Overview of physics results from the conclusive operation of the National Spherical Torus Experiment

S. A. Sabbagh, J. W. Ahn, J. Allain, R. Andre, A. Balbaky, R. Bastasz, D. Battaglia, M. Bell, R. Bell, P. Beiersdorfer, E. Belova, J. Berkery, R. Betti, J. Bialek, T. Bigelow, M. Bitter, J. Boedo, P. Bonoli, A. Boozer, A. Bortolon & 160 others D. Boyle, D. Brennan, J. Breslau, R. Buttery, J. Canik, G. Caravelli, C. Chang, N. Crocker, D. Darrow, B. Davis, L. Delgado-Aparicio, A. Diallo, S. Ding, D. D'Ippolito, C. Domier, W. Dorland, S. Ethier, T. Evans, J. Ferron, M. Finkenthal, J. Foley, R. Fonck, R. Frazin, E. Fredrickson, G. Fu, D. Gates, S. Gerhardt, A. Glasser, N. Gorelenkov, T. Gray, Y. Guo, W. Guttenfelder, T. Hahm, R. Harvey, A. Hassanein, W. Heidbrink, K. Hill, Y. Hirooka, E. B. Hooper, J. Hosea, D. Humphreys, K. Indireshkumar, F. Jaeger, T. Jarboe, S. Jardin, M. Jaworski, R. Kaita, J. Kallman, O. Katsuro-Hopkins, S. Kaye, C. Kessel, J. Kim, E. Kolemen, G. Kramer, S. Krasheninnikov, S. Kubota, H. Kugel, R. J. La Haye, L. Lao, B. Leblanc, W. Lee, K. Lee, J. Leuer, F. Levinton, Y. Liang, D. Liu, J. Lore, N. Luhmann, R. Maingi, R. Majeski, J. Manickam, D. Mansfield, R. Maqueda, E. Mazzucato, A. McLean, D. McCune, B. McGeehan, G. McKee, S. Medley, E. Meier, J. Menard, M. Menon, H. Meyer, D. Mikkelsen, G. Miloshevsky, D. Mueller, T. Munsat, J. Myra, B. Nelson, N. Nishino, R. Nygren, M. Ono, T. Osborne, H. Park, J. Park, Y. S. Park, S. Paul, W. Peebles, B. Penaflor, R. J. Perkins, C. Phillips, A. Pigarov, M. Podesta, J. Preinhaelter, R. Raman, Y. Ren, G. Rewoldt, T. Rognlien, P. Ross, C. Rowley, E. Ruskov, D. Russell, D. Ruzic, P. Ryan, M. Schaffer, E. Schuster, F. Scotti, K. Shaing, V. Shevchenko, K. Shinohara, V. Sizyuk, C. H. Skinner, A. Smirnov, D. Smith, P. Snyder, W. Solomon, A. Sontag, V. Soukhanovskii, T. Stoltzfus-Dueck, D. Stotler, B. Stratton, D. Stutman, H. Takahashi, Y. Takase, N. Tamura, X. Tang, G. Taylor, C. Taylor, K. Tritz, D. Tsarouhas, M. Umansky, J. Urban, E. Untergberg, M. Walker, W. Wampler, W. Wang, J. Whaley, R. White, J. Wilgen, R. Wilson, K. L. Wong, J. Wright, Z. Xia, D. Youchison, G. Yu, H. Yuh, L. Zakharov, D. Zemlyanov, G. Zimmer, S. J. Zweben

