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Journal Articles

Multi-phase simulation of fast ion profile flattening due to Alfv$'e$n eigenmodes in a DIII-D experiment

Todo, Yasushi*; Van Zeeland, M. A.*; Bierwage, A.; Heidbrink, W. W.*

Nuclear Fusion, 54(10), p.104012_1 - 104012_13, 2014/10

 Times Cited Count:31 Percentile:10.3(Physics, Fluids & Plasmas)

Journal Articles

Dynamics of energetic particle driven modes and MHD modes in wall-stabilized high-$$beta$$ plasmas on JT-60U and DIII-D

Matsunaga, Go; Okabayashi, Michio*; Aiba, Nobuyuki; Boedo, J. A.*; Ferron, J. R.*; Hanson, J. M.*; Hao, G. Z.*; Heidbrink, W. W.*; Holcomb, C. T.*; In, Y.*; et al.

Nuclear Fusion, 53(12), p.123022_1 - 123022_13, 2013/12

 Times Cited Count:2 Percentile:88.34(Physics, Fluids & Plasmas)

Journal Articles

Energetic ion transport by microturbulence is insignificant in tokamaks

Pace, D. C.*; Austin, M. E.*; Bass, E. M.*; Budny, R.*; Heidbrink, W. W.*; Hillesheim, J. C.*; Holcomb, C. T.*; Gorelenkova, M.*; Grierson, B. A.*; McCune, D. C.*; et al.

Physics of Plasmas, 20(5), p.056108_1 - 056108_18, 2013/05

 Times Cited Count:28 Percentile:13.13(Physics, Fluids & Plasmas)

Energetic ion transport due to microturbulence is investigated in MHD-quiescent plasmas by way of neutral beam injection in the DIII-D tokamak. A range of on-axis and off-axis beam injection scenarios are employed to vary relevant parameters such as the character of the background microturbulence and the value of Eb/Te, where Eb is the energetic ion energy and Te the electron temperature. In all cases it is found that any transport enhancement due to microturbulence is too small to observe experimentally. These transport effects are modeled using numerical and analytic expectations that calculate the energetic ion diffusivity due to microturbulence. It is determined that energetic ion transport due to coherent modes, including possible reductions in neutral beam current drive, is a considerably larger effect and should therefore be considered more important for ITER.

Journal Articles

Dynamics of energetic particle driven modes and MHD modes in wall-stabilized high beta plasmas on JT-60U and DIII-D

Matsunaga, Go; Okabayashi, Michio*; Aiba, Nobuyuki; Boedo, J. A.*; Ferron, J. R.*; Hanson, J. M.*; Hao, G. Z.*; Heidbrink, W. W.*; Holcomb, C. T.*; In, Y.*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Journal Articles

ITER test blanket module error field simulation experiments at DIII-D

Schaffer, M. J.*; Snipes, J. A.*; Gohil, P.*; de Vries, P.*; Evans, T. E.*; Fenstermacher, M. E.*; Gao, X.*; Garofalo, A. M.*; Gates, D. A.*; Greenfield, C. M.*; et al.

Nuclear Fusion, 51(10), p.103028_1 - 103028_11, 2011/10

 Times Cited Count:32 Percentile:15.21(Physics, Fluids & Plasmas)

Experiments at DIII-D investigated the effects of ferromagnetic error fields similar to those expected from proposed ITER Test Blanket Modules (TBMs). Studied were effects on: plasma rotation and locking; confinement; L-H transition; edge localized mode (ELM) suppression by resonant magnetic perturbations; ELMs and the H-mode pedestal; energetic particle losses; and more. The experiments used a 3-coil mock-up of 2 magnetized ITER TBMs in one ITER equatorial port. The experiments did not reveal any effect likely to preclude ITER operations with a TBM-like error field. The largest effect was slowed plasma toroidal rotation v across the entire radial profile by as much as $$Delta v/v_{0} sim 50%$$ via non-resonant braking. Changes to global $$Delta n/n_{0}$$, $$Delta v/v_{0}$$ and $$Delta H_{98}/H_{98,0}$$ were $$sim$$3 times smaller. These effects are stronger at higher $$beta$$ and lower $$v_{0}$$. Other effects were smaller.

