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Your search keyword '"G. R. McKee"' showing total 5 results
Start Over Author "G. R. McKee" Journal physical review letters
5 results on '"G. R. McKee"'

1. Regulation of Alfvén Eigenmodes by Microturbulence in Fusion Plasmas

Author

P. Liu, X. Wei, Z. Lin, G. Brochard, G. J. Choi, W. W. Heidbrink, J. H. Nicolau, and G. R. McKee

Subjects
General Physics and Astronomy
Abstract

Global gyrokinetic simulations of mesoscale reversed shear Alfven eigenmodes (RSAE) excited by energetic particles (EP) in fusion plasmas find that RSAE amplitude and EP transport are much higher than experimental levels at nonlinear saturation, but quickly diminish to very low levels after the saturation if background microturbulence is artificially suppressed. In contrast, in simulations coupling micro-meso scales, the RSAE amplitude and EP transport decrease drastically at the initial saturation but later increases to the experimental levels in the quasisteady state with bursty dynamics due to regulation by thermal ion temperature gradient (ITG) microturbulence. The quasisteady state EP transport is larger for a stronger microturbulence. The RSAE amplitude in the quasisteady state ITG-RSAE turbulence from gyrokinetic simulations, for the first time, agrees very well with experimental measurements.

Published
2021

2. Observation of the L-H confinement bifurcation triggered by a turbulence-driven shear flow in a tokamak plasma

Author

Z, Yan, G R, McKee, R, Fonck, P, Gohil, R J, Groebner, and T H, Osborne

Abstract

Comprehensive 2D turbulence and eddy flow velocity measurements on DIII-D demonstrate a rapidly increasing turbulence-driven shear flow that develops ∼100 μs prior to the low-confinement (L mode) to high-confinement (H mode) transition and appears to trigger it. These changes are localized to a narrow layer 1-2 cm inside the magnetic boundary. Increasing heating power increases the Reynolds stress, the energy transfer from turbulence to the poloidal flow, and the edge flow shearing rate that then exceeds the decorrelation rate, suppressing turbulence and triggering the transition.

Published
2013

3. Confined Alpha Distribution Measurements in a Deuterium-Tritium Tokamak Plasma

Author

David W. Johnson, G. Taylor, A. T. Ramsey, B. C. Stratton, G. R. McKee, R.E. Bell, C.E. Bush, R.V. Budny, E. J. Synakowski, B. Grek, R.J. Fonck, and Hae-Woong Park

Subjects
Physics, Tokamak, General Physics and Astronomy, Alpha particle, Plasma, Spectral line, law.invention, Distribution function, Thermalisation, Deuterium, Physics::Plasma Physics, law, Atomic physics, Energy (signal processing)
Abstract

Fusion-produced alpha particles with energy {le}0.7 MeV have been spectroscopically observed in the core of a deuterium-tritium plasma in the TFTR tokamak at alpha densities of 3{times}10{sup 16}m{sup {minus}3}. During a sawtooth-free discharge, the measured energy spectra at {ital r}/{ital a}=0.3 are in good agreement with those predicted on the basis of collisional transport. Time-resolved measurements during the alpha thermalization after alpha source turn-off show decay of the distribution function to lower energies consistent with the classical slowing-down time of 0.5 s.

Published
1995

4. Fusion power production from TFTR plasmas fueled with deuterium and tritium

Author

K. L. Wong, Takeo Nishitani, R. Newman, R. M. Wieland, M. Leonard, D. S. Darrow, R.E. Bell, K. M. McGuire, G. A. Wurden, G. Pearson, G. Coward, M. P. Petrov, Manfred Bitter, M. H. Redi, Joseph Snipes, A.C. Janos, H. Adler, H. W. Herrmann, W. R. Blanchard, J.M. McChesney, C. K. Phillips, A. Martin, M. Caorlin, James R. Wilson, A. T. Ramsey, Harold P. Furth, Fred Levinton, C. Vannoy, Gregory W. Hammett, R. T. Walters, N. Fromm, G. Schilling, D. K. Owens, P. H. LaMarche, J. H. Kamperschroer, D. R. Mikkelsen, S. von Goeler, Cris W. Barnes, S. D. Scott, C. Ancher, S. H. Batha, M. G. Bell, B. McCormack, P. C. Efthimion, Guoyong Fu, W. Park, A. von Halle, Masaki Osakabe, M. Tuszewski, H.H. Duong, G. R. McKee, John B Wilgen, B.P. LeBlanc, D.C. McCune, C. Gentile, N. T. Lam, R. K. Fisher, J. Machuzak, S. Cauffman, S. Pitcher, F. C. Jobes, M. Oldaker, A. Nagy, Kenneth M. Young, S. J. Zweben, M. E. Thompson, S.A. Sabbagh, R. J. Fonck, J.F. Schivell, Chio-Zong Cheng, William Heidbrink, E. Perry, B. C. Stratton, J. D. Strachan, Mamiko Sasao, N. N. Gorelenkov, E.D. Fredrickson, P. Alling, M. Norris, D. Ashcroft, C.E. Bush, J. E. Stevens, R. Durst, D.R. Ernst, Michael Loughlin, H.W. Kugel, L. C. Johnson, S.F. Paul, E. Mazzucato, M. C. Zarnstorff, Robert Budny, David W. Johnson, E. J. Synakowski, Richard Majeski, J. L. Terry, G. R. Hanson, J. Hosea, E. Ruskov, Dale Meade, J. H. Rogers, Z. Chang, M. Murakami, A. L. Roquemore, G. Barnes, N. L. Bretz, D. Voorhees, L. Dudek, S. S. Medley, D. L. Jassby, G. Taylor, J.L. Anderson, K. W. Hill, D. Mueller, B. Grek, Masaaki Yamada, T. O’Connor, D.K. Mansfield, L. R. Grisham, Hyeon K. Park, R. Camp, E.S. Marmar, David A Rasmussen, M. Williams, R. Sissingh, H. Anderson, T. Stevenson, G. L. Schmidt, D. W. Roberts, H. Hsuan, R. Rossmassler, William Tang, Raffi Nazikian, R. J. Hawryluk, C.H. Skinner, J. DeLooper, and J. Collins