Research output: Research - peer-reviewReview article

Abstract

Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique ST operational space is leveraged to test physics theories for next-step tokamak operation, including ITER. Present research also examines implications for the coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified for varied wall conditions exhibits a strong improvement of BTτE with decreased electron collisionality, accentuated by lithium (Li) wall conditioning. This result is consistent with nonlinear microtearing simulations that match the experimental electron diffusivity quantitatively and predict reduced electron heat transport at lower collisionality. Beam-emission spectroscopy measurements in the steep gradient region of the pedestal indicate the poloidal correlation length of turbulence of about ten ion gyroradii increases at higher electron density gradient and lower Ti gradient, consistent with turbulence caused by trapped electron instabilities. Density fluctuations in the pedestal top region indicate ion-scale microturbulence compatible with ion temperature gradient and/or kinetic ballooning mode instabilities. Plasma characteristics change nearly continuously with increasing Li evaporation and edge localized modes (ELMs) stabilize due to edge density gradient alteration. Global mode stability studies show stabilizing resonant kinetic effects are enhanced at lower collisionality, but in stark contrast have almost no dependence on collisionality when the plasma is off-resonance. Combined resistive wall mode radial and poloidal field sensor feedback was used to control n = 1 perturbations and improve stability. The disruption probability due to unstable resistive wall modes (RWMs) was surprisingly reduced at very high βN/li > 10 consistent with low frequency magnetohydrodynamic spectroscopy measurements of mode stability. Greater instability seen at intermediate βN is consistent with decreased kinetic RWM stabilization. A model-based RWM state-space controller produced long-pulse discharges exceeding βN = 6.4 and βN/li = 13. Precursor analysis shows 96.3% of disruptions can be predicted with 10 ms warning and a false positive rate of only 2.8%. Disruption halo currents rotate toroidally and can have significant toroidal asymmetry. Global kinks cause measured fast ion redistribution, with full-orbit calculations showing redistribution from the core outward and towards V/V = 1 where destabilizing compressional Alfvén eigenmode resonances are expected. Applied 3D fields altered global Alfvén eigenmode characteristics. High-harmonic fast-wave (HHFW) power couples to field lines across the entire width of the scrape-off layer, showing the importance of the inclusion of this phenomenon in designing future RF systems. The snowflake divertor configuration enhanced by radiative detachment showed large reductions in both steady-state and ELM heat fluxes (ELMing peak values down from 19 MW m-2 to less than 1.5 MW m-2). Toroidal asymmetry of heat deposition was observed during ELMs or by 3D fields. The heating power required for accessing H-mode decreased by 30% as the triangularity was decreased by moving the X-point to larger radius, consistent with calculations of the dependence of E × B shear in the edge region on ion heat flux and X-point radius. Co-axial helicity injection reduced the inductive start-up flux, with plasmas ramped to 1 MA requiring 35% less inductive flux. Non-inductive current fraction (NICF) up to 65% is reached experimentally with neutral beam injection at plasma current Ip = 0.7 MA and between 70-100% with HHFW application at Ip = 0.3 MA. NSTX-U scenario development calculations project 100% NICF for a large range of 0.6 < Ip (MA) < 1.35.

LanguageEnglish (US)
Article number104007
JournalNuclear Fusion
Volume53
Issue number10
DOIs
StatePublished - Oct 2013

Fingerprint

physics
gradients
ions
electrons
kinetics
heat flux
lithium
turbulence
asymmetry
harmonics
heat
radii
spectroscopy
orbit calculation
ballooning modes
pilot plants
beam injection
warning
plasma currents
neutral beams

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Sabbagh, S. A., Ahn, J. W., Allain, J., Andre, R., Balbaky, A., Bastasz, R., ... Zweben, S. J. (2013). Overview of physics results from the conclusive operation of the National Spherical Torus Experiment. Nuclear Fusion, 53(10), [104007]. DOI: 10.1088/0029-5515/53/10/104007

Overview of physics results from the conclusive operation of the National Spherical Torus Experiment. / Sabbagh, S. A.; Ahn, J. W.; Allain, J.; Andre, R.; Balbaky, A.; Bastasz, R.; Battaglia, D.; Bell, M.; Bell, R.; Beiersdorfer, P.; Belova, E.; Berkery, J.; Betti, R.; Bialek, J.; Bigelow, T.; Bitter, M.; Boedo, J.; Bonoli, P.; Boozer, A.; Bortolon, A.; Boyle, D.; Brennan, D.; Breslau, J.; Buttery, R.; Canik, J.; Caravelli, G.; Chang, C.; Crocker, N.; Darrow, D.; Davis, B.; Delgado-Aparicio, L.; Diallo, A.; Ding, S.; D'Ippolito, D.; Domier, C.; Dorland, W.; Ethier, S.; Evans, T.; Ferron, J.; Finkenthal, M.; Foley, J.; Fonck, R.; Frazin, R.; Fredrickson, E.; Fu, G.; Gates, D.; Gerhardt, S.; Glasser, A.; Gorelenkov, N.; Gray, T.; Guo, Y.; Guttenfelder, W.; Hahm, T.; Harvey, R.; Hassanein, A.; Heidbrink, W.; Hill, K.; Hirooka, Y.; Hooper, E. B.; Hosea, J.; Humphreys, D.; Indireshkumar, K.; Jaeger, F.; Jarboe, T.; Jardin, S.; Jaworski, M.; Kaita, R.; Kallman, J.; Katsuro-Hopkins, O.; Kaye, S.; Kessel, C.; Kim, J.; Kolemen, E.; Kramer, G.; Krasheninnikov, S.; Kubota, S.; Kugel, H.; La Haye, R. J.; Lao, L.; Leblanc, B.; Lee, W.; Lee, K.; Leuer, J.; Levinton, F.; Liang, Y.; Liu, D.; Lore, J.; Luhmann, N.; Maingi, R.; Majeski, R.; Manickam, J.; Mansfield, D.; Maqueda, R.; Mazzucato, E.; McLean, A.; McCune, D.; McGeehan, B.; McKee, G.; Medley, S.; Meier, E.; Menard, J.; Menon, M.; Meyer, H.; Mikkelsen, D.; Miloshevsky, G.; Mueller, D.; Munsat, T.; Myra, J.; Nelson, B.; Nishino, N.; Nygren, R.; Ono, M.; Osborne, T.; Park, H.; Park, J.; Park, Y. S.; Paul, S.; Peebles, W.; Penaflor, B.; Perkins, R. J.; Phillips, C.; Pigarov, A.; Podesta, M.; Preinhaelter, J.; Raman, R.; Ren, Y.; Rewoldt, G.; Rognlien, T.; Ross, P.; Rowley, C.; Ruskov, E.; Russell, D.; Ruzic, D.; Ryan, P.; Schaffer, M.; Schuster, E.; Scotti, F.; Shaing, K.; Shevchenko, V.; Shinohara, K.; Sizyuk, V.; Skinner, C. H.; Smirnov, A.; Smith, D.; Snyder, P.; Solomon, W.; Sontag, A.; Soukhanovskii, V.; Stoltzfus-Dueck, T.; Stotler, D.; Stratton, B.; Stutman, D.; Takahashi, H.; Takase, Y.; Tamura, N.; Tang, X.; Taylor, G.; Taylor, C.; Tritz, K.; Tsarouhas, D.; Umansky, M.; Urban, J.; Untergberg, E.; Walker, M.; Wampler, W.; Wang, W.; Whaley, J.; White, R.; Wilgen, J.; Wilson, R.; Wong, K. L.; Wright, J.; Xia, Z.; Youchison, D.; Yu, G.; Yuh, H.; Zakharov, L.; Zemlyanov, D.; Zimmer, G.; Zweben, S. J.

