Overview of physics results from NSTX

R. Raman, J. W. Ahn, J. P. Allain, R. Andre, R. Bastasz, D. Battaglia, P. Beiersdorfer, M. Bell, R. Bell, E. Belova, J. Berkery, R. Betti, J. Bialek, T. Bigelow, M. Bitter, J. Boedo, P. Bonoli, A. Boozer, A. Bortolon, D. Brennan & 154 others J. Breslau, R. Buttery, J. Canik, G. Caravelli, C. Chang, N. A. Crocker, D. Darrow, W. 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, B. Hu, 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, S. Krasheninnikov, S. Kubota, H. Kugel, R. La Haye, L. Lao, B. Leblanc, W. Lee, K. Lee, J. Leuer, F. Levinton, Y. Liang, D. Liu, N. Luhmann, R. Maingi, R. Majeski, J. Manickam, D. Mansfield, R. Maqueda, E. Mazzucato, A. McLean, D. McCune, B. McGeehan, G. McKee, S. Medley, 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, S. Paul, W. Peebles, B. Penaflor, C. Phillips, A. Pigarov, M. Podesta, J. Preinhaelter, Y. Ren, H. Reimerdes, G. Rewoldt, P. Ross, C. Rowley, E. Ruskov, D. Russell, D. Ruzic, P. Ryan, S. A. Sabbagh, 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, C. N. Taylor, G. Taylor, C. Taylor, K. Tritz, D. Tsarouhas, M. Umansky, J. Urban, 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: Contribution to journalReview article

Abstract

In the last two experimental campaigns, the low aspect ratio NSTX has explored physics issues critical to both toroidal confinement physics and ITER. Experiments have made extensive use of lithium coatings for wall conditioning, correction of non-axisymmetric field errors and control of n = 1 resistive wall modes (RWMs) to produce high-performance neutral-beam heated discharges extending to 1.7 s in duration with non-inductive current fractions up to 0.7. The RWM control coils have been used to trigger repetitive ELMs with high reliability, and they have also contributed to an improved understanding of both neoclassical tearing mode and RWM stabilization physics, including the interplay between rotation and kinetic effects on stability. High harmonic fast wave (HHFW) heating has produced plasmas with central electron temperatures exceeding 6 keV. The HHFW heating was used to show that there was a 20-40% higher power threshold for the L-H transition for helium than for deuterium plasmas. A new diagnostic showed a depletion of the fast-ion density profile over a broad spatial region as a result of toroidicity-induced Alfvén eigenmodes (TAEs) and energetic-particle modes (EPMs) bursts. In addition, it was observed that other modes (e.g. global Alfvén eigenmodes) can trigger TAE and EPM bursts, suggesting that fast ions are redistributed by high-frequency AEs. The momentum pinch velocity determined by a perturbative technique decreased as the collisionality was reduced, although the pinch to diffusion ratio, Vpinch/χ, remained approximately constant. The mechanisms of deuterium retention by graphite and lithium-coated graphite plasma-facing components have been investigated. To reduce divertor heat flux, a novel divertor configuration, the 'snowflake' divertor, was tested in NSTX and many beneficial aspects were found. A reduction in the required central solenoid flux has been realized in NSTX when discharges initiated by coaxial helicity injection were ramped in current using induction. The resulting plasmas have characteristics needed to meet the objectives of the non-inductive start-up and ramp-up program of NSTX.

Original languageEnglish (US)
Article number094011
JournalNuclear Fusion
Volume51
Issue number9
DOIs
StatePublished - Sep 2011

Fingerprint

physics
energetic particles
bursts
graphite
lithium
actuators
harmonics
heating
deuterium plasma
low aspect ratio
neutral beams
conditioning
solenoids
ramps
deuterium
heat flux
induction
depletion
coils
stabilization

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Raman, R., Ahn, J. W., Allain, J. P., Andre, R., Bastasz, R., Battaglia, D., ... Zweben, S. J. (2011). Overview of physics results from NSTX. Nuclear Fusion, 51(9), [094011]. DOI: 10.1088/0029-5515/51/9/094011

Overview of physics results from NSTX. / Raman, R.; Ahn, J. W.; Allain, J. P.; Andre, R.; Bastasz, R.; Battaglia, D.; Beiersdorfer, P.; Bell, M.; Bell, R.; Belova, E.; Berkery, J.; Betti, R.; Bialek, J.; Bigelow, T.; Bitter, M.; Boedo, J.; Bonoli, P.; Boozer, A.; Bortolon, A.; Brennan, D.; Breslau, J.; Buttery, R.; Canik, J.; Caravelli, G.; Chang, C.; Crocker, N. A.; Darrow, D.; Davis, W.; 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.; Hu, B.; 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.; Krasheninnikov, S.; Kubota, S.; Kugel, H.; La Haye, R.; Lao, L.; Leblanc, B.; Lee, W.; Lee, K.; Leuer, J.; Levinton, F.; Liang, Y.; Liu, D.; Luhmann, N.; Maingi, R.; Majeski, R.; Manickam, J.; Mansfield, D.; Maqueda, R.; Mazzucato, E.; McLean, A.; McCune, D.; McGeehan, B.; McKee, G.; Medley, S.; 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.; Paul, S.; Peebles, W.; Penaflor, B.; Phillips, C.; Pigarov, A.; Podesta, M.; Preinhaelter, J.; Ren, Y.; Reimerdes, H.; Rewoldt, G.; Ross, P.; Rowley, C.; Ruskov, E.; Russell, D.; Ruzic, D.; Ryan, P.; Sabbagh, S. A.; 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, C. N.; Taylor, G.; Taylor, C.; Tritz, K.; Tsarouhas, D.; Umansky, M.; Urban, J.; 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. 51, No. 9, 094011, 09.2011.

