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403 results on '"Fonck, R. J."'

2. Effect of magnetic perturbations on turbulence-flow dynamics at the L-H transition on DIII-D

Author

Kriete, D. M., McKee, G. R., Schmitz, L., Smith, D. R., Yan, Z., Morton, L. A., and Fonck, R. J.

Subjects
Physics - Plasma Physics
Abstract

Detailed 2D turbulence measurements from the DIII-D tokamak provide an explanation for how resonant magnetic perturbations (RMPs) raise the L-H power threshold $P_\textrm{LH}$ [P. Gohil et al., Nucl. Fusion 51, 103020 (2011)] in ITER-relevant, low rotation, ITER-similar-shape plasmas with favorable ion $\nabla B$ direction. RMPs simultaneously raise the turbulence decorrelation rate $\Delta \omega_D$ and reduce the flow shear rate $\omega_\textrm{shear}$ in the stationary L-mode state preceding the L-H transition, thereby disrupting the turbulence shear suppression mechanism. RMPs also reduce the Reynolds stress drive for poloidal flow, contributing to the reduction of $\omega_\textrm{shear}$ On the ~100 {\mu}s timescale of the L-H transition, RMPs reduce Reynolds-stress-driven energy transfer from turbulence to flows by an order of magnitude, challenging the energy depletion theory for the L-H trigger mechanism. In contrast, non-resonant magnetic perturbations, which do not significantly affect $P_\textrm{LH}$, do not affect $\Delta \omega_D$ and only slightly reduce $\omega_\textrm{shear}$ and Reynolds-stress-driven energy transfer., Comment: The following article has been submitted to Physics of Plasmas

Published
2020
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6. Fusion Product Measurements in D-T Plasmas in TFTR

Author

Johnson, L. C., Barnes, C. W., Bell, R. E., Bitter, M., Budny, R. V., Bush, C. E., Darrow, D. S., Duong, H. H., Efthimion, P. C., Fisher, R. K., Fonck, R. J., Herrmann, H. W., Jassby, D. L., Krasilnikov, A. V., McKee, G. R., Medley, S. S., Osakabe, M., Petrov, M. P., Roquemore, A. L., Sasao, M., Sesnic, S., Stratton, B. C., Synakowski, E. J., von Goeler, S., Zweben, S. J., Stott, Peter E., editor, Gorini, Giuseppe, editor, and Sindoni, Elio, editor

Published
1996
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7. Initial characterization of electron temperature and density profiles in PEGASUS spherical tokamak discharges driven solely by local helicity injection

Author

Bodner, G. M., primary, Bongard, M. W., additional, Fonck, R. J., additional, Goetz, J. A., additional, Nornberg, M. D., additional, Pierren, C., additional, Reusch, J. A., additional, Rhodes, A. T., additional, Richner, N. J., additional, Rodriguez Sanchez, C., additional, Schaefer, C. E., additional, and Weberski, J. D., additional

Published
2021
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17. Non-inductively driven tokamak plasmas at near-unity βt in the P toroidal experiment

Author

Reusch, J. A., Bodner, G. M., Bongard, M. W., Burke, M. G., Fonck, R. J., Pachicano, J. L., Perry, J. M., Pierren, C., Rhodes, A. T., Richner, N. J., Rodriguez Sanchez, C., Schlossberg, D. J., and Weberski, J. D.

Subjects
Physics, Toroid, Tokamak, Magnetic reconnection, Plasma, Spherical tokamak, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Nuclear physics, law, Beta (plasma physics), 0103 physical sciences, Pegasus Toroidal Experiment, 010306 general physics, Current density
Abstract

A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance li, high elongation κ, and high toroidal and normalized beta ( βt and βN) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low li. The low aspect ratio ( R0/a∼1.2) of Pegasus allows access to high κ and high normalized plasma currents ( IN=Ip/aBT>14). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ∼100% is achieved. These high βt discharges disrupt at the ideal no-wall β limit at βN∼7.

Published
2018
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21. Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment

Author

Reusch, J. A., primary, Bodner, G. M., additional, Bongard, M. W., additional, Burke, M. G., additional, Fonck, R. J., additional, Pachicano, J. L., additional, Perry, J. M., additional, Pierren, C., additional, Rhodes, A. T., additional, Richner, N. J., additional, Rodriguez Sanchez, C., additional, Schlossberg, D. J., additional, and Weberski, J. D., additional

Published
2018
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30. Non-inductively driven tokamak plasmas at near-unity <italic>βt</italic> in the Pegasus toroidal experiment.

Author

Reusch, J. A., Bodner, G. M., Bongard, M. W., Burke, M. G., Fonck, R. J., Pachicano, J. L., Perry, J. M., Pierren, C., Rhodes, A. T., Richner, N. J., Rodriguez Sanchez, C., Schlossberg, D. J., and Weberski, J. D.

