35 results on '"G. R. McKee"'
Search Results
2. Local measurements of the pedestal magnetic field profile throughout the ELM cycle on DIII-D
- Author
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M. G. Burke, R. J. Fonck, G. R. McKee, K. H. Burrell, S. R. Haskey, M. Knolker, F. M. Laggner, T. H. Osborne, B. S. Victor, and Z. Yan
- Subjects
Condensed Matter Physics - Abstract
New high speed localized measurements of the pedestal magnetic field during the edge localized mode (ELM) cycle of a DIII-D High confinement mode (H-mode) discharge indicate a temporally and spatial complex redistribution of the edge current density profile, jedge. The measurement technique extracts the magnetic field magnitude, B, via the spectral separation of Stark-split neutral beam radiation in the pedestal. Single spatial channel measurements from a novel spatial heterodyne spectrometer are validated in discharges with core current profile changes. The technique measures Stark-splitting changes that imply B changes as small as 1 mT with high time resolution (50 μs). At normalized poloidal flux [Formula: see text], B appears saturated in the inter-ELM period and then rapidly decreases in edge, B increases at the ELM crash. The behavior is consistent with a rapid collapse of jedge at the ELM crash and subsequent pedestal recovery. In some discharges, at [Formula: see text], changes in B are observed throughout the ELM cycle. In others, B recovers and is relatively stable until a few ms leading up to the next crash. Measurements of B during the H-mode transition show a large increase at [Formula: see text] with little change at [Formula: see text], consistent with the formation of the edge bootstrap current density peak. The [Formula: see text] spectrum is complicated by predicted changes to the Stark component intensities with density at the L–H transition.
- Published
- 2022
3. DIII-D research towards establishing the scientific basis for future fusion reactors
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L. Abadie, T. W. Abrams, J. Ahn, T. Akiyama, P. Aleynikov, J. Allcock, E. O. Allen, S. Allen, J. P. Anderson, A. Ashourvan, M. E. Austin, J. Bak, K. K. Barada, N. Barbour, L. Bardoczi, J. Barr, J. L. Barton, E. M. Bass, D. Battaglia, L. R. Baylor, J. Beckers, E. A. Belli, J. W. Berkery, N. Bertelli, J. M. Bialek, J. A. Boedo, R. L. Boivin, P. T. Bonoli, A. Bortolon, M. D. Boyer, R. E. Brambila, B. Bray, D. P. Brennan, A. R. Briesemeister, S. A. Bringuier, M. W. Brookman, D. L. Brower, B. R. Brown, W. D. Brown, D. Buchenauer, M. G. Burke, K. H. Burrell, J. Butt, R. J. Buttery, I. Bykov, J. M. Candy, J. M. Canik, N. M. Cao, L. Carbajal Gomez, L. C. Carlson, T. N. Carlstrom, T. A. Carter, W. Cary, L. Casali, M. Cengher, V. S. Chan, B. Chen, J. Chen, M. Chen, R. Chen, Xi Chen, W. Choi, C. Chrobak, C. Chrystal, R. M. Churchill, M. Cianciosa, C. F. Clauser, M. Clement, J. Coburn, C. S. Collins, A. W. Cooper, B. M. Covele, J. W. Crippen, N. A. Crocker, B. J. Crowley, A. Dal Molin, E. M. Davis, J. S. deGrassie, C. A. del-Castillo-Negrete, L. F. Delgado-Aparicio, A. Diallo, S. J. Diem, R. Ding, S. Ding, W. Ding, J. L. Doane, D. C. Donovan, J. Drake, D. Du, H. Du, X. Du, V. Duarte, J. D. Duran, N. W. Eidietis, D. Elder, D. Eldon, W. Elwasif, T. E. Ely, K. M. Eng, K. Engelhorn, D. Ennis, K. Erickson, D. R. Ernst, T. E. Evans, M. E. Fenstermacher, N. M. Ferraro, J. R. Ferron, D. F. Finkenthal, P. A. Fisher, B. Fishler, S. M. Flanagan, J. A. Fooks, L. Frassinetti, H. G. Frerichs, Y. Fu, T. Fulop, Q. Gao, F. Garcia, A. M. Garofalo, A. Gattuso, L. Giacomelli, E. M. Giraldez, C. Giroud, F. Glass, P. Gohil, X. Gong, Y. A. Gorelov, R. S. Granetz, D. L. Green, C. M. Greenfield, B. A. Grierson, R. J. Groebner, W. H. Grosnickle, M. Groth, H. J. Grunloh, H. Y. Guo, W. Guo, J. Guterl, R. C. Hager, S. Hahn, F. D. Halpern, H. Han, M. J. Hansink, J. M. Hanson, J. Harris, S. R. Haskey, D. R. Hatch, W. W. Heidbrink, J. Herfindal, D. N. Hill, M. D. Hill, E. T. Hinson, C. T. Holcomb, C. G. Holland, L. D. Holland, E. M. Hollmann, A. M. Holm, R. Hong, M. Hoppe, S. Houshmandyar, J. Howard, N. T. Howard, Q. Hu, W. Hu, H. Huang, J. Huang, Y. Huang, G. A. Hughes, J. Hughes, D. A. Humphreys, A. W. Hyatt, K. Ida, V. Igochine, Y. In, S. Inoue, A. Isayama, R. C. Isler, V. A. Izzo, M. R. Jackson, A. E. Jarvinen, Y. Jeon, H. Ji, X. Jian, R. Jimenez, C. A. Johnson, I. Joseph, D. N. Kaczala, D. H. Kaplan, J. Kates-Harbeck, A. G. Kellman, D. H. Kellman, C. E. Kessel, K. Khumthong, C. C. Kim, H. Kim, J. Kim, K. Kim, S. H. Kim, W. Kimura, J. R. King, A. Kirk, K. Kleijwegt, M. Knolker, A. Kohn, E. Kolemen, M. Kostuk, G. J. Kramer, P. Kress, D. M. Kriete, R. J. La Haye, F. M. Laggner, H. Lan, M. J. Lanctot, R. Lantsov, L. L. Lao, C. J. Lasnier, C. Lau, K. Law, D. Lawrence, J. Le, R. L. Lee, M. Lehnen, R. Leon, A. W. Leonard, M. Lesher, J. A. Leuer, G. Li, K. Li, K. T. Liao, Z. Lin, C. Liu, F. Liu, Y. Liu, Z. Liu, S. Loch, N. C. Logan, J. M. Lohr, J. Lore, T. C. Luce, N. C. Luhmann, R. Lunsford, C. Luo, Z. Luo, L. Lupin-Jimenez, A. Lvovskiy, B. C. Lyons, X. Ma, R. Maingi, M. A. Makowski, P. Mantica, M. Manuel, M. W. Margo, A. Marinoni, E. Marmar, W. C. Martin, R. L. Masline, G. K. Matsunaga, D. M. Mauzey, P. S. Mauzey, J. T. Mcclenaghan, G. R. Mckee, A. G. Mclean, H. S. Mclean, E. Meier, S. J. Meitner, J. E. Menard, O. Meneghini, G. Merlo, W. H. Meyer, D. C. Miller, W. J. Miller, C. P. Moeller, K. J. Montes, M. A. Morales, S. Mordijck, A. Moser, R. A. Moyer, S. A. Muller, S. Munaretto, M. Murakami, C. J. Murphy, C. M. Muscatello, C. E. Myers, A. Nagy, G. A. Navratil, R. M. Nazikian, A. L. Neff, T. F. Neiser, A. Nelson, P. Nguyen, R. Nguyen, J. H. Nichols, M. Nocente, R. E. Nygren, R. C. O'Neill, T. Odstrcil, S. Ohdachi, M. Okabayashi, E. Olofsson, M. Ono, D. M. Orlov, T. H. Osborne, N. A. Pablant, D. C. Pace, R. R. Paguio, A. Pajares Martinez, C. Pan, A. Pankin, J. M. Park, J. Park, Y. Park, C. T. Parker, S. E. Parker, P. B. Parks, C. J. Pawley, C. A. Paz-Soldan, W. A. Peebles, B. G. Penaflor, T. W. Petrie, C. C. Petty, Y. Peysson, A. Y. Pigarov, D. A. Piglowski, R. I. Pinsker, P. Piovesan, N. Piper, R. A. Pitts, J. D. Pizzo, M. L. Podesta, F. M. Poli, D. Ponce, M. Porkolab, G. D. Porter, R. Prater, J. Qian, O. Ra, T. Rafiq, R. Raman, C. Rand, G. C. Randall, J. M. Rauch, C. Rea, M. L. Reinke, J. Ren, Q. Ren, Y. Ren, T. L. Rhodes, J. Rice, T. D. Rognlien, J. C. Rost, W. L. Rowan, D. L. Rudakov, A. Salmi, B. S. Sammuli, C. M. Samuell, A. M. Sandorfi, C. Sang, O. J. Sauter, D. P. Schissel, L. Schmitz, O. Schmitz, E. J. Schuster, J. T. Scoville, A. Seltzman, I. Sfiligoi, M. Shafer, H. Shen, T. Shi, D. Shiraki, H. Si, D. R. Smith, S. P. Smith, J. A. Snipes, P. B. Snyder, E. R. Solano, W. M. Solomon, A. C. Sontag, V. A. Soukhanovskii, D. A. Spong, W. M. Stacey, G. M. Staebler, L. Stagner, B. Stahl, P. C. Stangeby, T. J. Stoltzfus-Dueck, D. P. Stotler, E. J. Strait, D. Su, L. E. Sugiyama, A. A. Sulyman, Y. Sun, C. Sung, W. A. Suttrop, Y. Suzuki, A. Svyatkovskiy, R. M. Sweeney, S. Taimourzadeh, M. Takechi, T. Tala, H. Tan, S. Tang, X. Tang, D. Taussig, G. Taylor, N. Z. Taylor, T. S. Taylor, A. Teklu, D. M. Thomas, M. B. Thomas, K. E. Thome, A. R. Thorman, R. A. Tinguely, B. J. Tobias, J. F. Tooker, H. Torreblanca, A. Torrezan De Sousa, G. L. Trevisan, D. Truong, F. Turco, A. D. Turnbull, E. A. Unterberg, P. Vaezi, P. J. Vail, M. A. Van Zeeland, M. Velasco