In: Nuclear Fusion, Vol. 53, No. 10, 104007, 10.2013.

Research output: Research - peer-reviewReview article

Sabbagh, SA, Ahn, JW, Allain, J, Andre, R, Balbaky, A, Bastasz, R, Battaglia, D, Bell, M, Bell, R, Beiersdorfer, P, Belova, E, Berkery, J, Betti, R, Bialek, J, Bigelow, T, Bitter, M, Boedo, J, Bonoli, P, Boozer, A, Bortolon, A, Boyle, D, Brennan, D, Breslau, J, Buttery, R, Canik, J, Caravelli, G, Chang, C, Crocker, N, Darrow, D, Davis, B, Delgado-Aparicio, L, Diallo, A, Ding, S, D'Ippolito, D, Domier, C, Dorland, W, Ethier, S, Evans, T, Ferron, J, Finkenthal, M, Foley, J, Fonck, R, Frazin, R, Fredrickson, E, Fu, G, Gates, D, Gerhardt, S, Glasser, A, Gorelenkov, N, Gray, T, Guo, Y, Guttenfelder, W, Hahm, T, Harvey, R, Hassanein, A, Heidbrink, W, Hill, K, Hirooka, Y, Hooper, EB, Hosea, J, Humphreys, D, Indireshkumar, K, Jaeger, F, Jarboe, T, Jardin, S, Jaworski, M, Kaita, R, Kallman, J, Katsuro-Hopkins, O, Kaye, S, Kessel, C, Kim, J, Kolemen, E, Kramer, G, Krasheninnikov, S, Kubota, S, Kugel, H, La Haye, RJ, Lao, L, Leblanc, B, Lee, W, Lee, K, Leuer, J, Levinton, F, Liang, Y, Liu, D, Lore, J, Luhmann, N, Maingi, R, Majeski, R, Manickam, J, Mansfield, D, Maqueda, R, Mazzucato, E, McLean, A, McCune, D, McGeehan, B, McKee, G, Medley, S, Meier, E, Menard, J, Menon, M, Meyer, H, Mikkelsen, D, Miloshevsky, G, Mueller, D, Munsat, T, Myra, J, Nelson, B, Nishino, N, Nygren, R, Ono, M, Osborne, T, Park, H, Park, J, Park, YS, Paul, S, Peebles, W, Penaflor, B, Perkins, RJ, Phillips, C, Pigarov, A, Podesta, M, Preinhaelter, J, Raman, R, Ren, Y, Rewoldt, G, Rognlien, T, Ross, P, Rowley, C, Ruskov, E, Russell, D, Ruzic, D, Ryan, P, Schaffer, M, Schuster, E, Scotti, F, Shaing, K, Shevchenko, V, Shinohara, K, Sizyuk, V, Skinner, CH, Smirnov, A, Smith, D, Snyder, P, Solomon, W, Sontag, A, Soukhanovskii, V, Stoltzfus-Dueck, T, Stotler, D, Stratton, B, Stutman, D, Takahashi, H, Takase, Y, Tamura, N, Tang, X, Taylor, G, Taylor, C, Tritz, K, Tsarouhas, D, Umansky, M, Urban, J, Untergberg, E, Walker, M, Wampler, W, Wang, W, Whaley, J, White, R, Wilgen, J, Wilson, R, Wong, KL, Wright, J, Xia, Z, Youchison, D, Yu, G, Yuh, H, Zakharov, L, Zemlyanov, D, Zimmer, G & Zweben, SJ 2013, 'Overview of physics results from the conclusive operation of the National Spherical Torus Experiment' Nuclear Fusion, vol 53, no. 10, 104007. DOI: 10.1088/0029-5515/53/10/104007
Sabbagh SA, Ahn JW, Allain J, Andre R, Balbaky A, Bastasz R et al. Overview of physics results from the conclusive operation of the National Spherical Torus Experiment. Nuclear Fusion. 2013 Oct;53(10). 104007. Available from, DOI: 10.1088/0029-5515/53/10/104007
Sabbagh, S. A. ; Ahn, J. W. ; Allain, J. ; Andre, R. ; Balbaky, A. ; Bastasz, R. ; Battaglia, D. ; Bell, M. ; Bell, R. ; Beiersdorfer, P. ; Belova, E. ; Berkery, J. ; Betti, R. ; Bialek, J. ; Bigelow, T. ; Bitter, M. ; Boedo, J. ; Bonoli, P. ; Boozer, A. ; Bortolon, A. ; Boyle, D. ; Brennan, D. ; Breslau, J. ; Buttery, R. ; Canik, J. ; Caravelli, G. ; Chang, C. ; Crocker, N. ; Darrow, D. ; Davis, B. ; Delgado-Aparicio, L. ; Diallo, A. ; Ding, S. ; D'Ippolito, D. ; Domier, C. ; Dorland, W. ; Ethier, S. ; Evans, T. ; Ferron, J. ; Finkenthal, M. ; Foley, J. ; Fonck, R. ; Frazin, R. ; Fredrickson, E. ; Fu, G. ; Gates, D. ; Gerhardt, S. ; Glasser, A. ; Gorelenkov, N. ; Gray, T. ; Guo, Y. ; Guttenfelder, W. ; Hahm, T. ; Harvey, R. ; Hassanein, A. ; Heidbrink, W. ; Hill, K. ; Hirooka, Y. ; Hooper, E. B. ; Hosea, J. ; Humphreys, D. ; Indireshkumar, K. ; Jaeger, F. ; Jarboe, T. ; Jardin, S. ; Jaworski, M. ; Kaita, R. ; Kallman, J. ; Katsuro-Hopkins, O. ; Kaye, S. ; Kessel, C. ; Kim, J. ; Kolemen, E. ; Kramer, G. ; Krasheninnikov, S. ; Kubota, S. ; Kugel, H. ; La