abstract: The mutual nonlinear interactions of shear Alfvén modes and alpha particles can enhance their transport in burning plasmas. Theoretical and numerical works have shown that rapid transport of energetic ions can take place because of fast growing Alfvén modes (e.g. energetic particle driven modes, EPMs). This kind of transport has been observed in experiments as well as in numerical simulations. Hybrid MHD-gyrokinetic codes can investigate linear and nonlinear dynamics of energetic particle (EP) driven modes, retaining the mutual interaction between waves and EPs self-consistently. Self-consistent nonlinear wave–particle interactions (both in configuration and velocity space) are crucial for a correct description of the mode dynamics in the case of strongly driven modes; thus, a non-perturbative approach is mandatory. The knowledge of the threshold characterizing the transition from weakly to strongly driven regimes is of primary importance for burning plasma operations (e.g. for ITER), in order to avoid EPM enhanced EP transport regimes. The hybrid MHD-gyrokinetic code (HMGC) has been applied to the interpretation of phenomena observed in present experiments with neutral beam (NB) heating. In reversed-shear beam-heated DIII-D discharges, a large discrepancy between the expected and measured EP radial density profiles has been observed in the presence of large Alfvénic activity. HMGC simulations with EP radial profiles expected from classical NB deposition as input give rise to strong EPM activity, resulting in relaxed EP radial profiles at saturation level close to experimental measurements. The frequency spectra obtained from several simulations with different toroidal mode numbers, as calculated during the saturated phase when the strong EPMs transform in weak reversed-shear Alfvén modes, are quite close to experimental observations both in absolute frequency and in radial localization. In this work, we discuss in particular the effects of nonlinear coupling between different toroidal mode numbers. |
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BibTeX:
@article{Vlad09a, author = {G. Vlad and S. Briguglio and G. Fogaccia and F. Zonca and C. Di Troia and W.W. Heidbrink and M.A. Van Zeeland and A. Bierwage and X. Wang}, title = {Particle simulation of energetic particle driven Alfvén modes in NBI heated DIII-D experiments}, journal = {Nuclear Fusion}, year = {2009}, volume = {49}, number = {7}, pages = {075024}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Vlad09a.pdf} } |
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Wang, X., Zonca, F. & Chen, L. | Theory and simulation of discrete kinetic beta induced Alfvén eigenmode in tokamak plasmas | 2010 | Plasma Physics and Controlled Fusion Vol. 52(11), pp. 115005 |
URL | |

Abstract: It is shown, both analytically and by numerical simulations, that, in the presence of thermal ion kinetic effects, the beta induced Alfvén eigenmode (BAE)–shear Alfvén wave continuous spectrum can be discretized into radially trapped eigenstates known as kinetic BAE (KBAE). While thermal ion compressibility gives rise to finite BAE accumulation point frequency, the discretization occurs via the finite Larmor radius and finite orbit width effects. Simulations and analytical theories agree both qualitatively and quantitatively. Simulations also demonstrate that KBAE can be readily excited by the finite radial gradients of energetic particles. |
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BibTeX:
@article{0741-3335-52-11-115005, author = {X Wang and F Zonca and L Chen}, title = {Theory and simulation of discrete kinetic beta induced Alfvén eigenmode in tokamak plasmas}, journal = {Plasma Physics and Controlled Fusion}, year = {2010}, volume = {52}, number = {11}, pages = {115005}, url = {http://stacks.iop.org/0741-3335/52/i=11/a=115005} } |
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Wenjun Deng, Zhihong Lin, I.H. b.X.W.Y.X. & Zhang., W. | Gyrokinetic particle simulations of reversed shear Alfven eigenmode excited by antenna and fast ions [BibTeX] |
2010 | Phys. Plasmas Vol. October issue, pp. in press |
URL | |

BibTeX:
@article{dengwj10, author = {Wenjun Deng, Zhihong Lin, Ihor Holod, begin_of_the_skype_highlightingend_of_the_skype_highlighting, Xin Wang, Yong Xiao, and |
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Wang, X., Zonca, F. & Chen, L. | Theory and simulation of discrete kinetic beta induced Alfven eigenmode in tokamak plasmas, [BibTeX] |
2010 | Plasma Physics and Controlled Fusion Vol. 52, pp. 115005 |
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BibTeX:
@article{XWang10a, author = {X. Wang, and F. Zonca, and L. Chen,}, title = {Theory and simulation of discrete kinetic beta induced Alfven eigenmode in tokamak plasmas,}, journal = {Plasma Physics and Controlled Fusion}, year = {2010}, volume = {52}, pages = {115005} } |
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Xiao, Y., Holod, I., Zhang, W., Klasky, S. & Lin, Z. | Fluctuation characteristics and transport properties of collisionless trapped electron mode turbulence [BibTeX] |
2010 | Physics of Plasmas Vol. 17(2), pp. 022302 |
DOI URL | |