Enriquez, M. C. Venkatesh, B. S. Victor, F. Volpe, M. R. Wade, M. L. Walker, J. R. Wall, G. M. Wallace, R. E. Waltz, G. Wang, H. Wang, Y. Wang, Z. Wang, F. Wang, S. H. Ward, J. G. Watkins, M. Watkins, W. P. Wehner, M. Weiland, D. B. Weisberg, A. S. Welander, A. E. White, R. B. White, D. Whyte, T. A. Wijkamp, R. Wilcox, T. Wilks, H. R. Wilson, A. Wingen, E. Wolfe, M. Wu, W. Wu, S. J. Wukitch, T. Xia, N. Xiang, B. Xiao, R. Xie, G. Xu, H. Xu, X. Xu, Z. Yan, Q. Yang, X. Yang, M. Yoshida, G. Yu, J. H. Yu, M. Yu, S. A. Zamperini, L. Zeng, B. Zhao, D. Zhao, H. Zhao, Y. Zhao, Y. Zhu, B. Zywicki, Abadie, L, Abrams, T, Ahn, J, Akiyama, T, Aleynikov, P, Allcock, J, Allen, E, Allen, S, Anderson, J, Ashourvan, A, Austin, M, Bak, J, Barada, K, Barbour, N, Bardoczi, L, Barr, J, Barton, J, Bass, E, Battaglia, D, Baylor, L, Beckers, J, Belli, E, Berkery, J, Bertelli, N, Bialek, J, Boedo, J, Boivin, R, Bonoli, P, Bortolon, A, Boyer, M, Brambila, R, Bray, B, Brennan, D, Briesemeister, A, Bringuier, S, Brookman, M, Brower, D, Brown, B, Brown, W, Buchenauer, D, Burke, M, Burrell, K, Butt, J, Buttery, R, Bykov, I, Candy, J, Canik, J, Cao, N, Carbajal Gomez, L, Carlson, L, Carlstrom, T, Carter, T, Cary, W, Casali, L, Cengher, M, Chan, V, Chen, B, Chen, J, Chen, M, Chen, R, Chen, X, Choi, W, Chrobak, C, Chrystal, C, Churchill, R, Cianciosa, M, Clauser, C, Clement, M, Coburn, J, Collins, C, Cooper, A, Covele, B, Crippen, J, Crocker, N, Crowley, B, Dal Molin, A, Davis, E, Degrassie, J, del-Castillo-Negrete, C, Delgado-Aparicio, L, Diallo, A, Diem, S, Ding, R, Ding, S, Ding, W, Doane, J, Donovan, D, Drake, J, Du, D, Du, H, Du, X, Duarte, V, Duran, J, Eidietis, N, Elder, D, Eldon, D, Elwasif, W, Ely, T, Eng, K, Engelhorn, K, Ennis, D, Erickson, K, Ernst, D, Evans, T, Fenstermacher, M, Ferraro, N, Ferron, J, Finkenthal, D, Fisher, P, Fishler, B, Flanagan, S, Fooks, J, Frassinetti, L, Frerichs, H, Fu, Y, Fulop, T, Gao, Q, Garcia, F, Garofalo, A, Gattuso, A, Giacomelli, L, Giraldez, E, Giroud, C, Glass, F, Gohil, P, Gong, X, Gorelov, Y, Granetz, R, Green, D, Greenfield, C, Grierson, B, Groebner, R, Grosnickle, W, Groth, M, Grunloh, H, Guo, H, Guo, W, Guterl, J, Hager, R, Hahn, S, Halpern, F, Han, H, Hansink, M, Hanson, J, Harris, J, Haskey, S, Hatch, D, Heidbrink, W, Herfindal, J, Hill, D, Hill, M, Hinson, E, Holcomb, C, Holland, C, Holland, L, Hollmann, E, Holm, A, Hong, R, Hoppe, M, Houshmandyar, S, Howard, J, Howard, N, Hu, Q, Hu, W, Huang, H, Huang, J, Huang, Y, Hughes, G, Hughes, J, Humphreys, D, Hyatt, A, Ida, K, Igochine, V, In, Y, Inoue, S, Isayama, A, Isler, R, Izzo, V, Jackson, M, Jarvinen, A, Jeon, Y, Ji, H, Jian, X, Jimenez, R, Johnson, C, Joseph, I, Kaczala, D, Kaplan, D, Kates-Harbeck, J, Kellman, A, Kellman, D, Kessel, C, Khumthong, K, Kim, C, Kim, H, Kim, J, Kim, K, Kim, S, Kimura, W, King, J, Kirk, A, Kleijwegt, K, Knolker, M, Kohn, A, Kolemen, E, Kostuk, M, Kramer, G, Kress, P, Kriete, D, La Haye, R, Laggner, F, Lan, H, Lanctot, M, Lantsov, R, Lao, L, Lasnier, C, Lau, C, Law, K, Lawrence, D, Le, J, Lee, R, Lehnen, M, Leon, R, Leonard, A, Lesher, M, Leuer, J, Li, G, Li, K, Liao, K, Lin, Z, Liu, C, Liu, F, Liu, Y, Liu, Z, Loch, S, Logan, N, Lohr, J, Lore, J, Luce, T, Luhmann, N, Lunsford, R, Luo, C, Luo, Z, Lupin-Jimenez, L, Lvovskiy, A, Lyons, B, Ma, X, Maingi, R, Makowski, M, Mantica, P, Manuel, M, Margo, M, Marinoni, A, Marmar, E, Martin, W, Masline, R, Matsunaga, G, Mauzey, D, Mauzey, P, Mcclenaghan, J, Mckee, G, Mclean, A, Mclean, H, Meier, E, Meitner, S, Menard, J, Meneghini, O, Merlo, G, Meyer, W, Miller, D, Miller, W, Moeller, C, Montes, K, Morales, M, Mordijck, S, Moser, A, Moyer, R, Muller, S, Munaretto, S, Murakami, M, Murphy, C, Muscatello, C, Myers, C, Nagy, A, Navratil, G, Nazikian, R, Neff, A, Neiser, T, Nelson, A, Nguyen, P, Nguyen, R, Nichols, J, Nocente, M, Nygren, R, O'Neill, R, Odstrcil, T, Ohdachi, S, Okabayashi, M, Olofsson, E, Ono, M, Orlov, D, Osborne, T, Pablant, N, Pace, D, Paguio, R, Pajares Martinez, A, Pan, C, Pankin, A, Park, J, Park, Y, Parker, C, Parker, S, Parks, P, Pawley, C, Paz-Soldan, C, Peebles, W, Penaflor, B, Petrie, T, Petty, C, Peysson, Y, Pigarov, A, Piglowski, D, Pinsker, R, Piovesan, P, Piper, N, Pitts, R, Pizzo, J, Podesta, M, Poli, F, Ponce, D, Porkolab, M, Porter, G, Prater, R, Qian, J, Ra, O, Rafiq, T, Raman, R, Rand, C, Randall, G, Rauch, J, Rea, C, Reinke, M, Ren, J, Ren, Q, Ren, Y, Rhodes, T, Rice, J, Rognlien, T, Rost, J, Rowan, W, Rudakov, D, Salmi, A, Sammuli, B, Samuell, C, Sandorfi, A, Sang, C, Sauter, O, Schissel, D, Schmitz, L, Schmitz, O, Schuster, E, Scoville, J, Seltzman, A, Sfiligoi, I, Shafer, M, Shen, H, Shi, T, Shiraki, D, Si, H, Smith, D, Smith, S, Snipes, J, Snyder, P, Solano, E, Solomon, W, Sontag, A, Soukhanovskii, V, Spong, D, Stacey, W, Staebler, G, Stagner, L, Stahl, B, Stangeby, P, Stoltzfus-Dueck, T, Stotler, D, Strait, E, Su, D, Sugiyama, L, Sulyman, A, Sun, Y, Sung, C, Suttrop, W, Suzuki, Y, Svyatkovskiy, A, Sweeney, R, Taimourzadeh, S, Takechi, M, Tala, T, Tan, H, Tang, S, Tang, X, Taussig, D, Taylor, G, Taylor, N, Taylor, T, Teklu, A, Thomas, D, Thomas, M, Thome, K, Thorman, A, Tinguely, R, Tobias, B, Tooker, J, Torreblanca, H, Torrezan De Sousa, A, Trevisan, G, Truong, D, Turco, F, Turnbull, A, Unterberg, E, Vaezi, P, Vail, P, Van Zeeland, M, Velasco Enriquez, M, Venkatesh, M, Victor, B, Volpe, F, Wade, M, Walker, M, Wall, J, Wallace, G, Waltz, R, Wang, G, Wang, H, Wang, Y, Wang, Z, Wang, F, Ward, S, Watkins, J, Watkins, M, Wehner, W, Weiland, M, Weisberg, D, Welander, A, White, A, White, R, Whyte, D, Wijkamp, T, Wilcox, R, Wilks, T, Wilson, H, Wingen, A, Wolfe, E, Wu, M, Wu, W, Wukitch, S, Xia, T, Xiang, N, Xiao, B, Xie, R, Xu, G, Xu, H, Xu, X, Yan, Z, Yang, Q, Yang, X, Yoshida, M, Yu, G, Yu, J, Yu, M, Zamperini, S, Zeng, L, Zhao, B, Zhao, D, Zhao, H, Zhao, Y, Zhu, Y, and Zywicki, B
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Physics ,Nuclear and High Energy Physics ,fusion ,model ,Tokamak ,DIII-D ,Divertor ,Mechanics ,Plasma ,Fusion power ,Dissipation ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Pedestal ,Heat flux ,law ,Physics::Plasma Physics ,0103 physical sciences ,010306 general physics ,tokamak ,plasma ,energy - Abstract
DIII-D research is addressing critical challenges in preparation for ITER and the next generation of fusion devices through focusing on plasma physics fundamentals that underpin key fusion goals, understanding the interaction of disparate core and boundary plasma physics, and developing integrated scenarios for achieving high performance fusion regimes. Fundamental investigations into fusion energy science find that anomalous dissipation of runaway electrons (RE) that arise following a disruption is likely due to interactions with RE-driven kinetic instabilities, some of which have been directly observed, opening a new avenue for RE energy dissipation using naturally excited waves. Dimensionless parameter scaling of intrinsic rotation and gyrokinetic simulations give a predicted ITER rotation profile with significant turbulence stabilization. Coherence imaging spectroscopy confirms near sonic flow throughout the divertor towards the target, which may account for the convection-dominated parallel heat flux. Core-boundary integration studies show that the small angle slot divertor achieves detachment at lower density and extends plasma cooling across the divertor target plate, which is essential for controlling heat flux and erosion. The Super H-mode regime has been extended to high plasma current (2.0 MA) and density to achieve very high pedestal pressures (~30 kPa) and stored energy (3.2 MJ) with H 98y2 ≈ 1.6–2.4. In scenario work, the ITER baseline Q = 10 scenario with zero injected torque is found to have a fusion gain metric independent of current between q 95 = 2.8–3.7, and a lower limit of pedestal rotation for RMP ELM suppression has been found. In the wide pedestal QH-mode regime that exhibits improved performance and no ELMs, the start-up counter torque has been eliminated so that the entire discharge uses ≈0 injected torque and the operating space is more ITER-relevant. Finally, the high- (⩽3.8) hybrid scenario has been extended to the high-density levels necessary for radiating divertor operation, achieving ~40% divertor heat flux reduction using either argon or neon with P tot up to 15 MW.