Journal Articles

Experimental investigation and validation of neutral beam current drive for ITER through ITPA joint experiments

Suzuki, Takahiro; Akers, R.*; Gates, D. A.*; G$"u$nter, S.*; Heidbrink, W. W.*; Hobirk, J.*; Luce, T. C.*; Murakami, Masanori*; Park, J. M.*; Turnyanskiy, M.*; et al.

Nuclear Fusion, 51(8), p.083020_1 - 083020_8, 2011/08

 Times Cited Count:15 Percentile:37.88(Physics, Fluids & Plasmas)

Joint experiments investigating the off-axis neutral beam current drive (NBCD) capability to be utilized for advanced operation scenario development in ITER was conducted in 5 tokamaks (AUG, DIII-D, JT-60U, MAST and NSTX) through the ITPA. We discuss results obtained in the joint experiments, where the toroidal field, $$B$$$$_{rm t}$$, covered 0.3-3.7 T, the plasma current, $$I$$$$_{rm p}$$, 0.6-1.2 MA, and the beam energy, Eb, 67-350 keV. A current profile broadened by off-axis NBCD was observed in MAST. In DIII-D, good agreement between the measured and calculated NB driven current profile was observed. In JT-60U, agreement between measured and calculated NBCD location was obtained, when the NBCD location (0.3-0.6 in $$r$$/$$a$$), heating power (6-13 MW), triangularity $$d$$ (0.25-0.45), and $$E$$$$_{b}$$ (85 and 350 keV) were widely scanned. In AUG (at low $$delta$$$$ sim$$ 0.2) and DIII-D, introduction of a fast ion diffusion coefficient of $$D$$$$_{rm b}$$ 0.3-0.5 m$$^2$$/s in the calculation gave better agreement at high heating power (5 and 7.2 MW), suggesting anomalous transport of fast ions by turbulence. It was found through these ITPA joint experiments that NBCD related physics quantities reasonably agree with calculations (with $$D$$$$_{rm b}$$ = 0-0.5 m$$^2$$/s) in all devices when there is no MHD activity except ELMs. Proximity of measured off-axis beam driven current to the corresponding calculation with $$D$$$$_{rm b}$$ = 0 has been discussed for ITER in terms of a theoretically predicted scaling of fast-ion diffusion that depends on $$E$$$$_{rm b}$$/$$T$$$$_{rm e}$$ for electrostatic turbulence or $$beta$$$$_{rm t}$$ for electromagnetic turbulence.

Journal Articles

Experimental investigation and validation of neutral beam current drive for ITER through ITPA joint experiments

Suzuki, Takahiro; Akers, R.*; Gates, D. A.*; G$"u$nter, S.*; Heidbrink, W. W.*; Hobirk, J.*; Luce, T. C.*; Murakami, Masanori*; Park, J. M.*; Turnyanskiy, M.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2010/10

Joint experiments investigating the off-axis neutral beam current drive (NBCD) capability to be utilized for advanced operation scenario development in ITER was conducted in 4 tokamaks (AUG, DIII-D, JT-60U and MAST) through the ITPA. We discuss results obtained in the joint experiments, where the toroidal field, Bt, covered 0.3-3.7 T, the plasma current, Ip, 0.6-1.2 MA, and the beam energy, Eb, 67-350 keV. A current profile broadened by off-axis NBCD was observed in MAST. In DIII-D, good agreement between the measured and calculated NB driven current profile was observed. In JT-60U, agreement between measured and calculated NBCD location was obtained, when the NBCD location (0.3-0.6 in r/a), heating power (6-13 MW), triangularity d (0.25-0.45), and Eb (85 and 350 keV) were widely scanned. In AUG (at low d 0.2) and DIII-D, introduction of a fast ion diffusion coefficient of Db 0.3-0.5 m$$^2$$/s in the calculation gave better agreement at high heating power (5 and 7.2 MW), suggesting anomalous transport of fast ions by turbulence. It was found through these ITPA joint experiments that NBCD related physics quantities reasonably agree with calculations (with Db=0-0.5 m$$^2$$/s) in all devices when there is no MHD activity except ELMs.

Journal Articles

Validation of on- and off-axis neutral beam current drive against experiment in DIII-D

Park, J. M.*; Murakami, Masanori*; Petty, C. C.*; Heidbrink, W. W.*; Osborne, T. H.*; Holcomb, C. T.*; Van Zeeland, M. A.*; Prater, R.*; Luce, T. C.*; Wade, M. R.*; et al.