BibTeX:
@article{xiao10a, author = {Yong Xiao and Ihor Holod and Wenlu Zhang and Scott Klasky and Zhihong Lin}, title = {Fluctuation characteristics and transport properties of collisionless trapped electron mode turbulence}, journal = {Physics of Plasmas}, publisher = {AIP}, year = {2010}, volume = {17}, number = {2}, pages = {022302}, url = {http://phoenix.ps.uci.edu/zlin/bib/xiaoy10a.pdf}, doi = {http://dx.doi.org/10.1063/1.3302504} } |
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Xiao, Y. & Lin, Z. | Turbulent Transport of Trapped-Electron Modes in Collisionless Plasmas [BibTeX] |
2009 | Phys. Rev. Lett. Vol. 103(8), pp. 085004 |
DOI URL | |

BibTeX:
@article{Xiao09a, author = {Xiao, Yong and Lin, Zhihong}, title = {Turbulent Transport of Trapped-Electron Modes in Collisionless Plasmas}, journal = {Phys. Rev. Lett.}, publisher = {American Physical Society}, year = {2009}, volume = {103}, number = {8}, pages = {085004}, url = {http://phoenix.ps.uci.edu/zlin/bib/xiaoy09.pdf}, doi = {http://dx.doi.org/10.1103/PhysRevLett.103.085004} } |
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Zeeland, M.A.V., Heidbrink, W.W., Nazikian, R., Solomon, W.M., Austin, M.E., Berk, H.L., Gorelenkov, N.N., Holcomb, C.T., Hyatt, A.W., Kramer, G.J., Lohr, J., Makowski, M.A., McKee, G.R., Petty, C.C., Sharapov, S.E. & Rhodes, T.L. | Reversed shear Alfvén eigenmode stabilization by localized electron cyclotron heating | 2008 | Plasma Physics and Controlled Fusion Vol. 50(3), pp. 035009 |
URL | |

Abstract: Reversed shear Alfvén eigenmode (RSAE) activity in DIII-D is stabilized by electron cyclotron heating (ECH) applied near the minimum of the magnetic safety factor ( q min ) in neutral beam heated discharges with reversed-magnetic shear. The degree of RSAE stabilization, fast ion density and the volume averaged neutron production ( S n ) are highly dependent on ECH deposition location relative to q min . While discharges with ECH stabilization of RSAEs have higher S n and more peaked fast ion profiles than discharges with significant RSAE activity, neutron production remains strongly reduced (up to 60% relative to TRANSP predictions assuming classical fast ion transport) even when RSAEs are stabilized. |
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BibTeX:
@article{Zeeland08a, author = {M A Van Zeeland and W W Heidbrink and R Nazikian and W M Solomon and M E Austin and H L Berk and N N Gorelenkov and C T Holcomb and A W Hyatt and G J Kramer and J Lohr and M A Makowski and G R McKee and C C Petty and S E Sharapov and T L Rhodes}, title = {Reversed shear Alfvén eigenmode stabilization by localized electron cyclotron heating}, journal = {Plasma Physics and Controlled Fusion}, year = {2008}, volume = {50}, number = {3}, pages = {035009}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Zeeland08a} } |
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Zeeland, M.A.V., Heidbrink, W.W. & Yu, J.H. | Fast ion D α imaging in the DIII-D tokamak | 2009 | Plasma Physics and Controlled Fusion Vol. 51(5), pp. 055001 |
URL | |

Abstract: Doppler shifted fast ion D α light (FIDA) emitted by neutralized energetic ions is imaged in the DIII-D tokamak using a fast framing camera in conjunction with a narrowband interference filter. Both the 2D spatial structure and temporal evolution of the FIDA emission are in agreement with Monte Carlo simulations assuming classical energetic ion slowing down. This technique can be used to obtain 2D energetic ion profile information in fusion plasmas. |
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BibTeX:
@article{Zeeland09b, author = {M A Van Zeeland and W W Heidbrink and J H Yu}, title = {Fast ion D α imaging in the DIII-D tokamak}, journal = {Plasma Physics and Controlled Fusion}, year = {2009}, volume = {51}, number = {5}, pages = {055001}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Zeeland09b.pdf} } |
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Zeeland, M.V., Heidbrink, W., Nazikian, R., Austin, M., Cheng, C., Chu, M., Gorelenkov, N., Holcomb, C., Hyatt, A., Kramer, G., Lohr, J., McKee, G., Petty, C., Prater, R., Solomon, W. & Spong, D. | Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D | 2009 | Nuclear Fusion Vol. 49(6), pp. 065003 |
URL | |