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- 2019
4. Impact of resonant magnetic perturbations on zonal flows and microturbulence
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T. Nishizawa, D. M. Kriete, Z. R. Williams, M.J. Pueschel, J. S. Sarff, Paul Terry, S. H. Nogami, G. R. McKee, Mark Nornberg, and D. M. Orlov
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Physics ,Nuclear and High Energy Physics ,Tokamak ,Turbulence ,law ,Quantum electrodynamics ,Microturbulence ,Condensed Matter Physics ,Resonant magnetic perturbations ,law.invention - Published
- 2020
5. Review of pulsed power-driven high energy density physics research on Z at Sandia
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Raymond C. Clay, Brian Hutsel, P. W. Lake, Steve MacLaren, J. A. Fisher, Bernardo Farfan, S. Beatty, Ian C. Smith, James E. Bailey, J. S. Custer, R. B. Campbell, Marius Schollmeier, H. T. Barclay, Joshua J. Leckbee, Mark Kimmel, Dale Welch, J. R. Fein, Kelly Hahn, Gordon A. Chandler, Gregory Rochau, William Lewis, Michael A. Mangan, Jens Schwarz, Justin Brown, Kris Beckwith, Dawn G. Flicker, Kumar Raman, Nathan W. Moore, William D. Reinhart, Quinn Looker, Thomas A. Haill, M. J. Speir, Carlos L. Ruiz, J. D. Douglass, M. A. Schaeuble, Seth Root, J. F. Benage, M. Wu, G. Loisel, P. J. Christenson, Jack LeRoy Wise, Maurice Keith Matzen, D. J. Lucero, M. D. Mitchell, Evstati Evstatiev, Michael G. Mazarakis, P. T. Springer, Ella Suzanne Field, E. A. Weinbrecht, Clayton E. Myers, C. Aragon, C. Highstrete, P. A. Jones, C. A. McCoy, Paul Schmit, S. G. Patel, T. Gomez, S. Radovich, William A. Stygar, Ryan D. McBride, M. E. Cuneo, John P. Apruzese, John Giuliani, Timothy D. Pointon, Arati Dasgupta, Eric Harding, N. D. Hamlin, Matthias Geissel, Jonathon Shores, Kyle Robert Cochrane, M. R. Gomez, D. Spencer, John Lee McKenney, C. R. Ball, Mark Herrmann, Thomas James Awe, Patrick Knapp, J. W. Kellogg, Sakun Duwal, Christopher Jennings, A. J. Lopez, Marcus D. Knudson, R. J. Kamm, J. Ward Thornhill, Patrick K. Rambo, G. R. McKee, Christine Anne Coverdale, E.M. Campbell, Timothy McGuire Flanagan, P. Kalita, Michael P. Desjarlais, M. H. Hess, P. Gard, Kevin Baker, J.-P. Davis, Roger Alan Vesey, Tommy Ao, Thomas R. Mattsson, G. A. Shipley, A. Kreft, Raymond W. Lemke, G. S. Dunham, David Yager-Elorriaga, Matthew Martin, G. Natoni, R. J. Leeper, Brian Stoltzfus, D. J. Ampleford, Aaron Edens, C. Tyler, P. E. Wakeland, Taisuke Nagayama, Drew Johnson, E. B. Christner, Rudolph J. Magyar, G. T. Leifeste, Timothy J. Webb, D. Sandoval, D. V. Rose, M. C. Jones, D. Headley, Andrew Baczewski, Derek C. Lamppa, Sean Simpson, Adam B Sefkow, Kevin N. Austin, B. A. Branch, P. E. Specht, Kyle Peterson, Daniel Sinars, George Laity, M. D. Christison, Harry McLean, A. M. Steiner, M. D. Furnish, S. A. Lewis, A. J. Harvey-Thompson, Benjamin R. Galloway, Edmund Yu, W. L. Langston, K. Chandler, D. G. Chacon, A. R. Miles, C. S. Alexander, M. J. Edwards, A. Yu, Christopher Jay Bourdon, M. R. Weis, J. H. Hammer, Brent Manley Jones, B. M. Cook, Luke Shulenburger, J. A. Mills, S. A. Slutz, Anthony P. Colombo, A. J. Maurer, Karen Blaha, Gary Grim, Kate Bell, C. S. Speas, Christopher T Seagle, Nichelle Bennett, John L. Porter, Daniel H. Dolan, H. L. Hanshaw, M. A. Sweeney, T. A. Gardiner, J. J. Boerner, David B. Seidel, M. E. Sceiford, Jose A. Torres, Stephanie Hansen, Mark E. Savage, Daniel Ruiz, Andrew Porwitzky, D. J. Armstrong, O. Johns, A. C. Owen, Mark D. Johnston, Omar Hurricane, J. S. Lash, K. R. LeChien, David E. Bliss, Michael E. Glinsky, Joshua P. Townsend, Dean C. Rovang, G. K. Robertson, and Mark L. Kiefer
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Physics ,Nuclear engineering ,Electric potential energy ,Plasma ,Pulsed power ,Radiation ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Capacitor ,law ,0103 physical sciences ,Current (fluid) ,010306 general physics ,Inertial confinement fusion ,Energy (signal processing) - Abstract
Pulsed power accelerators compress electrical energy in space and time to provide versatile experimental platforms for high energy density and inertial confinement fusion science. The 80-TW “Z” pulsed power facility at Sandia National Laboratories is the largest pulsed power device in the world today. Z discharges up to 22 MJ of energy stored in its capacitor banks into a current pulse that rises in 100 ns and peaks at a current as high as 30 MA in low-inductance cylindrical targets. Considerable progress has been made over the past 15 years in the use of pulsed power as a precision scientific tool. This paper reviews developments at Sandia in inertial confinement fusion, dynamic materials science, x-ray radiation science, and pulsed power engineering, with an emphasis on progress since a previous review of research on Z in Physics of Plasmas in 2005.
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- 2020
6. Magnetically Driven Implosions for Inertial Confinement Fusion at Sandia National Laboratories
- Author
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Brent Manley Jones, Stephanie Hansen, Gregory Rochau, M. E. Cuneo, S. A. Slutz, S. E. Rosenthal, Raymond W. Lemke, Mark Herrmann, Michael G. Mazarakis, Carlos L. Ruiz, Roger Alan Vesey, Eric Harding, A. J. Harvey-Thompson, G. R. McKee, R. J. Leeper, Charles Nakhleh, Edmund Yu, D. J. Ampleford, Michael Jones, M. R. Lopez, Albert Carter Owen, P. J. Christenson, John L. Porter, Gary Wayne Cooper, G. T. Leifeste, Kelly Hahn, Gordon A. Chandler, M. A. Sweeney, Christopher Jennings, Briggs W. Atherton, Daniel Sinars, John Lee McKenney, L. A. McPherson, Derek C. Lamppa, Dean C. Rovang, R. J. Kaye, A. J. Lopez, P. K. Rambo, William A. Stygar, Mark E. Savage, Kyle Peterson, Ryan D. McBride, Ian C. Smith, James E. Bailey, M. H. Hess, Eduardo Waisman, Matthew R. Gomez, Patrick Knapp, M. K. Matzen, Matthew Martin, Thomas James Awe, and Adam B Sefkow
- Subjects
Nuclear physics ,Physics ,Nuclear and High Energy Physics ,Magnetic energy ,Z-pinch ,Nuclear engineering ,Magnetized Liner Inertial Fusion ,Magnetized target fusion ,Magnetic pressure ,Pulsed power ,Fusion power ,Condensed Matter Physics ,Inertial confinement fusion - Abstract
High current pulsed-power generators efficiently store and deliver magnetic energy to z-pinch targets. We review applications of magnetically driven implosions (MDIs) to inertial confinement fusion. Previous research on MDIs of wire-array z-pinches for radiation-driven indirect-drive target designs is summarized. Indirect-drive designs are compared with new targets that are imploded by direct application of magnetic pressure produced by the pulsed-power current pulse. We describe target design elements such as larger absorbed energy, magnetized and pre-heated fuel, and cryogenic fuel layers that may relax fusion requirements. These elements are embodied in the magnetized liner inertial fusion (MagLIF) concept [Slutz “Pulsed-power-driven cylindrical liner implosions of laser pre-heated fuel magnetized with an axial field,” Phys. Plasmas, 17, 056303 (2010), and Stephen A. Slutz and Roger A. Vesey, “High-Gain Magnetized Inertial Fusion,” Phys. Rev. Lett., 108, 025003 (2012)]. MagLIF is in the class of magneto-inertial fusion targets. In MagLIF, the large drive currents produce an azimuthal magnetic field that compresses cylindrical liners containing pre-heated and axially pre-magnetized fusion fuel. Scientific breakeven may be achievable on the Z facility with this concept. Simulations of MagLIF with deuterium-tritium fuel indicate that the fusion energy yield can exceed the energy invested in heating the fuel at a peak drive current of about 27 MA. Scientific breakeven does not require alpha particle self-heating and is therefore not equivalent to ignition. Capabilities to perform these experiments will be developed on Z starting in 2013. These simulations and predictions must be validated against a series of experiments over the next five years. Near-term experiments are planned at drive currents of 16 MA with D2 fuel. MagLIF increases the efficiency of coupling energy (=target absorbed energy/driver stored energy) to targets by 10-150X relative to indirect-drive targets. MagLIF also increases the absolute energy absorbed by the target by 10-50X relative to indirect-drive targets. These increases could lead to higher fusion gains and yields. Single-shot high yields are of great utility to national security missions. Higher efficiency and higher gains may also translate into more compelling (lower cost and complexity) fusion reactor designs. We will discuss the broad goals of the emerging research on the MagLIF concept and identify some of the challenges. We will also summarize advances in pulsed-power technology and pulsed-power driver architectures that double the efficiency of the driver.