Haye, R. J. ; Lao, L. ; Leblanc, B. ; Lee, W. ; Lee, K. ; Leuer, J. ; Levinton, F. ; Liang, Y. ; Liu, D. ; Lore, J. ; Luhmann, N. ; Maingi, R. ; Majeski, R. ; Manickam, J. ; Mansfield, D. ; Maqueda, R. ; Mazzucato, E. ; McLean, A. ; McCune, D. ; McGeehan, B. ; McKee, G. ; Medley, S. ; Meier, E. ; Menard, J. ; Menon, M. ; Meyer, H. ; Mikkelsen, D. ; Miloshevsky, G. ; Mueller, D. ; Munsat, T. ; Myra, J. ; Nelson, B. ; Nishino, N. ; Nygren, R. ; Ono, M. ; Osborne, T. ; Park, H. ; Park, J. ; Park, Y. S. ; Paul, S. ; Peebles, W. ; Penaflor, B. ; Perkins, R. J. ; Phillips, C. ; Pigarov, A. ; Podesta, M. ; Preinhaelter, J. ; Raman, R. ; Ren, Y. ; Rewoldt, G. ; Rognlien, T. ; Ross, P. ; Rowley, C. ; Ruskov, E. ; Russell, D. ; Ruzic, D. ; Ryan, P. ; Schaffer, M. ; Schuster, E. ; Scotti, F. ; Shaing, K. ; Shevchenko, V. ; Shinohara, K. ; Sizyuk, V. ; Skinner, C. H. ; Smirnov, A. ; Smith, D. ; Snyder, P. ; Solomon, W. ; Sontag, A. ; Soukhanovskii, V. ; Stoltzfus-Dueck, T. ; Stotler, D. ; Stratton, B. ; Stutman, D. ; Takahashi, H. ; Takase, Y. ; Tamura, N. ; Tang, X. ; Taylor, G. ; Taylor, C. ; Tritz, K. ; Tsarouhas, D. ; Umansky, M. ; Urban, J. ; Untergberg, E. ; Walker, M. ; Wampler, W. ; Wang, W. ; Whaley, J. ; White, R. ; Wilgen, J. ; Wilson, R. ; Wong, K. L. ; Wright, J. ; Xia, Z. ; Youchison, D. ; Yu, G. ; Yuh, H. ; Zakharov, L. ; Zemlyanov, D. ; Zimmer, G. ; Zweben, S. J./ Overview of physics results from the conclusive operation of the National Spherical Torus Experiment. In: Nuclear Fusion. 2013 ; Vol. 53, No. 10.
@article{6d6616721df2464eab11b268ac371000,
title = "Overview of physics results from the conclusive operation of the National Spherical Torus Experiment",
abstract = "Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique ST operational space is leveraged to test physics theories for next-step tokamak operation, including ITER. Present research also examines implications for the coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified for varied wall conditions exhibits a strong improvement of BTτE with decreased electron collisionality, accentuated by lithium (Li) wall conditioning. This result is consistent with nonlinear microtearing simulations that match the experimental electron diffusivity quantitatively and predict reduced electron heat transport at lower collisionality. Beam-emission spectroscopy measurements in the steep gradient region of the pedestal indicate the poloidal correlation length of turbulence of about ten ion gyroradii increases at higher electron density gradient and lower Ti gradient, consistent with turbulence caused by trapped electron instabilities. Density fluctuations in the pedestal top region indicate ion-scale microturbulence compatible with ion temperature gradient and/or kinetic ballooning mode instabilities. Plasma characteristics change nearly continuously with increasing Li evaporation and edge localized modes (ELMs) stabilize due to edge density gradient alteration. Global mode stability studies show stabilizing resonant kinetic effects are enhanced at lower collisionality, but in stark contrast have almost no dependence on collisionality when the plasma is off-resonance. Combined resistive wall mode radial and poloidal field sensor feedback was used to control n = 1 perturbations and improve stability. The disruption probability due to unstable resistive wall modes (RWMs) was surprisingly reduced at very high βN/li > 10 consistent with low frequency magnetohydrodynamic spectroscopy measurements of mode stability. Greater instability seen at intermediate βN is consistent with decreased kinetic RWM stabilization. A model-based RWM state-space controller produced long-pulse discharges exceeding βN = 6.4 and βN/li = 13. Precursor analysis shows 96.3% of disruptions can be predicted with 10 ms warning and a false positive rate of only 2.8%. Disruption halo currents rotate toroidally and can have significant toroidal asymmetry. Global kinks cause measured fast ion redistribution, with full-orbit calculations showing redistribution from the core outward and towards V∥/V = 1 where destabilizing compressional Alfvén eigenmode resonances are expected. Applied 3D fields altered global Alfvén eigenmode characteristics. High-harmonic fast-wave (HHFW) power