Abstract: Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfvénic activity including toroidicity and ellipticity induced Alfvén eigenmodes (TAE/EAE, respectively) and reversed shear Alfvén eigenmodes (RSAE) as well as their spatial coupling. These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and strong drive due to multiple higher order resonances. It is found that ideal MHD modelling of eigenmode spectral evolution, coupling and structure are in excellent agreement with experimental measurements. It is also found that higher radial envelope harmonic RSAEs are clearly observed and agree with modelling. Some discrepancies with modelling such as that due to up/down eigenmode asymmetries are also pointed out. Concomitant with the Alfvénic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfvén eigenmode amplitude. Interestingly, localized electron cyclotron heating (ECH) near the mode location stabilizes RSAE activity and results in significantly improved fast ion confinement relative to discharges with ECH deposition on axis. In these discharges, RSAE activity is suppressed when ECH is deposited near the radius of the shear reversal point and enhanced with deposition near the axis. The sensitivity of this effect to deposition power and current drive phasing as well as ECH modulation are presented. |
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BibTeX:
@article{Zeeland09a, author = {M.A. Van Zeeland and W.W. Heidbrink and R. Nazikian and M.E. Austin and C.Z. Cheng and M.S. Chu and N.N. Gorelenkov and C.T. Holcomb and A.W. Hyatt and G.J. Kramer and J. Lohr and G.R. McKee and C.C. Petty and R. Prater and W.M. Solomon and D.A. Spong}, title = {Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D}, journal = {Nuclear Fusion}, year = {2009}, volume = {49}, number = {6}, pages = {065003}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Zeeland09a.pdf} } |
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Zeeland, M.V., Yu, J., Heidbrink, W., Brooks, N., Burrell, K., Chu, M., Hyatt, A., Muscatello, C., Nazikian, R., Pablant, N., Pace, D., Solomon, W. & Wade, M. | Imaging key aspects of fast ion physics in the DIII-D tokamak | 2010 | Nuclear Fusion Vol. 50(8), pp. 084002 |
URL | |

Abstract: Visible imaging has been used to provide the 2D spatial structure and temporal evolution of the profile of high-energy neutrals introduced by neutral beam injection, the fast ion profile and a variety of plasma instabilities in DIII-D plasmas; the combination of these techniques form a comprehensive fast ion physics diagnostic suite. The injected neutral profile is imaged in Doppler shifted D α light induced by collisional excitation. Fast ion profile information was obtained through imaging of Doppler shifted fast ion D α light (FIDA) emitted by re-neutralized energetic ions. Imaging of FIDA emission during sawtooth events shows a large central depletion following sawtooth crashes—indicative of a broad redistribution of fast ions. Two examples of instability structure measurements are given. Measurements of the detailed 2D poloidal structure of rotating tearing modes were obtained using spectrally filtered fast imaging of broadband visible bremsstrahlung emission, a method which is capable of imaging with high resolution the structure of coherent oscillations in the core of current and next-step fusion plasma experiments and can be applied to virtually any mode with a finite perturbed bremsstrahlung emissivity and frequency in the laboratory frame. Measurements are also presented of the n = 0 energetic particle geodesic acoustic mode which were made by observing fluctuations in active emission. |
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BibTeX:
@article{0029-5515-50-8-084002, author = {M.A. Van Zeeland and J.H. Yu and W.W. Heidbrink and N.H. Brooks and K.H. Burrell and M.S. Chu and A.W. Hyatt and C. Muscatello and R. Nazikian and N.A. Pablant and D.C. Pace and W.M. Solomon and M.R. Wade}, title = {Imaging key aspects of fast ion physics in the DIII-D tokamak}, journal = {Nuclear Fusion}, year = {2010}, volume = {50}, number = {8}, pages = {084002}, url = {http://stacks.iop.org/0029-5515/50/i=8/a=084002} } |
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Zhang, H.S. & Lin, Z. | Trapped electron damping of geodesic acoustic mode [BibTeX] |
2010 | Physics of Plasmas Vol. 17(7), pp. 072502-+ |
DOI URL | |