- Published
- 2012
7. Progress on advanced tokamak and steady-state scenario development on DIII-D and NSTX
- Author
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E J Doyle, A M Garofalo, C M Greenfield, S M Kaye, J E Menard, M Murakami, S A Sabbagh, M E Austin, R E Bell, K H Burrell, J R Ferron, D A Gates, R J Groebner, A W Hyatt, R J Jayakumar, J E Kinsey, B P LeBlanc, T C Luce, G R McKee, M Okabayashi, Y-K M Peng, C C Petty, P A Politzer, T L Rhodes, M R Wade, R E Waltz, the DIII-D, and NSTX Research Teams
- Subjects
Physics ,Tokamak ,Steady state ,DIII-D ,Magnetic confinement fusion ,Plasma ,Zonal flow (plasma) ,Condensed Matter Physics ,law.invention ,Bootstrap current ,Nuclear physics ,Nuclear Energy and Engineering ,law ,Beta (plasma physics) - Abstract
Advanced tokamak (AT) research seeks to develop steady-state operating scenarios for ITER and other future devices from a demonstrated scientific basis. Normalized target parameters for steady-state operation on ITER are 100% non-inductive current operation with a bootstrap current fraction f BS ≥ 60%, q 95 ∼ 4-5 and G ≡ β N H scaling /q 2 95 ≥ 0.3. Progress in realizing such plasmas is considered in terms of the development of plasma control capabilities and scientific understanding, leading to improved AT performance. NSTX has demonstrated active resistive wall mode stabilization with low, ITER-relevant, rotation rates below the critical value required for passive stabilization. On DIII-D, experimental observations and GYRO simulations indicate that ion internal transport barrier (ITB) formation at rational-q surfaces is due to equilibrium zonal flows generating high local E x B shear levels. In addition, stability modelling for DIII-D indicates a path to operation at β N ≥ 4 with q min ≥ 2, using broad, hollow current profiles to increase the ideal wall stability limit. Both NSTX and DIII-D have optimized plasma performance and expanded AT operational limits. NSTX now has long-pulse, high performance discharges meeting the normalized targets for an spherical torus-based component test facility. DIII-D has developed sustained discharges combining high beta and ITBs, with performance approaching levels required for AT reactor concepts, e.g. β N = 4, H 89 = 2.5, with f BS > 60%. Most importantly, DIII-D has developed ITER steady-state demonstration discharges, simultaneously meeting the targets for steady-state Q ≥ 5 operation on ITER set out above, substantially increasing confidence in ITER meeting its steady-state performance objective.
- Published
- 2006
8. Observation and characterization of radially sheared zonal flows in DIII-D
- Author
-
G. R. McKee, Xueqiao Xu, Dmitry Rudakov, M. W. Jakubowski, R. J. Fonck, Klaus Hallatschek, R.A. Moyer, W. Nevins, and Keith H. Burrell
- Subjects
Physics ,DIII-D ,Turbulence ,K-epsilon turbulence model ,Magnetic confinement fusion ,Plasma ,Condensed Matter Physics ,Computational physics ,Physics::Fluid Dynamics ,Wavelength ,Classical mechanics ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,Physics::Space Physics ,Plasma diagnostics ,Shear flow - Abstract
Zonal flows, thought crucial to the saturation and self-regulation of turbulence and turbulent transport in magnetically confined plasmas, have been observed and characterized in the edge region of DIII-D plasmas. These flows exhibit temperature scaling characteristics and spatial features predicted for geodesic acoustic modes (GAMs), a class of higher-frequency zonal flows seen in nonlinear simulations of plasma turbulence. The zonal flows (GAMs) have been observed in the turbulence flow-field in the radial region 0.85 ≤ r/a ≤ 1.0 via application of time-delay-estimation techniques to two-dimensional measurements of density fluctuations, obtained with beam emission spectroscopy. Spatial and temporal analysis of the resulting flow-field demonstrates the existence of a coherent oscillation (approximately 15 kHz) in the poloidal flow of density fluctuations that has a long poloidal wavelength, possibly m = 0, narrow radial extent (krρi < 0.2), and a frequency that varies monotonically with the local temperature. The approximate effective shearing rate, dvθ/d r, of the flow is of the same order of magnitude as the measured nonlinear decorrelation rate of the turbulence. These characteristics are consistent with predicted features of zonal flows, specifically identified as GAMs, observed in three-dimensional Braginskii simulations of core/edge turbulence.
- Published
- 2003
9. Experimental characterization of coherent, radially-sheared zonal flows in the DIII-D tokamak
- Author
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R. J. Fonck, Klaus Hallatschek, Dmitry Rudakov, R.A. Moyer, G.D. Porter, Paul Schoch, Xueqiao Xu, Keith H. Burrell, William M. Nevins, M. W. Jakubowski, and G. R. McKee
- Subjects
Physics ,Tokamak ,DIII-D ,Turbulence ,Oscillation ,Reynolds stress ,Condensed Matter Physics ,law.invention ,Computational physics ,Physics::Fluid Dynamics ,Wavelength ,Amplitude ,Classical mechanics ,Physics::Plasma Physics ,law ,Wavenumber - Abstract
A271 EXPERIMENTAL CHARACTERIZATION OF COHERENT, RADIALLY-SHEARED ZONAL FLOWS IN THE DIII-D TOKAMAK. Application of time-delay-estimation techniques to two-dimensional measurements of density fluctuations, obtained with beam emission spectroscopy in DIII-D plasmas, has provided temporally and spatially resolved measurements of the turbulence flow-field. Features that are characteristic of self-generated zonal flows are observed in the radial region near 0.85 {
- Published
- 2003
10. Comparison of turbulence measurements from DIII-D low-mode and high-performance plasmas to turbulence simulations and models
- Author
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G. Wang, Lei Zeng, Richard Sydora, J. N. Leboeuf, W. A. Peebles, T. L. Rhodes, Curtis L. Rettig, G. R. McKee, R. J. Groebner, and E. J. Doyle
- Subjects
Physics ,Tokamak ,DIII-D ,Turbulence ,law ,Gyroradius ,Nuclear fusion ,Plasma ,Radius ,Atomic physics ,Condensed Matter Physics ,law.invention ,Ion - Abstract
Measured turbulence characteristics (correlation lengths, spectra, etc.) in low-confinement (L-mode) and high-performance plasmas in the DIII-D tokamak [Luxon et al., Proceedings Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] show many similarities with the characteristics determined from turbulence simulations. Radial correlation lengths Δr of density fluctuations from L-mode discharges are found to be numerically similar to the ion poloidal gyroradius ρθ,s, or 5–10 times the ion gyroradius ρs over the radial region 0.2
- Published
- 2002
11. Characterization of avalanche-like events in a confined plasma
- Author
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T.L. Rhodes, C. X. Yu, E. J. Doyle, M. Gilmore, R. A. Moyere, P. A. Politzer, Max E Austin, Todd Evans, and G. R. McKee
- Subjects
Hurst exponent ,Physics ,Condensed matter physics ,Heat flux ,Turbulence ,Wave turbulence ,Electron temperature ,Radius ,Plasma ,Condensed Matter Physics ,Scaling ,Computational physics - Abstract
One mechanism for transport of energy and particles in a plasma is by discrete, intermittent, uncorrelated events, often called avalanches. This paper reports observations and quantitative characterization of avalanche events in a magnetically confined plasma. The observations are primarily of electron temperature fluctuations. Avalanches are identified by their large spatial scale, up to the system size, by self-similar behavior in the frequency spectrum and the autocorrelation function and by propagation. The two-point cross-correlation function allows determination of a characteristic velocity, which typically varies from several hundred meters per second in the outer part of the plasma to zero or even inward near the axis. This can be interpreted as resulting from the prevalence of negative avalanches (i.e., holes) near the axis. The presence of a long-tailed probability distribution is indicated by a Hurst parameter (H) in the range 0.80 to 0.95, which becomes smaller in the outer quarter of the plasma radius. Density fluctuation spectra from the plasma core also show self-similar behavior. Power transport estimates show that about half of the heat flux is carried by the avalanche events under conditions with no magnetohydrodynamic activity. These observations are qualitatively similar to results of modeling calculations based on drift wave turbulence. It is reasonable to infer that avalanches are the macroscopic manifestation of turbulence which inherently has a small spatial scale and, thus, allow a local, gyro-Bohm scaling process to show global Bohm-type behavior.