couples to field lines across the entire width of the scrape-off layer, showing the importance of the inclusion of this phenomenon in designing future RF systems. The snowflake divertor configuration enhanced by radiative detachment showed large reductions in both steady-state and ELM heat fluxes (ELMing peak values down from 19 MW m-2 to less than 1.5 MW m-2). Toroidal asymmetry of heat deposition was observed during ELMs or by 3D fields. The heating power required for accessing H-mode decreased by 30% as the triangularity was decreased by moving the X-point to larger radius, consistent with calculations of the dependence of E × B shear in the edge region on ion heat flux and X-point radius. Co-axial helicity injection reduced the inductive start-up flux, with plasmas ramped to 1 MA requiring 35% less inductive flux. Non-inductive current fraction (NICF) up to 65% is reached experimentally with neutral beam injection at plasma current Ip = 0.7 MA and between 70-100% with HHFW application at Ip = 0.3 MA. NSTX-U scenario development calculations project 100% NICF for a large range of 0.6 < Ip (MA) < 1.35.",
author = "Sabbagh, {S. A.} and Ahn, {J. W.} and J. Allain and R. Andre and A. Balbaky and R. Bastasz and D. Battaglia and M. Bell and R. Bell and P. Beiersdorfer and E. Belova and J. Berkery and R. Betti and J. Bialek and T. Bigelow and M. Bitter and J. Boedo and P. Bonoli and A. Boozer and A. Bortolon and D. Boyle and D. Brennan and J. Breslau and R. Buttery and J. Canik and G. Caravelli and C. Chang and N. Crocker and D. Darrow and B. Davis and L. Delgado-Aparicio and A. Diallo and S. Ding and D. D'Ippolito and C. Domier and W. Dorland and S. Ethier and T. Evans and J. Ferron and M. Finkenthal and J. Foley and R. Fonck and R. Frazin and E. Fredrickson and G. Fu and D. Gates and S. Gerhardt and A. Glasser and N. Gorelenkov and T. Gray and Y. Guo and W. Guttenfelder and T. Hahm and R. Harvey and A. Hassanein and W. Heidbrink and K. Hill and Y. Hirooka and Hooper, {E. B.} and J. Hosea and D. Humphreys and K. Indireshkumar and F. Jaeger and T. Jarboe and S. Jardin and M. Jaworski and R. Kaita and J. Kallman and O. Katsuro-Hopkins and S. Kaye and C. Kessel and J. Kim and E. Kolemen and G. Kramer and S. Krasheninnikov and S. Kubota and H. Kugel and {La Haye}, {R. J.} and L. Lao and B. Leblanc and W. Lee and K. Lee and J. Leuer and F. Levinton and Y. Liang and D. Liu and J. Lore and N. Luhmann and R. Maingi and R. Majeski and J. Manickam and D. Mansfield and R. Maqueda and E. Mazzucato and A. McLean and D. McCune and B. McGeehan and G. McKee and S. Medley and E. Meier and J. Menard and M. Menon and H. Meyer and D. Mikkelsen and G. Miloshevsky and D. Mueller and T. Munsat and J. Myra and B. Nelson and N. Nishino and R. Nygren and M. Ono and T. Osborne and H. Park and J. Park and Park, {Y. S.} and S. Paul and W. Peebles and B. Penaflor and Perkins, {R. J.} and C. Phillips and A. Pigarov and M. Podesta and J. Preinhaelter and R. Raman and Y. Ren and G. Rewoldt and T. Rognlien and P. Ross and C. Rowley and E. Ruskov and D. Russell and D. Ruzic and P. Ryan and M. Schaffer and E. Schuster and F. Scotti and K. Shaing and V. Shevchenko and K. Shinohara and V. Sizyuk and Skinner, {C. H.} and A. Smirnov and D. Smith and P. Snyder and W. Solomon and A. Sontag and V. Soukhanovskii and T. Stoltzfus-Dueck and D. Stotler and B. Stratton and D. Stutman and H. Takahashi and Y. Takase and N. Tamura and X. Tang and G. Taylor and C. Taylor and K. Tritz and D. Tsarouhas and M. Umansky and J. Urban and E. Untergberg and M. Walker and W. Wampler and W. Wang and J. Whaley and R. White and J. Wilgen and R. Wilson and Wong, {K. L.} and J. Wright and Z. Xia and D. Youchison and G. Yu and H. Yuh and L. Zakharov and D. Zemlyanov and G. Zimmer and Zweben, {S. J.}",
year = "2013",
month = "10",
doi = "10.1088/0029-5515/53/10/104007",
volume = "53",
journal = "Nuclear Fusion",
issn = "0029-5515",
publisher = "IOP Publishing Ltd.",
number = "10",