Physics of Plasmas, 16(9), p.092508_1 - 092508_10, 2009/09

 Times Cited Count:17 Percentile:38.91(Physics, Fluids & Plasmas)

Neutral beam current drive (NBCD) experiments in DIII-D using vertically shifted plasmas to move the current drive away from the axis have clearly demonstrated robust off-axis NBCD. Time-dependent measurements of magnetic pitch angles by the motional Stark effect diagnostic are used to obtain the evolution of the poloidal magnetic flux, which indicates a broad off-axis NBCD profile with a peak at about half the plasma radius. In most cases, the measured off-axis NBCD profile is consistent with calculations using an orbit-following Monte-Carlo code for the beam ion slowing down including finite-orbit effects, provided there is no large-scale MHD activity such as Alfv$'e$n eigenmodes modes or sawteeth. Good agreement is found between the measured pitch angles and those from simulations using transport-equilibrium codes. Two-dimensional image of Doppler-shifted fast ion D$$alpha$$ light emitted by neutralized energetic ions shows clear evidence for a hollow profile of beam ion density, consistent with classical beam ion slowing down. The magnitude of off-axis NBCD is sensitive to the alignment of the beam injection relative to the helical pitch of the magnetic field lines. If the signs of B and I yield the proper helicity, both measurement and calculation indicate that the efficiency is as good as on-axis NBCD because the increased fraction of trapped electrons reduces the electron shielding of the injected ion current, in contrast with electron current drive schemes where the trapping of electrons degrades the efficiency. The measured off-axis NBCD increases approximately linearly with the injection power, although a modest amount of fast ion diffusion is needed to explain an observed difference in the NBCD profile between the measurement and the calculation at high injection power.

Journal Articles

Off-axis neutral beam current drive for advanced scenario development in DIII-D

Murakami, Masanori*; Park, J. M.*; Petty, C. C.*; Luce, T. C.*; Heidbrink, W. W.*; Osborne, T. H.*; Prater, R.*; Wade, M. R.*; Anderson, P. M.*; Austin, M. E.*; et al.

Nuclear Fusion, 49(6), p.065031_1 - 065031_8, 2009/06

 Times Cited Count:38 Percentile:15.02(Physics, Fluids & Plasmas)

Modification of the two existing DIII-D neutral beam lines is planned to allow vertical steering to provide off-axis neutral beam current drive (NBCD) peaked as far off-axis as half the plasma minor radius. New calculations for a downward-steered beam indicate strong current drive with good localization off-axis so long as the toroidal magnetic field, BT, and the plasma current, Ip, point in the same direction. This is due to good alignment of neutral beam injection (NBI) with the local pitch of the magnetic field lines. This model has been tested experimentally on DIII-D by an injecting equatorially-mounted NBs into reduced size plasmas that are vertically displaced with respect to the vessel midplane. The existence of off-axis NBCD is evident in the changes seen in sawtooth behavior in the internal inductance. By shifting the plasma upward or downward, or by changing the sign of the toroidal field, measured off-axis NBCD profiles measured with motional Stark effect data and internal loop voltage show a difference in amplitude (40%-45%) consistent with predicted differences predicted by the changed NBI alignment with respect to the helicity of the magnetic field lines. The effects of NB injection direction relative to field line helicity can be large even in ITER: off-axis NBCD can be increased by more than 20% if the BT direction is reversed. Modification of the DIII-D NB system will strongly support scenario development for ITER and future tokamaks as well as providing flexible scientific tools for understanding transport, energetic particles and heating and current drive.

Journal Articles

Progress in the ITER physics basis, 5; Physics of energetic ions

Fasoli, A.*; Gormezano, C.*; Berk, H. L.*; Breizman, B.*; Briguglio, S.*; Darrow, D. S.*; Gorelenkov, N.*; Heidbrink, W. W.*; Jaun, A.*; Konovalov, S. V.*; et al.