- Published
- 2002
12. The quiescent double barrier regime in DIII-D
- Author
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C M Greenfield, K H Burrell, E J Doyle, R J Groebner, W P West, T A Casper, J C DeBoo, C Fenzi, P Gohil, J E Kinsey, L L Lao, J N Leboeuf, M A Makowski, G R McKee, R A Moyer, M Murakami, R I Pinsker, G D Porter, C L Rettig, T L Rhodes, G M Staebler, B W Stallard, E J Synakowski, L Zeng, and the DIII-D Team
- Subjects
Materials science ,Tokamak ,DIII-D ,business.industry ,Turbulence ,Pulse duration ,Cryopump ,Condensed Matter Physics ,Molecular physics ,Bootstrap current ,law.invention ,Optics ,Nuclear Energy and Engineering ,law ,Beta (plasma physics) ,Magnetohydrodynamics ,business - Abstract
The quiescent double barrier (QDB) regime is a high performance regime recently identified in DIII-D and characterized by a double transport barrier structure (core and edge) that can be maintained for several seconds, often limited only by the pulse length capabilities of the DIII-D hardware. The QDB regime has been sustained for up to 25 τE with fusion performance of up to βNH89≈7. The edge barrier is ELM-free, but modulated by low frequency MHD activity that allows density control via an external cryopump. The core barrier is similar to those seen in previous internal transport barrier experiments, but is maintained without complete stabilization of turbulence. Instead, the turbulence correlation lengths become very short so as to minimize the transport length scales. The two barriers are separated by a region of high transport that is a consequence of a zero-crossing in the E×B shearing rate. These discharges typically possess highly peaked density profiles. This has several implications: narrow bootstrap current profile, reduced beta limit and increased impurity retention. We will report on studies of each of these issues.
- Published
- 2002
13. Transport by intermittent convection in the boundary of the DIII-D tokamak
- Author
-
S.L. Allen, P.C. Stangeby, Dmitry Rudakov, R.A. Moyer, Jose Boedo, P. West, M. Tillack, R. J. Fonck, Todd Evans, G. R. McKee, G. D. Porter, A. Mahdavi, Anthony Leonard, Sergei Krasheninnikov, M.J. Schaffer, G. Antar, Dennis Whyte, E. M. Hollmann, and George Tynan
- Subjects
Physics ,Convection ,Amplitude ,Tokamak ,DIII-D ,law ,Electric field ,Flux ,Plasma diagnostics ,Plasma ,Atomic physics ,Condensed Matter Physics ,law.invention - Abstract
Intermittent plasma objects (IPOs) featuring higher pressure than the surrounding plasma, and responsible for ∼50% of the E×BT radial transport, are observed in the scrape off layer (SOL) and edge of the DIII-D tokamak [J. Watkins et al., Rev. Sci. Instrum. 63, 4728 (1992)]. Conditional averaging reveals that the IPOs, produced at a rate of ∼3×103 s−1, are positively charged and also polarized, featuring poloidal electric fields of up to 4000 V/m. The IPOs move poloidally at speeds of up to 5000 m/s and radially with E×BT/B2 velocities of ∼2600 m/s near the last closed flux surface (LCFS), and ∼330 m/s near the wall. The IPOs slow down as they shrink in radial size from 4 cm at the LCFS to 0.5 cm near the wall. The IPOs appear in the SOL of both L and H mode discharges and are responsible for nearly 50% of the SOL radial E×B transport at all radii; however, they are highly reduced in absolute amplitude in H-mode conditions.
- Published
- 2001
14. Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak
- Author
-
Ch. Fuchs, M. A. Makowski, Dylan Brennan, T.C. Luce, C. M. Greenfield, M. R. Wade, J.G. Watkins, T. L. Rhodes, Curtis L. Rettig, Max E Austin, Cc Petty, P. Gohil, L. L. Lao, E. J. Synakowski, J.C. Rost, E. J. Strait, E. J. Doyle, G. R. McKee, W.P. West, R.A. Moyer, Keith H. Burrell, B. W. Stallard, C. Fenzi, R. J. Groebner, J.C. DeBoo, and Miklos Porkolab
- Subjects
Nuclear physics ,High-confinement mode ,Physics ,Tokamak ,DIII-D ,law ,Divertor ,Beta (plasma physics) ,Nuclear fusion ,Plasma ,Condensed Matter Physics ,Double barrier ,law.invention - Abstract
High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation that is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 s or >25 en...
- Published
- 2001
15. Understanding and control of transport in Advanced Tokamak regimes in DIII-D
- Author
-
T. L. Rhodes, Curtis L. Rettig, R. J. Groebner, J.C. DeBoo, Larry R. Baylor, J.R. Ferron, M. A. Makowski, R. Prater, P. Gohil, E. J. Synakowski, E. J. Strait, Daniel Thomas, T.A. Casper, E. J. Doyle, M. R. Wade, G. M. Staebler, K. H. Burrell, D.R. Ernst, T.C. Luce, R. I. Pinsker, L.L. Lao, C.C. Petty, G. L. Schmidt, C. M. Greenfield, Masakatsu Murakami, B. W. Stallard, P.A. Politzer, B. W. Rice, and G. R. McKee
- Subjects
Physics ,Tokamak ,DIII-D ,Magnetic confinement fusion ,Plasma ,Condensed Matter Physics ,Neutral beam injection ,law.invention ,High-confinement mode ,Nuclear physics ,law ,Nuclear fusion ,Atomic physics ,Transport phenomena - Abstract
Transport phenomena are studied in Advanced Tokamak (AT) regimes in the DIII-D tokamak [Plasma Physics and Controlled Nuclear Fusion Research, 1986 (International Atomics Energy Agency, Vienna, 1987), Vol. I, p. 159], with the goal of developing understanding and control during each of three phases: Formation of the internal transport barrier (ITB) with counter neutral beam injection taking place when the heating power exceeds a threshold value of about 9 MW, contrasting to co-NBI injection, where Pthreshold
- Published
- 2000
16. Divertor plasma studies on DIII-D: experiment and modelling
- Author
-
M.J. Schaffer, Anthony Leonard, N.H. Brooks, D. G. Nilson, A.W. Hyatt, Charles Lasnier, M. R. Wade, R. D. Wood, J.G. Watkins, G.D. Porter, S. Tugarinov, W.H. Meyer, T.W. Petrie, D. N. Hill, M.A. Mahdavi, Dean A. Buchenauer, Daniel Thomas, R.D. Stambaugh, Terry Rhodes, R.A. Jong, G. R. McKee, S.L. Allen, W. P. West, E. J. Doyle, R.A. Moyer, C. Christopher Klepper, G.L. Jackson, J.W. Cuthbertson, T. N. Carlstrom, R.C. Isler, Todd Evans, Max E. Fenstermacher, Rajesh Maingi, and Dennis Whyte
- Subjects
Materials science ,Tokamak ,DIII-D ,Divertor ,Plasma ,Mechanics ,Radiation ,Condensed Matter Physics ,law.invention ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,Impurity ,law ,Physics::Space Physics ,Radiative transfer ,Plasma diagnostics ,Atomic physics - Abstract
In a magnetically diverted tokamak, the scrape-off layer (SOL) and divertor plasma separates the first wall from the core plasma, intercepting impurities generated at the wall before they reach the core plasma. The divertor plasma can also serve to spread the heat and particle flux over a large area of divertor structure wall using impurity radiation and neutral charge exchange, thus reducing peak heat and particle fluxes at the divertor strike plate. Such a reduction will be required in the next generation of tokamaks, for without it the divertor engineering requirements are very demanding. To successfully demonstrate a radiative divertor, a highly radiative condition with significant volume recombination must be achieved in the divertor, while maintaining a low impurity content in the core plasma. Divertor plasma properties are determined by a complex interaction of classical parallel transport, anomalous perpendicular transport, impurity transport and radiation, and plasma - wall interaction. In this paper we will describe a set of experiments on DIII-D designed to provide detailed two-dimensional documentation of the divertor and SOL plasma. Measurements have been made in operating modes where the plasma is attached to the divertor strike plate and in highly radiating cases where the plasma is detached from the divertor strike plate. We will also discuss the results of experiments designed to influence the distribution of impurities in the plasma using enhanced SOL plasma flow. Extensive modelling efforts will be described which are successfully reproducing attached plasma conditions and are helping to elucidate the important plasma and atomic physics involved in the detachment process.