}

TY - JOUR

T1 - Overview of physics results from the conclusive operation of the National Spherical Torus Experiment

AU - Sabbagh,S. A.

AU - Ahn,J. W.

AU - Allain,J.

AU - Andre,R.

AU - Balbaky,A.

AU - Bastasz,R.

AU - Battaglia,D.

AU - Bell,M.

AU - Bell,R.

AU - Beiersdorfer,P.

AU - Belova,E.

AU - Berkery,J.

AU - Betti,R.

AU - Bialek,J.

AU - Bigelow,T.

AU - Bitter,M.

AU - Boedo,J.

AU - Bonoli,P.

AU - Boozer,A.

AU - Bortolon,A.

AU - Boyle,D.

AU - Brennan,D.

AU - Breslau,J.

AU - Buttery,R.

AU - Canik,J.

AU - Caravelli,G.

AU - Chang,C.

AU - Crocker,N.

AU - Darrow,D.

AU - Davis,B.

AU - Delgado-Aparicio,L.

AU - Diallo,A.

AU - Ding,S.

AU - D'Ippolito,D.

AU - Domier,C.

AU - Dorland,W.

AU - Ethier,S.

AU - Evans,T.

AU - Ferron,J.

AU - Finkenthal,M.

AU - Foley,J.

AU - Fonck,R.

AU - Frazin,R.

AU - Fredrickson,E.

AU - Fu,G.

AU - Gates,D.

AU - Gerhardt,S.

AU - Glasser,A.

AU - Gorelenkov,N.

AU - Gray,T.

AU - Guo,Y.

AU - Guttenfelder,W.

AU - Hahm,T.

AU - Harvey,R.

AU - Hassanein,A.

AU - Heidbrink,W.

AU - Hill,K.

AU - Hirooka,Y.

AU - Hooper,E. B.

AU - Hosea,J.

AU - Humphreys,D.

AU - Indireshkumar,K.

AU - Jaeger,F.

AU - Jarboe,T.

AU - Jardin,S.

AU - Jaworski,M.

AU - Kaita,R.

AU - Kallman,J.

AU - Katsuro-Hopkins,O.

AU - Kaye,S.

AU - Kessel,C.

AU - Kim,J.

AU - Kolemen,E.

AU - Kramer,G.

AU - Krasheninnikov,S.