Subjects
Nuclear physics, Physics, Deuterium, Lawson criterion, General Physics and Astronomy, Tritium, Alpha particle, Plasma, Fusion power, Atomic physics, Charged particle, Ion
Abstract

Peak fusion power production of 6.2 ± 0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total power of 29.5 MW. These plasmas have an inferred central fusion alpha particle density of 1.2 x 1017 m ₋3 without the appearance of either disruptive magnetohydrodynamics events or detectable changes in Alfven wave activity. The measured loss rate of energetic alpha particles agreed with the approximately 5% losses expected from alpha particles which are born on unconfined orbits.

Published
1994

5. Confinement and heating of a deuterium-tritium plasma

Author

P. C. Efthimion, E. J. Synakowski, Guoyong Fu, J.M. McChesney, C. K. Phillips, M. Caorlin, R. Newman, William Heidbrink, E.D. Fredrickson, Gregory W. Hammett, R. M. Wieland, J. E. Stevens, C. Gentile, S. Cauffman, G. Barnes, M. Tuszewski, L. Dudek, Manfred Bitter, E. Perry, N. T. Lam, Masaki Osakabe, N. L. Bretz, K. L. Wong, R. K. Fisher, J. DeLooper, D. Voorhees, L. C. Johnson, David W. Johnson, J.F. Schivell, G. R. Hanson, F. C. Jobes, J. Hosea, Chio-Zong Cheng, D. S. Darrow, J. D. Strachan, Mamiko Sasao, James R. Wilson, E. Ruskov, B. Grek, Richard Majeski, S.F. Paul, K. M. McGuire, Dale Meade, J. H. Rogers, J. Machuzak, G. A. Wurden, E.S. Marmar, R. Sissingh, R. T. Walters, Z. Chang, H. W. Herrmann, T. Stevenson, H. Anderson, G. Schilling, J. H. Kamperschroer, M. H. Redi, Masaaki Yamada, A. von Halle, W. R. Blanchard, D. L. Jassby, J.L. Anderson, Takeo Nishitani, C. Ancher, R. Camp, M. Oldaker, D. Mueller, John B Wilgen, D. W. Roberts, William Tang, R. Durst, J.L. Terry, N. N. Gorelenkov, P. H. LaMarche, D. R. Mikkelsen, David A Rasmussen, R. J. Hawryluk, M. Leonard, C.H. Skinner, T. O’Connor, A. L. Roquemore, Kenneth M. Young, L. R. Grisham, R.E. Bell, M. E. Thompson, D.K. Mansfield, D. Ashcroft, S. S. Medley, E. Mazzucato, G. Taylor, K. W. Hill, B.P. LeBlanc, Raffi Nazikian, G. Pearson, G. Coward, A. Nagy, M. P. Petrov, Cris W. Barnes, S. D. Scott, B. C. Stratton, S.A. Sabbagh, R. J. Fonck, Joseph Snipes, C. Vannoy, Stewart Zweben, R.V. Budny, D.R. Ernst, H.W. Kugel, M. Norris, C.E. Bush, N. Fromm, D. K. Owens, M. C. Zarnstorff, W. Park, Hyeon K. Park, J. Collins, Harold P. Furth, M. Williams, H. Hsuan, M. G. Bell, B. McCormack, H.H. Duong, G. R. McKee, A. T. Ramsey, G. L. Schmidt, R. Rossmassler, D.C. McCune, P. Alling, Michael Loughlin, M. Murakami, Fred Levinton, S. von Goeler, H. Adler, A. Martin, A.C. Janos, S. H. Batha, and S. Pitcher

Subjects
inorganic chemicals, Physics, Deuterium, Lawson criterion, technology, industry, and agriculture, General Physics and Astronomy, Electron temperature, Tritium, Plasma diagnostics, Plasma, Atomic physics, Tokamak Fusion Test Reactor, Ion
Abstract

The Tokamak Fusion Test Reactor (TFTR) has performed initial high-power experiments with the plasma fueled by deuterium and tritium to nominally equal densities. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by ~20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by α-particles.

Published
1994

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