- Published
- 1997
17. Transport measurements for confined non-thermal alpha particles in TFTR DT plasmas
- Author
-
A. T. Ramsey, R.J. Fonck, R.V. Budny, B. C. Stratton, Z. Chang, and G. R. McKee
- Subjects
Nuclear and High Energy Physics ,Range (particle radiation) ,Materials science ,Anomalous diffusion ,Bremsstrahlung ,Radius ,Alpha particle ,Plasma ,Diffusion (business) ,Atomic physics ,Condensed Matter Physics ,Tokamak Fusion Test Reactor - Abstract
Fusion produced non-thermal alpha particle radial profile measurements are obtained with the α-CHERS diagnostic in deuterium-tritium (DT) supershot plasmas on the Tokamak Fusion Test Reactor (TFTR). Alpha particles in the energy range 0.15 ≤ Eα ≤ 0.6 MeV are observed spectroscopically over a five point radial profile. The extracted non-thermal alpha signal is ≤ 1% of the background bremsstrahlung intensity for typical total fast alpha densities in the range (0.5-1.0) × 1017 m-3. The profiles obtained in two sets of discharges vary slightly, and are best described by a slowing down alpha distribution subject to neoclassical diffusion plus a small anomalous cross-field diffusion. The data are consistent with an effective anomalous diffusion coefficient in the range 0.00 ≤ Dα,a ≤ 0.10 m2/s, where Dα ,a is constant with alpha energy and with radius
- Published
- 1997
18. Observation of sawtooth redistribution of non-thermal, confined alpha particles in TFTR DT discharges
- Author
-
Z. Chang, B. C. Stratton, F. Wising, R.V. Budny, G. R. McKee, R.J. Ponck, and A. Ödblom
- Subjects
Nuclear and High Energy Physics ,Materials science ,Distribution function ,Physics::Plasma Physics ,Drop (liquid) ,Thermal ,Plasma diagnostics ,Redistribution (chemistry) ,Plasma ,Sawtooth wave ,Alpha particle ,Atomic physics ,Condensed Matter Physics - Abstract
Radial profiles of the density of confined alpha particles with energies in the 0.15 to 0.6 MeV range are spectroscopically observed before and after a sawtooth crash in a TFTR deuterium-tritium plasma. A large drop in the core alpha density is seen, indicating expulsion of alphas from the core to the plasma periphery. The measured changes in the alpha density profiles are consistent with predictions based on the Kolesnichenko sawtooth model in this case
- Published
- 1996
19. Spectroscopic observation of 0-300 keV3He ions produced by ICRF heating in TFTR
- Author
-
Gregory W. Hammett, G. R. McKee, B. C. Stratton, C. K. Phillips, R.J. Fonck, T. Thorson, and E. J. Synakowski
- Subjects
Nuclear and High Energy Physics ,Materials science ,Alpha particle ,Condensed Matter Physics ,Ion ,Nuclear physics ,Physics::Plasma Physics ,Helium-3 ,Thermal ,Nuclear fusion ,Plasma diagnostics ,Emission spectrum ,Atomic physics ,Tokamak Fusion Test Reactor - Abstract
Helium-3 ions with energies from thermal values up to 300 keV produced by ICRF heating have been spectroscopically observed by the α-CHERS diagnostic on the Tokamak Fusion Test Reactor (TFTR). The shape of the spectrum and the temporal and spatial behaviour of the energetic 3He ion emission are consistent with expectations for this ICRF heating case. Because the 3He ion density was similar to the alpha particle density predicted for D-T supershots on TFTR, these observations give confidence that confined alphas produced by D-T fusion reactions can be observed by α-CHERS during D-T operation of TFTR
- Published
- 1994
20. Characterization of off-axis fishbones
- Author
-
W. M. Solomon, Y. B. Zhu, D. C. Pace, M. Garcia-Munoz, E. J. Strait, G. R. McKee, M. E. Austin, R. K. Fisher, M. Okabayashi, G. Matsunaga, K. Shinohara, Christopher Muscatello, W. W. Heidbrink, M. A. Van Zeeland, R. A. Moyer, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, and Universidad de Sevilla. RNM138: Física Nuclear Aplicada
- Subjects
Larmor precession ,Physics ,Toroid ,Tokamak ,business.industry ,Phase (waves) ,Condensed Matter Physics ,Rotation ,law.invention ,Optics ,Amplitude ,Nuclear Energy and Engineering ,law ,Physics::Plasma Physics ,Harmonics ,Chirp ,Atomic physics ,business - Abstract
Repetitive bursting instabilities with strong frequency chirping occur in highbeta, beam-heated plasmas with safety factor q > 1 in the DIII-D tokamak. Although the mode structures differ, in many ways, the off-axis fishbones are similar to the q = 1 fishbones first observed on the Poloidal Divertor Experiment (PDX). The modes are driven by energetic trapped ions at the fastion precession frequency. During a burst, the frequency changes most rapidly as the mode reaches its maximum amplitude. Larger amplitude bursts have larger growth rates and frequency chirps. Unlike PDX fishbones, the decay phase is highly variable and is usually shorter than the growth phase. Also, the waveform is highly distorted by higher harmonics during the latter portion of a burst. The radial mode structure alters its shape during the burst. Like PDX fishbones, the modes expel trapped ions in a ‘beacon’ with a definite phase relationship relative to the mode. Seven types of loss detectors measure the beacon. The losses scale linearly with mode amplitude. The neutron rate changes most rapidly at maximum mode amplitude but, depending on the loss diagnostic, the losses often peak a few cycles later. The non-ambipolar fast-ion losses cause a sudden change in toroidal rotation frequency across the entire plasma. In addition to an overall drop, the neutron signal oscillates in response to the wave. Unlike the beacon of lost particles, which maintains a fixed phase relative to the mode, the phase of the neutron oscillations steadily increases throughout the burst, with the greatest phase slippage occurring in the highly nonlinear phase near maximum mode amplitude US Department of Energy SC-G903402, DE-FC02-04ER54698, DE-FG02-07ER54917
- Published
- 2011
21. Transport of energetic ions due to sawteeth, Alfvén eigenmodes and microturbulence
- Author
-
T. L. Rhodes, M. A. Van Zeeland, R. E. Waltz, Cc Petty, C.M. Muscatello, M. Garcia-Munoz, G. R. McKee, M. Murakami, Y. B. Zhu, J. H. Yu, J. M. Park, R. K. Fisher, W. W. Heidbrink, G. M. Staebler, D. C. Pace, R. B. White, W. Zhang, Raffi Nazikian, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, and Universidad de Sevilla. RNM138: Física Nuclear Aplicada
- Subjects
Nuclear physics ,Physics ,Nuclear and High Energy Physics ,education.field_of_study ,Population ,Microturbulence ,Plasma ,Condensed Matter Physics ,education ,Ion - Abstract
Utilizing an array of new diagnostics and simulation/modelling techniques, recent DIII-D experiments have elucidated a variety of energetic ion transport behaviour in the presence of instabilities ranging from large-scale sawteeth to fine spatial scale microturbulence. Important new insights include sawteeth, such as those of the ITER baseline scenario, causing major redistribution of the energetic ion population; high levels of transport induced by low-amplitude Alfven eigenmodes can be caused by the integrated effect of a large number of simultaneous modes; ´ and microturbulence can contribute to the removal of alpha ash while having little effect on fusion alphas. This paper provides an overview of recent and upcoming results from the DIII-D Energetic Particles research programme. US Department of Energy SC-G903402, DE-FC02-04ER54698, DE-FG02-89ER53296, DE-FG02-08ER54999, DE-AC05-00OR22725, DE-AC02-09CH11466, DE-FG03-08ER54984, DE-FG02-07ER54917
- Published
- 2011
22. Comparison of L-mode regimes with enhanced confinement by impurity seeding in JET and DIII-D
- Author
-
G L Jackson, M Murakami, D R Baker, R Budny, M Charlet, M R deBaar, P Dumortier, T E Evans, R J Groebner, N C Hawkes, D L Hillis, L C Ingesson, E Joffrin, H R Koslowski, K D Lawson, G Maddison, G R McKee, A M Messiaen, P Monier-Garbet, M F F Nave, J Ongena, J Rapp, F Sartori, G M Staebler, M Stamp, J D Strachan, M Tokar, B Unterberg, M von Hellerman, M R Wade, and contributors to the EFDA-JET Work Programme
- Subjects
Jet (fluid) ,Materials science ,Joint European Torus ,Magnetic confinement fusion ,chemistry.chemical_element ,Plasma ,Condensed Matter Physics ,Thermal diffusivity ,Neutron temperature ,Neon ,Nuclear Energy and Engineering ,chemistry ,Physics::Plasma Physics ,Seeding ,ddc:530 ,Atomic physics - Abstract
Impurity seeding in both the Joint European Torus (JET) and DIII-D tokamaks has produced L-mode discharges with confinement enhancements comparable to H-mode and a near doubling of the core ion temperature when compared,to similar unseeded discharges. Although Z(eff) increases with the neon injection, the total neutron rate is as high, or higher, than reference discharges and the calculated thermal neutron rate increases dramatically in both devices. Modelling with the gyrokinetic simulation code shows a reduction in low k turbulence growth rates with neon injection decreasing to less than the E x B shearing rate, consistent with stabilization of ion temperature gradient modes in both JET and DIII-D. Reductions in ion thermal diffusivity are also observed with impurity seeding. Neoclassical m/n = 3/2 tearing modes limit the duration of best performance in DIII-D with neon injection, while n = 1 and n = 2 magnetohydrodynamic modes limit the performance in JET.
- Published
- 2002
23. Contrasting physics in wire array z pinch sources of 1-20 keV emission on the Z facility
- Author
-
J. Reneker, A. L. Velikovich, J. C. Cisneros, M. P. Vigil, Mark E. Savage, Mark Herrmann, W. A. Sygar, J. P. Apruzese, G. S. Dunham, M. Cleveland, Y.-K. Chong, G. R. McKee, J. W. Thornhill, M. Wu, S. Toledo, C. R. Ball, M. A. Sullivan, M. R. Lopez, N. Ouart, M. E. Cuneo, J. L. Giuliani, D. J. Ampleford, Christopher Jennings, N. W. Moore, N. B. Huynh, E. W. Breden, Daniel Sinars, A. J. York, A. Dasgupta, T. Strizic, D. Sandoval, John L. Porter, Gregory Rochau, M. D. Kernahan, A. D. Edens, C. A. Coverdale, D. W. Justus, T. C. Wagoner, K. L. Killebrew, A. L. Carlson, T. D. Mulville, G. Olivas, C. Cox, Derek C. Lamppa, D. S. Nielsen, M. C. Jones, A. J. Harvey-Thompson, L. P. Molina, S. B. Hansen, E. C. Harding, A. J. Maurer, P. W. Lake, G. Robertson, C. S. Speas, D. A. Graham, Brent Manley Jones, R. Focia, T. M. Flanagan, A. R. Laspe, F. W. Long, R. D. Scharberg, and J. K. Moore
- Subjects
Physics ,Photon ,Opacity ,Z-pinch ,Ionization ,Pinch ,Implosion ,Plasma ,Atomic physics ,Condensed Matter Physics ,Charged particle - Abstract
Imploding wire arrays on the 20 MA Z generator have recently provided some of the most powerful and energetic laboratory sources of multi-keV photons, including ∼375 kJ of Al K-shell emission (hν ∼ 1–2 keV), ∼80 kJ of stainless steel K-shell emission (hν ∼ 5–9 keV) and a kJ-level of Mo K-shell emission (hν ∼ 17 keV). While the global implosion dynamics of these different wire arrays are very similar, the physical process that dominates the emission from these x-ray sources fall into three broad categories. Al wire arrays produce a column of plasma with densities up to ∼3 × 1021 ions/cm3, where opacity inhibits the escape of K-shell photons. Significant structure from instabilities can reduce the density and increase the surface area, therefore increase the K-shell emission. In contrast, stainless steel wire arrays operate in a regime where achieving a high pinch temperature (achieved by thermalizing a high implosion kinetic energy) is critical and, while opacity is present, it has less impact on the pinch...