AU - Kubota,S.

AU - Kugel,H.

AU - La Haye,R. J.

AU - Lao,L.

AU - Leblanc,B.

AU - Lee,W.

AU - Lee,K.

AU - Leuer,J.

AU - Levinton,F.

AU - Liang,Y.

AU - Liu,D.

AU - Lore,J.

AU - Luhmann,N.

AU - Maingi,R.

AU - Majeski,R.

AU - Manickam,J.

AU - Mansfield,D.

AU - Maqueda,R.

AU - Mazzucato,E.

AU - McLean,A.

AU - McCune,D.

AU - McGeehan,B.

AU - McKee,G.

AU - Medley,S.

AU - Meier,E.

AU - Menard,J.

AU - Menon,M.

AU - Meyer,H.

AU - Mikkelsen,D.

AU - Miloshevsky,G.

AU - Mueller,D.

AU - Munsat,T.

AU - Myra,J.

AU - Nelson,B.

AU - Nishino,N.

AU - Nygren,R.

AU - Ono,M.

AU - Osborne,T.

AU - Park,H.

AU - Park,J.

AU - Park,Y. S.

AU - Paul,S.

AU - Peebles,W.

AU - Penaflor,B.

AU - Perkins,R. J.

AU - Phillips,C.

AU - Pigarov,A.

AU - Podesta,M.

AU - Preinhaelter,J.

AU - Raman,R.

AU - Ren,Y.

AU - Rewoldt,G.

AU - Rognlien,T.

AU - Ross,P.

AU - Rowley,C.

AU - Ruskov,E.

AU - Russell,D.

AU - Ruzic,D.

AU - Ryan,P.

AU - Schaffer,M.

AU - Schuster,E.

AU - Scotti,F.

AU - Shaing,K.

AU - Shevchenko,V.

AU - Shinohara,K.

AU - Sizyuk,V.

AU - Skinner,C. H.

AU - Smirnov,A.

AU - Smith,D.

AU - Snyder,P.

AU - Solomon,W.

AU - Sontag,A.

AU - Soukhanovskii,V.

AU - Stoltzfus-Dueck,T.

AU - Stotler,D.

AU - Stratton,B.

AU - Stutman,D.

AU - Takahashi,H.

AU - Takase,Y.

AU - Tamura,N.

AU - Tang,X.

AU - Taylor,G.

AU - Taylor,C.

AU - Tritz,K.

AU - Tsarouhas,D.

AU - Umansky,M.

AU - Urban,J.

AU - Untergberg,E.

AU - Walker,M.

AU - Wampler,W.

AU - Wang,W.

AU - Whaley,J.

AU - White,R.

AU - Wilgen,J.

AU - Wilson,R.

AU - Wong,K. L.

AU - Wright,J.

AU - Xia,Z.

AU - Youchison,D.

AU - Yu,G.

AU - Yuh,H.

AU - Zakharov,L.

AU - Zemlyanov,D.

AU - Zimmer,G.

AU - Zweben,S. J.

PY - 2013/10

Y1 - 2013/10

N2 - Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique ST operational space is leveraged to test physics theories for next-step tokamak operation, including ITER. Present research also examines implications for the coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified for varied wall conditions exhibits a strong improvement of BTτE with decreased electron collisionality, accentuated by lithium (Li) wall conditioning. This result is consistent with nonlinear microtearing simulations that match the experimental electron diffusivity quantitatively and predict reduced electron heat transport at lower collisionality. Beam-emission spectroscopy measurements in the steep gradient region of the pedestal indicate the poloidal correlation length of turbulence of about ten ion gyroradii increases at higher electron density gradient and lower Ti gradient, consistent with turbulence caused by trapped electron instabilities. Density fluctuations in the pedestal top region indicate ion-scale microturbulence compatible with ion temperature gradient and/or kinetic ballooning mode instabilities. Plasma characteristics change nearly continuously with increasing Li evaporation and edge localized modes (ELMs) stabilize due to edge density gradient alteration. Global mode stability studies show stabilizing resonant kinetic effects are enhanced at lower collisionality, but in stark contrast have almost no dependence on collisionality when the plasma is off-resonance. Combined resistive wall mode radial and poloidal field sensor feedback was used to control n = 1 perturbations and improve stability. The disruption probability due to unstable resistive wall modes (RWMs) was surprisingly reduced at very high βN/li > 10 consistent with low frequency magnetohydrodynamic spectroscopy measurements of mode stability. Greater instability seen at intermediate βN is consistent with decreased kinetic RWM stabilization. A model-based RWM state-space controller produced long-pulse discharges exceeding βN = 6.4 and βN/li = 13. Precursor analysis shows 96.3% of disruptions can be predicted with 10 ms warning and a false positive rate of only 2.8%. Disruption halo currents rotate toroidally and can have significant toroidal asymmetry. Global kinks cause measured fast ion redistribution, with full-orbit calculations showing redistribution from the core outward and towards V∥/V = 1 where destabilizing compressional Alfvén eigenmode resonances are expected. Applied 3D fields altered global Alfvén eigenmode characteristics. High-harmonic fast-wave (HHFW) power couples to field lines across the entire width of the scrape-off layer, showing the importance of the inclusion of this phenomenon in designing future RF systems. The snowflake divertor configuration enhanced by radiative detachment showed large reductions in both steady-state and ELM heat fluxes (ELMing peak values down from 19 MW m-2 to less than 1.5 MW m-2). Toroidal asymmetry of heat deposition was observed during ELMs or by 3D fields. The heating power required for accessing H-mode decreased by 30% as the triangularity was decreased by moving the X-point to larger radius, consistent with calculations of the dependence of E × B shear in the edge region on ion heat flux and X-point radius. Co-axial helicity injection reduced the inductive start-up flux, with plasmas ramped to 1 MA requiring 35% less inductive flux. Non-inductive current fraction (NICF) up to 65% is reached experimentally with neutral beam injection at plasma current Ip = 0.7 MA and between 70-100% with HHFW application at Ip = 0.3 MA. NSTX-U scenario development calculations project 100% NICF for a large range of 0.6 < Ip (MA) < 1.35.