BibTeX:
@article{zhanghs10a, author = {Zhang, H.~S. and Lin, Z.}, title = {Trapped electron damping of geodesic acoustic mode}, journal = {Physics of Plasmas}, year = {2010}, volume = {17}, number = {7}, pages = {072502-+}, url = {http://phoenix.ps.uci.edu/zlin/bib/zhanghs10a.pdf}, doi = {http://dx.doi.org/10.1063/1.3447879} } |
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Zhang, W., Lin, Z. & Chen, L. | Transport of Energetic Particles by Microturbulence in Magnetized Plasmas [BibTeX] |
2008 | Phys. Rev. Lett. Vol. 101(9), pp. 095001 |
DOI URL | |

BibTeX:
@article{Zhang08a, author = {Zhang, Wenlu and Lin, Zhihong and Chen, Liu}, title = {Transport of Energetic Particles by Microturbulence in Magnetized Plasmas}, journal = {Phys. Rev. Lett.}, publisher = {American Physical Society}, year = {2008}, volume = {101}, number = {9}, pages = {095001}, url = {http://phoenix.ps.uci.edu/zlin/bib/zhangwl08b.pdf}, doi = {http://dx.doi.org/10.1103/PhysRevLett.101.095001} } |
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Zonca, F. | The physics of burning plasmas in toroidal magnetic field devices [BibTeX] |
2008 | Intern. J. Modern Phys. A Vol. 23, pp. 1165 |
URL | |

BibTeX:
@article{Zonca08b, author = {F. Zonca}, title = {The physics of burning plasmas in toroidal magnetic field devices}, journal = {Intern. J. Modern Phys. A}, year = {2008}, volume = {23}, pages = {1165}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Zonca08a.pdf} } |
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Zonca, F. & Chen, L. | Radial structures and nonlinear excitation of geodesic acoustic modes | 2008 | EPL (Europhysics Letters) Vol. 83(3), pp. 35001 |
URL | |

Abstract: Geodesic acoustic modes (GAM) are shown to constitute a continuous spectrum due to radial inhomogeneities. The importance and theoretical as well as experimental implications of this fact are discussed in this work. The existence of a singular layer causes GAM to mode convert to short-wavelength kinetic GAM (KGAM) via finite ion Larmor radii; analogous to kinetic Alfvén waves (KAW). Furthermore, it is shown that KGAM can be nonlinearly excited by drift-wave (DW) turbulence via 3-wave parametric interactions, and the resultant driven-dissipative nonlinear system exhibits typical prey-predator self-regulatory dynamics, consistent with recent experimental observations on HL-2A. The degeneracy of GAM/KGAM with beta-induced Alfvén eigenmodes (BAE) is demonstrated and discussed, with emphasis on its important role in the complex self-organized behaviors of burning plasmas. |
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BibTeX:
@article{Zonca08a, author = {F. Zonca and L. Chen}, title = {Radial structures and nonlinear excitation of geodesic acoustic modes}, journal = {EPL (Europhysics Letters)}, year = {2008}, volume = {83}, number = {3}, pages = {35001}, url = {http://phoenix.ps.uci.edu/GSEP/pubs/Zonca08b.pdf} } |
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Zonca, F., Chen, L., Botrugno, A., Buratti, P., Cardinali, A., Cesario, R., Ridolfini, V.P. & contributors, J.-E. | High-frequency fishbones at JET: theoretical interpretation of experimental observations | 2009 | Nuclear Fusion Vol. 49(8), pp. 085009 |
URL | |

Abstract: The existence of fishbone fluctuations at frequencies comparable to those of geodesic acoustic modes (GAM) and beta induced Alfvén eigenmodes (BAE) has been demonstrated theoretically in a recent work (Zonca et al 2007 Nucl. Fusion [/0029-5515/47] 47 1588 ). Here, we show that observation of fishbones at unexpectedly high frequencies in JET (Nabais et al 2005 Phys. Plasmas 12 102509) is well interpreted as experimental evidence of high (GAM/BAE range) frequency fishbones and discuss the insights concerning both supra-thermal particles as well as thermal plasma properties that can be obtained from experimental observations. |
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BibTeX:
@article{Zonca09a, author = {F. Zonca and L. Chen and A. Botrugno and P. Buratti and A. Cardinali and R. Cesario and V. Pericoli Ridolfini and JET-EFDA contributors}, title = {High-frequency fishbones at JET: theoretical interpretation of experimental observations}, journal = {Nuclear Fusion}, year = {2009}, volume = {49}, number = {8}, pages = {085009}, url = {http://phoenix.ps.uci.edu/gsep/pubs/Zonca09b.pdf} } |

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