Nuclear Fusion, 47(6), p.S264 - S284, 2007/06

 Times Cited Count:330 Percentile:17.54(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Performance of the solid state neutral particle analyzer array on the national spherical torus experiment

Liu, D.*; Heidbrink, W. W.*; Darrow, D. S.*; Roquemore, A. L.*; Medley, S. S.*; Shinohara, Koji

Review of Scientific Instruments, 77(10), p.10F113_1 - 10F113_4, 2006/10

 Times Cited Count:17 Percentile:33.82(Instruments & Instrumentation)

The Solid State Neutral Particle Analyzer (SSNPA) array on the National Spherical Torus Experiment (NSTX) consists of four chords with tangency radii 60, 90, 100 and 120 cm that view across the three co-injection neutral beam lines. Each chord utilizes a silicon photodiode that is coupled to fast digitizers to measure the energy distribution of charge exchange fast neutral particles (30$$sim$$100keV). By the end of the NSTX 2005 run campaign, the noise in the SSNPA was reduced by half and reasonable signals were obtained with good electromagnetic shielding, fast digitization of raw signals, software-based pulse height analysis and pulse shape discrimination. Energy resolution of $$sim$$10 keV and time resolution of 2 ms have been achieved. Temporal evolutions of energetic neutral flux obtained with the SSNPA are in good agreement with those obtained with the E$$||$$B type Neutral Particle Analyzer. With these improvements, the SSNPA enables us to study MHD instabilities and fast ion redistribution.

Journal Articles

Energetic Particles in Magnetic Confinement Systems

Ninomiya, Hiromasa; Tobita, Kenji; Schneider, U.*; Martin, G.*; Heidbrink, W. W.*; Kolesnichenko, Ya. I.*

Nuclear Fusion, 40(7), p.1287 - 1291, 2000/07

 Times Cited Count:4 Percentile:27.5(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Discussion on experimental investigation and validation of neutral beam current drive for ITER through ITPA joint experiments

Suzuki, Takahiro; Akers, R.*; Gates, D. A.*; G$"u$nter, S.*; Heidbrink, W. W.*; Hobirk, J.*; Luce, T. C.*; Murakami, Masanori*; Park, J. M.*; Turnyanskiy, M.*; et al.

no journal, , 

Joint experiments investigating the off-axis neutral beam current drive (NBCD) capability to be utilized for advanced operation scenario development in ITER was conducted in 5 tokamaks (AUG, DIII-D, JT-60U, MAST and NSTX) through the ITPA. We discuss results obtained in the joint experiments, where the toroidal field, Bt, covered 0.3-3.7 T, the plasma current, Ip, 0.6-1.2 MA, and the beam energy, Eb, 67-350 keV. A current profile broadened by off-axis NBCD was observed in MAST. In DIII-D, good agreement between the measured and calculated NB driven current profile was observed. In JT-60U, agreement between measured and calculated NBCD location was obtained, when the NBCD location (0.3-0.6 in r/a), heating power (6-13 MW), triangularity d (0.25-0.45), and Eb (85 and 350 keV) were widely scanned. In AUG (at low d 0.2) and DIII-D, introduction of a fast ion diffusion coefficient of Db 0.3-0.5 m$$^2$$/s in the calculation gave better agreement at high heating power (5 and 7.2 MW), suggesting anomalous transport of fast ions by turbulence. It was found through these ITPA joint experiments that NBCD related physics quantities reasonably agree with calculations (with Db=0-0.5 m$$^2$$/s) in all devices when there is no MHD activity except ELMs.

Oral presentation

Results of ITER test blanket module mock-up experiments on DIII-D

Snipes, J. A.*; Schaffer, M. J.*; Gohil, P.*; de Vries, P.*; Fenstermacher, M. E.*; Evans, T. E.*; Gao, X. M.*; Garofalo, A.*; Gates, D. A.*; Greenfield, C. M.*; et al.

no journal, , 

A series of experiments was performed on DIII-D to mock-up the field that will be induced in a pair of ferromagnetic Test Blanket Modules (TBMs) in ITER to determine the effects of such error fields on plasma operation and performance. A set of coils producing both poloidal and toroidal fields was placed inside a re-entrant horizontal port close to the plasma. The coils produce a localized ripple due to the toroidal field (TF) + TBM up to 5.7%, which is more than four times that expected from a pair of representative 1.3 ton TBMs in ITER. The experiments show that the reduction in the toroidal rotation is sensitive to the ripple. On the other hand, the confinement is reduced by up to 15-18% for local ripple $$ge$$ 3% but is hardly affected at 1.7% local ripple.

Oral presentation

Dynamics of MHD modes in high-$$beta$$ tokamak plasmas

Matsunaga, Go; Okabayashi, Michio*; Aiba, Nobuyuki; Boedo, J. A.*; Ferron, J. R.*; Hanson, J. M.*; Hao, G. Z.*; Heidbrink, W. W.*; Holcomb, C. T.*; In, Y.*; et al.

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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