Subjects
TOKAMAKS, TOROIDAL plasma, HELICITY of nuclear particles, ELECTRIC inductance, PLASMA currents
Abstract

A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓ i , high elongation κ , and high toroidal and normalized beta ( β t and β N ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓ i . The low aspect ratio ( R 0 / a ∼ 1.2 ) of Pegasus allows access to high κ and high normalized plasma currents ( I N = I p / a B T > 14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high β t plasmas. Equilibrium analyses indicate that β t up to ∼100% is achieved. These high β t discharges disrupt at the ideal no-wall β limit at β N ∼ 7. [ABSTRACT FROM AUTHOR]

Published
2018
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31. Ultra-fast charge exchange spectroscopy for turbulent ion temperature fluctuation measurements on the DIII-D tokamak (invited)

Author

Uzun Kaymak, İlker Ümit, Fonck, R. J., McKee, G. R., and OpenMETU

Subjects
Detector
Abstract

A novel two-channel, high throughput, high efficiency spectrometer system has been developed to measure impurity ion temperature and toroidal velocity fluctuations associated with long-wavelength turbulence and other plasma instabilities. The spectrometer observes the emission of the n = 8-7 hydrogenic transition of C+5 ions (lambda(air) = 529.06 nm) resulting from charge exchange reactions between deuterium heating beams and intrinsic carbon. Novel features include a large, prism-coupled high-dispersion, volume-phase-holographic transmission grating and high-quantum efficiency, high-gain, low-noise avalanche photodiode detectors that sample emission at 1 MHz. This new diagnostic offers an order-of-magnitude increase in sensitivity compared to earlier ion thermal turbulence measurements. Increased sensitivity is crucial for obtaining enough photon statistics from plasmas with much less impurity content. The irreducible noise floor set by photon statistics sets the ultimate sensitivity to plasma fluctuations. Based on themeasured photon flux levels for the entire spectral line, photon noise levels for (T) over tilde (i)/T-i and (V) over tilde (i)/V-i of similar to 1% are expected, while statistical averaging over long data records enables reduction in the detectable plasma fluctuation levels to values less than that. Broadband ion temperature fluctuations are observed to near 200 kHz in an L-mode discharge. Cross-correlation with the local beam emission spectroscopy measurements demonstrates a strong coupling of the density and temperature fields, and enables the cross-phase measurements between density and ion temperature fluctuations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733548]

Published
2012

34. Deuterium-tritium plasmas in novel regimes in the Tokamak Fusion Test Reactor

Author

Bell, M. G., Batha, S., Beer, M., Bell, R. E., Belov, A., Berk, H., Bemabei, S., Bitter, M., Breizman, B., Bretz, N. L., Budny, R., Bush, C. E., Callen, J., Cauffman, S., Chang, C. S., Chang, Z., Cheng, C. Z., Darrow, D. S., Dendy, R. O., Dorland, W., Duong, H., Efthimion, P. C., Ernst, D., Evenson, H., Fisch, N. J., Fisher, R., Fonck, R. J., Fredrickson, E. D., Fu, G. Y., Furth, H. P., Gorelenkov, N. N., Goloborodko, V. Y., Grek, B., Grisham, L. R., Hammett, G. W., Hawryluk, R. J., Heidbrink, W., Herrmann, H. W., Hermann, M. C., Hill, K. W., Hogan, J., Hooper, B., Hosea, J. C., Houlberg, W. A., Hughes, M., Jassby, D. L., Jobes, F. C., Johnson, D. W., Kaita, R., Kaye, S., Kesner, J., Kim, J. S., Kissick, M., Krasilnikov, A. V., Kugel, H., Kumar, A., Lam, N. T., Lamarche, P., Leblanc, B., Levinton, F. M., Ludescher, C., Machuzak, J., Majeski, R. P., Manickam, J., Mansfield, D. K., Mauel, M., Mazzucato, E., Mcchesney, J., Mccune, D. C., Mckee, G., Mcguire, K. M., Meade, D. M., Medley, S. S., Mikkelsen, D. R., Mirnov, S. V., Mueller, D., Nagayama, Y., Navratil, G. A., Nazikian, R., Okabayashi, M., Osakabe, M., Owens, D. K., Park, H. K., Park, W., Paul, S. F., Petrov, M. P., Phillips, C. K., Phillips, M., Phillips, P., Ramsey, A. T., Rice, B., Redi, M. H., Rewoldt, G., Reznik, S., Roquemore, A. L., Rogers, J., Ruskov, E., Sabbagh, S. A., Sasao, M., Schilling, G., Schmidt, G. L., Scott, S. D., Semenov, I., Senko, T., Skinner, C. H., Stevenson, T., Strait, E. J., Stratton, B. C., Strachan, J. D., Stodiek, W., Synakowski, E., Takahashi, H., Tang, W., Taylor, G., Thompson, M. W., Vongoeler, S., Vonhalle, A., Walters, R. T., Wang, S., White, R., Wieland, R. M., William Dorland, Wilson, J. R., Wong, K. L., Wurden, G. A., Yamada, M., Yavorski, V., Young, K. M., Zakharov, L., Zarnstorff, M. C., and Zweben, S. J.

Published
1997

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