- Published
- 2014
24. Advances in validating gyrokinetic turbulence models against L- and H-mode plasmas
- Author
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W. A. Peebles, R. Prater, Long Zeng, Sterling Smith, Zheng Yan, G. M. Staebler, Christopher Holland, L. W. Schmitz, E. J. Doyle, J. E. Kinsey, Anne White, T. L. Rhodes, G. Wang, J. C. Hillesheim, J.C. DeBoo, R. E. Waltz, Jeff Candy, C.C. Petty, K. H. Burrell, and G. R. McKee
- Subjects
Physics ,Tokamak ,Turbulence ,Magnetic confinement fusion ,Condensed Matter Physics ,law.invention ,Computational physics ,Nonlinear system ,law ,Gyrokinetics ,Statistical physics ,Scaling ,Beam (structure) ,Dimensionless quantity - Abstract
Robust validation of predictive turbulent transport models requires quantitative comparisons to experimental measurements at multiple levels, over a range of physically relevant conditions. Toward this end, a series of carefully designed validation experiments has been performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] to obtain comprehensive multifield, multipoint, multiwavenumber fluctuation measurements and their scalings with key dimensionless parameters. The results of two representative validation studies are presented: an elongation scaling study performed in beam heated L-mode discharges and an electron heating power scan performed in quiescent H-mode (QH-mode) discharges. A 50% increase in the elongation κ is observed to lead to a ∼50% increase in energy confinement time τe and accompanying decrease in fluctuation levels, qualitatively consistent with a priori theoretical predictions and nonlinear GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] simulation...
- Published
- 2011
25. Measurements of the cross-phase angle between density and electron temperature fluctuations and comparison with gyrokinetic simulations
- Author
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R. E. Waltz, K. H. Burrell, Cc Petty, Long Zeng, G. Wang, Troy Carter, J. C. Hillesheim, Christopher Holland, T. L. Rhodes, E. J. Doyle, L. W. Schmitz, Anne White, G. M. Staebler, J.C. DeBoo, G. R. McKee, and W. A. Peebles
- Subjects
Core (optical fiber) ,Physics ,Electron density ,Tokamak ,law ,Phase angle ,Electron temperature ,Plasma diagnostics ,Plasma ,Electron ,Atomic physics ,Condensed Matter Physics ,law.invention - Abstract
This paper presents new measurements of the cross-phase angle, αneTe, between long-wavelength (kθρs
- Published
- 2010
26. Simultaneous measurement of core electron temperature and density fluctuations during electron cyclotron heating on DIII-D
- Author
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W. A. Peebles, Troy Carter, R. Prater, L. W. Schmitz, Morgan Shafer, K. H. Burrell, T. L. Rhodes, J.C. DeBoo, G. M. Staebler, G. R. McKee, and Anne White
- Subjects
Physics ,Tokamak ,DIII-D ,Cyclotron ,Magnetic confinement fusion ,Plasma ,Electron ,Condensed Matter Physics ,law.invention ,Physics::Plasma Physics ,law ,Electron temperature ,Plasma diagnostics ,Atomic physics - Abstract
New measurements show that long-wavelength k s 0.5 electron temperature fluctuations can play an important role in determining electron thermal transport in low-confinement mode L-mode tokamak plasmas. In neutral beam-heated L-mode tokamak plasmas, electron thermal transport and the amplitude of long-wavelength electron temperature fluctuations both increase in cases where local electron cyclotron heating ECH is used to modify the plasma profiles. In contrast, the amplitude of simultaneously measured long-wavelength density fluctuations does not significantly increase. Linear stability analysis indicates that the ratio of the trapped electron mode TEM to ion temperature gradient ITG mode growth rates increases in the cases with ECH. The increased importance of the TEM drive relative to the ITG mode drive in the cases with ECH may be associated with the increases in electron thermal transport and electron temperature fluctuations. © 2010 American Institute of Physics. doi:10.1063/1.3318469 The importance of long-wavelength turbulent fluctuations in determining electron thermal transport in the core of tokamak plasmas is of considerable interest to the field of magnetically confined fusion. In the absence of magnetohydrodynamic MHD instabilities, small amplitude 1%, low frequency ci, where ci is the ion cyclotron frequency turbulent fluctuations associated with drift-wavetype instabilities are widely believed to drive radial transport. 1 The turbulence driven transport can lead to heat and particle losses that reduce the performance of magnetically confined fusion devices. 2 One expectation from driftwave theory that can be tested directly is that the ratio of electron temperature and density fluctuation amplitudes, T ˜ e /Te /n /n, should scale with the ratio of linear growth rates of the trapped electron mode TEM and the ion temperature gradient ITG mode, TEM/ITG. 3,4 To test this, multifield fluctuation measurements are needed. Electron temperature fluctuations and density fluctuations have previously been studied in tokamak experiments 5‐7 during electron cyclotron heating ECH, but the two fluctuating fields were not measured simultaneously. We present here the first simultaneous measurements of long-wavelength electron temperature fluctuations and density fluctuations in the core of an L-mode tokamak plasma heated with neutral beams and ECH. The experiment was performed on the DIII-D tokamak major radius R=1.67 m, minor radius a=0.61 m. 8 The discharges have magnetic field BT2.0 T, plasma current Ip=1 MA, with edge safety factor q955.2 in the time period of interest, and are inner wall limited. Afirst discharge is heated with 2.5 MW of neutral beam power injected in the direction of the plasma current beginning early in time t=300 ms. The L-mode plasma of interest 1500t 1800 ms is sawtooth-free and MHD-free. In a second
- Published
- 2010
27. Dependence of the low to high confinement mode transition power threshold and turbulence flow shear on injected torque
- Author
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G. Wang, R. J. Groebner, Morgan Shafer, G. R. McKee, David Schlossberg, W. M. Solomon, K. H. Burrell, R.J. Fonck, and P. Gohil
- Subjects
Physics ,Tokamak ,Toroid ,Turbulence ,Plasma ,Condensed Matter Physics ,law.invention ,Ion ,Shear (sheet metal) ,High-confinement mode ,Physics::Plasma Physics ,law ,Atomic physics ,Beam (structure) - Abstract
The power required to induce a bifurcation from a low-confinement mode to a high-confinement mode in DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] plasmas is found to depend sensitively on the injected neutral beam torque and consequent toroidal rotation. Plasmas exhibit a factor of 2–4 reduction in this power threshold, dependent on ion ∇B drift direction. Correlated with this change, turbulence velocity measurements near 0.9
- Published
- 2009
28. Implementation and application of two synthetic diagnostics for validating simulations of core tokamak turbulence
- Author
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George Tynan, L. W. Schmitz, Christopher Holland, Jeff Candy, R. E. Waltz, Anne White, Morgan Shafer, and G. R. McKee
- Subjects
Physics ,Toroid ,Tokamak ,Turbulence ,Cyclotron ,Condensed Matter Physics ,law.invention ,Computational physics ,law ,Gyrokinetics ,Plasma diagnostics ,Emission spectrum ,Atomic physics ,Beam (structure) - Abstract
The deployment of multiple high-resolution, spatially localized fluctuation diagnostics on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] opens the door to a new level of core turbulence model validation. Toward this end, the implementation of synthetic diagnostics that model physical beam emission spectroscopy and correlation electron cyclotron emission diagnostics is presented. Initial results from their applications to local gyrokinetic simulations of two locations in a DIII-D L-mode discharge performed with the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] are also discussed. At normalized toroidal flux ρ=0.5, we find very good agreement between experiment and simulation in both the energy flows and fluctuation levels measured by both diagnostics. However, at ρ=0.75, GYRO underpredicts the observed energy flows by roughly a factor of 7, with rms fluctuation levels underpredicted by a factor of 3. Interestingly, at both locations we find good agreement in the sha...
- Published
- 2009
29. Optimizing stability, transport, and divertor operation through plasma shaping for steady-state scenario development in DIII-D
- Author
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J.R. Ferron, A.W. Hyatt, T.H. Osborne, R. J. Groebner, C. M. Greenfield, C. T. Holcomb, M. Murakami, W.P. West, T. W. Petrie, G.L. Jackson, J.C. DeBoo, G.D. Porter, M. Groth, H. Reimerdes, A. D. Turnbull, E. J. Doyle, C.E. Kessel, G. R. McKee, Morgan Shafer, P.A. Politzer, C. D. Challis, T. L. Rhodes, T.C. Luce, M. A. Makowski, R.J. La Haye, P.B. Snyder, R. Prater, and Jin Myung Park
- Subjects
Physics ,Tokamak ,Steady state ,DIII-D ,Divertor ,Plasma ,Mechanics ,Condensed Matter Physics ,Instability ,law.invention ,Bootstrap current ,Physics::Plasma Physics ,law ,Plasma shaping ,Atomic physics - Abstract
Recent studies on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] have elucidated key aspects of the dependence of stability, confinement, and density control on the plasma magnetic configuration, leading to the demonstration of nearly noninductive operation for >1 s with pressure 30% above the ideal no-wall stability limit. Achieving fully noninductive tokamak operation requires high pressure, good confinement, and density control through divertor pumping. Plasma geometry affects all of these. Ideal magnetohydrodynamics modeling of external kink stability suggests that it may be optimized by adjusting the shape parameter known as squareness (ζ). Optimizing kink stability leads to an increase in the maximum stable pressure. Experiments confirm that stability varies strongly with ζ, in agreement with the modeling. Optimization of kink stability via ζ is concurrent with an increase in the H-mode edge pressure pedestal stability. Global energy confinement is optimized at the lowest ζ tested, wi...