AB - Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique ST operational space is leveraged to test physics theories for next-step tokamak operation, including ITER. Present research also examines implications for the coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified for varied wall conditions exhibits a strong improvement of BTτE with decreased electron collisionality, accentuated by lithium (Li) wall conditioning. This result is consistent with nonlinear microtearing simulations that match the experimental electron diffusivity quantitatively and predict reduced electron heat transport at lower collisionality. Beam-emission spectroscopy measurements in the steep gradient region of the pedestal indicate the poloidal correlation length of turbulence of about ten ion gyroradii increases at higher electron density gradient and lower Ti gradient, consistent with turbulence caused by trapped electron instabilities. Density fluctuations in the pedestal top region indicate ion-scale microturbulence compatible with ion temperature gradient and/or kinetic ballooning mode instabilities. Plasma characteristics change nearly continuously with increasing Li evaporation and edge localized modes (ELMs) stabilize due to edge density gradient alteration. Global mode stability studies show stabilizing resonant kinetic effects are enhanced at lower collisionality, but in stark contrast have almost no dependence on collisionality when the plasma is off-resonance. Combined resistive wall mode radial and poloidal field sensor feedback was used to control n = 1 perturbations and improve stability. The disruption probability due to unstable resistive wall modes (RWMs) was surprisingly reduced at very high βN/li > 10 consistent with low frequency magnetohydrodynamic spectroscopy measurements of mode stability. Greater instability seen at intermediate βN is consistent with decreased kinetic RWM stabilization. A model-based RWM state-space controller produced long-pulse discharges exceeding βN = 6.4 and βN/li = 13. Precursor analysis shows 96.3% of disruptions can be predicted with 10 ms warning and a false positive rate of only 2.8%. Disruption halo currents rotate toroidally and can have significant toroidal asymmetry. Global kinks cause measured fast ion redistribution, with full-orbit calculations showing redistribution from the core outward and towards V∥/V = 1 where destabilizing compressional Alfvén eigenmode resonances are expected. Applied 3D fields altered global Alfvén eigenmode characteristics. High-harmonic fast-wave (HHFW) power couples to field lines across the entire width of the scrape-off layer, showing the importance of the inclusion of this phenomenon in designing future RF systems. The snowflake divertor configuration enhanced by radiative detachment showed large reductions in both steady-state and ELM heat fluxes (ELMing peak values down from 19 MW m-2 to less than 1.5 MW m-2). Toroidal asymmetry of heat deposition was observed during ELMs or by 3D fields. The heating power required for accessing H-mode decreased by 30% as the triangularity was decreased by moving the X-point to larger radius, consistent with calculations of the dependence of E × B shear in the edge region on ion heat flux and X-point radius. Co-axial helicity injection reduced the inductive start-up flux, with plasmas ramped to 1 MA requiring 35% less inductive flux. Non-inductive current fraction (NICF) up to 65% is reached experimentally with neutral beam injection at plasma current Ip = 0.7 MA and between 70-100% with HHFW application at Ip = 0.3 MA. NSTX-U scenario development calculations project 100% NICF for a large range of 0.6 < Ip (MA) < 1.35.

UR - http://www.scopus.com/inward/record.url?scp=84884899120&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84884899120&partnerID=8YFLogxK

U2 - 10.1088/0029-5515/53/10/104007

DO - 10.1088/0029-5515/53/10/104007

M3 - Review article

VL - 53

JO - Nuclear Fusion

T2 - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 10

M1 - 104007

ER -