- Published
- 2009
30. Validation in fusion research: Towards guidelines and best practices
- Author
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D. R. Mikkelsen, Paul Terry, Martin Greenwald, D. P. Stotler, W. M. Nevins, G. R. McKee, David E. Newman, and J. N. Leboeuf
- Subjects
Mathematical model ,Hierarchy (mathematics) ,Computer science ,Best practice ,FOS: Physical sciences ,Magnetic confinement fusion ,Condensed Matter Physics ,computer.software_genre ,Physics - Plasma Physics ,Plasma Physics (physics.plasm-ph) ,Set (abstract data type) ,Identification (information) ,Data mining ,Metric (unit) ,Sensitivity (control systems) ,computer - Abstract
Because experiment/model comparisons in magnetic confinement fusion have not yet satisfied the requirements for validation as understood broadly, a set of approaches to validating mathematical models and numerical algorithms are recommended as good practices. Previously identified procedures, such as verification, qualification, and analysis of error and uncertainty, remain important. However, particular challenges intrinsic to fusion plasmas and physical measurement therein lead to identification of new or less familiar concepts that are also critical in validation. These include the primacy hierarchy, which tracks the integration of measurable quantities, and sensitivity analysis, which assesses how model output is apportioned to different sources of variation. The use of validation metrics for individual measurements is extended to multiple measurements, with provisions for the primacy hierarchy and sensitivity. This composite validation metric is essential for quantitatively evaluating comparisons with experiments. To mount successful and credible validation in magnetic fusion, a new culture of validation is envisaged., 27 pages, 1 table, 6 figures
- Published
- 2008
31. Coupling of global toroidal Alfvén eigenmodes and reversed shear Alfvén eigenmodes in DIII-D
- Author
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E. Ruskov, N. N. Gorelenkov, A. D. Turnbull, G. R. McKee, G. J. Kramer, M. A. Makowski, M. A. Van Zeeland, Max E Austin, William Heidbrink, and Raffi Nazikian
- Subjects
Physics ,Coupling (physics) ,Toroid ,Safety factor ,DIII-D ,Physics::Plasma Physics ,Normal mode ,Plasma diagnostics ,Plasma ,Magnetohydrodynamics ,Atomic physics ,Condensed Matter Physics ,Computational physics - Abstract
Reversed shear Alfv́n eigenmodes (RSAEs) are typically thought of as being localized near the minima in the magnetic safety factor profile, however, their spatial coupling to global toroidal Alfv́n eigenmodes (TAEs) has been observed in DIII-D discharges. For a decreasing minimum magnetic safety factor, the RSAE frequency chirps up through that of stable and unstable TAEs. Coupling creates a small gap at the frequency degeneracy point forming two distinct global modes. The core-localized RSAE mode structure changes and becomes temporarily global. Similarly, near the mode frequency crossing point, the global TAE extends deeper into the plasma core. The frequency splitting and spatial structure of the two modes throughout the various coupling stages, as measured by an array of internal fluctuation diagnostics, are in close agreement with linear ideal MHD calculations using the NOVA code. The implications of this coupling for eigenmode stability is also investigated and marked changes are noted throughout the coupling process. © 2007 American Institute of Physics.
- Published
- 2007
32. Interpretation of core localized Alfvén eigenmodes in DIII-D and Joint European Torus reversed magnetic shear plasmas
- Author
-
T. L. Rhodes, Herbert L Berk, G. J. Kramer, S. E. Sharapov, S. D. Pinches, Guoyong Fu, W.M. Solomon, M. A. Van Zeeland, N. N. Gorelenkov, Jet-Efda Contributors, G. R. McKee, B. Alper, Raffi Nazikian, and M.R. de Baar
- Subjects
Physics ,Jet (fluid) ,Toroid ,DIII-D ,Physics::Plasma Physics ,Joint European Torus ,Magnetohydrodynamic drive ,Plasma ,Magnetohydrodynamics ,Atomic physics ,Condensed Matter Physics ,Beam (structure) - Abstract
Reversed shear Alfven eigenmodes (RSAE) that were observed in the Joint European Torus (JET) [P. H. Rebut and B. E. Keen, Fusion Technol.11, 13 (1987)] and DIII-D [J. L. Luxon, Nucl. Fusion42, 614 (2002)] are studied with the ideal magnetohydrodynamic code NOVA-K [C. Z. Cheng, Phys. Rep.211, 1 (1992)]. It was found that the frequency behavior of the RSAEs can be described accurately by the NOVA-K code when plasma compressibility effects and toroidal plasma rotation are taken into account. For the mode activity on JET, the calculated drive exceeds the mode damping rate, consistent with experimental observations, while on DIII-D the growth rate from neutral beam ions for modes with high toroidal mode numbers is insufficient to account for the excitation of the modes and a major part of the drive comes from the background plasma.
- Published
- 2006
33. Edge-localized mode dynamics and transport in the scrape-off layer of the DIII-D tokamak
- Author
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Dmitry Rudakov, K. H. Burrell, W.P. West, G. Wang, G.D. Porter, P.C. Stangeby, Taiki Takahashi, Todd Evans, R.J. Colchin, Anthony Leonard, M. Groth, R.A. Moyer, D. S. Gray, J.G. Watkins, N. S. Wolf, E. M. Hollmann, Lei Zeng, S.L. Allen, M.J. Schaffer, C.J. Lasnier, P. B. Snyder, G. R. McKee, Jose Boedo, M.A. Mahdavi, R.J. Fonck, and Max E. Fenstermacher
- Subjects
Physics ,Tokamak ,DIII-D ,law ,Energy flux ,Magnetic confinement fusion ,Electron temperature ,Plasma diagnostics ,Plasma ,Atomic physics ,Condensed Matter Physics ,Edge-localized mode ,law.invention - Abstract
High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge-localized modes (ELMs) are produced in the low field side, are poloidally localized and are composed of fast bursts (∼20 to 40μs long) of hot, dense plasma on a background of less dense, colder plasma (∼5×1018m−3, 50 eV) possibly created by the bursts themselves. The ELMs travel radially in the scrape-off layer (SOL), starting at the separatrix at ∼450m∕s, and slow down to ∼150m∕s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length (∼1.2 to 1.5 cm) is much shorter than the density decay length (∼3 to 8 cm), and the latter decreases with increasing pedestal (and SOL) density. The local particle and energy flux (assuming Ti=Te) at the midplane wall during the bursts are 10% to 50% (∼1 to 2×1021m−2s−1) and 1% to...
- Published
- 2005
34. Edge localized mode control with an edge resonant magnetic perturbation
- Author
-
M. Groth, J. H. Harris, M. R. Wade, R. J. Groebner, J.G. Watkins, H. Reimerdes, G. Wang, E. J. Doyle, K.H. Finken, G.L. Jackson, W.P. West, R.A. Moyer, M.E. Fenstermacher, P. B. Snyder, C.J. Lasnier, P.R. Thomas, T. L. Rhodes, P. Gohil, Jose Boedo, M. Becoulet, G. R. McKee, T.H. Osborne, Long Zeng, A.W. Leonard, Dmitry Rudakov, M.J. Schaffer, Todd Evans, and R.J. La Haye
- Subjects
Physics ,Work (thermodynamics) ,Condensed matter physics ,Magnetic confinement fusion ,Magnetic perturbation ,Magnetohydrodynamics ,Edge (geometry) ,Atomic physics ,Condensed Matter Physics ,Edge-localized mode ,Magnetic field ,Plasma density - Abstract
This work was funded by the U.S. Department of Energy under Grant Nos. DE-FC02-04ER54698, DE-FG02- 04ER54758, DE-FG03-01ER54615, W-7405-ENG-48, DEFG03-96ER54373, DE-FG02-89ER53297, DE-AC05- 00OR22725, and DE-AC04-94AL85000.
- Published
- 2005
35. Impurity-induced turbulence suppression and reduced transport in the DIII-D tokamak
- Author
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G. M. Staebler, Curtis L. Rettig, J.A. Boedo, B. W. Rice, R.J. Fonck, C. Rost, B. Unterberg, R.J. La Haye, M. W. Jakubowski, Daniel Thomas, Masakatsu Murakami, W.P. West, Richard Sydora, G. R. McKee, K. H. Burrell, D.R. Ernst, J. Ongena, G.L. Jackson, M. R. Wade, N.H. Brooks, and A. M. Messiaen
- Subjects
Physics ,Tokamak ,DIII-D ,Turbulence ,chemistry.chemical_element ,Plasma ,Condensed Matter Physics ,law.invention ,Neon ,symbols.namesake ,chemistry ,Physics::Plasma Physics ,law ,symbols ,Langmuir probe ,Nuclear fusion ,Plasma diagnostics ,Atomic physics - Abstract
Long wavelength turbulence as well as heat and momentum transport are significantly reduced in the DIII-D tokamak [Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] as a result of neon seeding of a low confinement mode negative central shear discharge. Correspondingly, the energy confinement time increases by up to 80%. Fully saturated turbulence measurements near ρ=0.7 (ρ=r/a) in the wave number range 0.1⩽k⊥ρs⩽0.6, obtained with beam emission spectroscopy, exhibit a significant reduction of fluctuation power after neon injection. Fluctuation measurements obtained with far infrared scattering also show a reduction of turbulence in the core, while the Langmuir probe array measures reduced particle flux in the edge and scrape-off layer. Gyrokinetic linear stability simulations of these plasmas are qualitatively consistent, showing a reduction in the growth rate of ion temperature gradient driven modes for 0
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