Research output: Contribution to journalReview article

Raman, R, Ahn, JW, Allain, JP, Andre, R, Bastasz, R, Battaglia, D, Beiersdorfer, P, Bell, M, Bell, R, Belova, E, Berkery, J, Betti, R, Bialek, J, Bigelow, T, Bitter, M, Boedo, J, Bonoli, P, Boozer, A, Bortolon, A, Brennan, D, Breslau, J, Buttery, R, Canik, J, Caravelli, G, Chang, C, Crocker, NA, Darrow, D, Davis, W, 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, Hu, B, 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, Krasheninnikov, S, Kubota, S, Kugel, H, La Haye, R, Lao, L, Leblanc, B, Lee, W, Lee, K, Leuer, J, Levinton, F, Liang, Y, Liu, D, Luhmann, N, Maingi, R, Majeski, R, Manickam, J, Mansfield, D, Maqueda, R, Mazzucato, E, McLean, A, McCune, D, McGeehan, B, McKee, G, Medley, S, 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, Paul, S, Peebles, W, Penaflor, B, Phillips, C, Pigarov, A, Podesta, M, Preinhaelter, J, Ren, Y, Reimerdes, H, Rewoldt, G, Ross, P, Rowley, C, Ruskov, E, Russell, D, Ruzic, D, Ryan, P, Sabbagh, SA, 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, CN, Taylor, G, Taylor, C, Tritz, K, Tsarouhas, D, Umansky, M, Urban, J, 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 2011, 'Overview of physics results from NSTX' Nuclear Fusion, vol 51, no. 9, 094011. DOI: 10.1088/0029-5515/51/9/094011
Raman R, Ahn JW, Allain JP, Andre R, Bastasz R, Battaglia D et al. Overview of physics results from NSTX. Nuclear Fusion. 2011 Sep;51(9). 094011. Available from, DOI: 10.1088/0029-5515/51/9/094011

Raman, R.; Ahn, J. W.; Allain, J. P.; Andre, R.; Bastasz, R.; Battaglia, D.; Beiersdorfer, P.; Bell, M.; Bell, R.; Belova, E.; Berkery, J.; Betti, R.; Bialek, J.; Bigelow, T.; Bitter, M.; Boedo, J.; Bonoli, P.; Boozer, A.; Bortolon, A.; Brennan, D.; Breslau, J.; Buttery, R.; Canik, J.; Caravelli, G.; Chang, C.; Crocker, N. A.; Darrow, D.; Davis, W.; 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.; Hu, B.; 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.; Krasheninnikov, S.; Kubota, S.; Kugel, H.; La Haye, R.; Lao, L.; Leblanc, B.; Lee, W.; Lee, K.; Leuer, J.; Levinton, F.; Liang, Y.; Liu, D.; Luhmann, N.; Maingi, R.; Majeski, R.; Manickam, J.; Mansfield, D.; Maqueda, R.; Mazzucato, E.; McLean, A.; McCune, D.; McGeehan, B.; McKee, G.; Medley, S.; 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.; Paul, S.; Peebles, W.; Penaflor, B.; Phillips, C.; Pigarov, A.; Podesta, M.; Preinhaelter, J.; Ren, Y.; Reimerdes, H.; Rewoldt, G.; Ross, P.; Rowley, C.; Ruskov, E.; Russell, D.; Ruzic, D.; Ryan, P.; Sabbagh, S. A.; 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, C. N.; Taylor, G.; Taylor, C.; Tritz, K.; Tsarouhas, D.; Umansky, M.; Urban, J.; 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 NSTX.

In: Nuclear Fusion, Vol. 51, No. 9, 094011, 09.2011.

Research output: Contribution to journalReview article

@article{5fd17e2d0d904b6fba7f891fb166d2da,
title = "Overview of physics results from NSTX",
abstract = "In the last two experimental campaigns, the low aspect ratio NSTX has explored physics issues critical to both toroidal confinement physics and ITER. Experiments have made extensive use of lithium coatings for wall conditioning, correction of non-axisymmetric field errors and control of n = 1 resistive wall modes (RWMs) to produce high-performance neutral-beam heated discharges extending to 1.7 s in duration with non-inductive current fractions up to 0.7. The RWM control coils have been used to trigger repetitive ELMs with high reliability, and they have also contributed to an improved understanding of both neoclassical tearing mode and RWM stabilization physics, including the interplay between rotation and kinetic effects on stability. High harmonic fast wave (HHFW) heating has produced plasmas with central electron temperatures exceeding 6 keV. The HHFW heating was used to show that there was a 20-40% higher power threshold for the L-H transition for helium than for deuterium plasmas. A new diagnostic showed a depletion of the fast-ion density profile over a broad spatial region as a result of toroidicity-induced Alfvén eigenmodes (TAEs) and energetic-particle modes (EPMs) bursts. In addition, it was observed that other modes (e.g. global Alfvén eigenmodes) can trigger TAE and EPM bursts, suggesting that fast ions are redistributed by high-frequency AEs. The momentum pinch velocity determined by a perturbative technique decreased as the collisionality was reduced, although the pinch to diffusion ratio, Vpinch/χ, remained approximately constant. The mechanisms of deuterium retention by graphite and lithium-coated graphite plasma-facing components have been investigated. To reduce divertor heat flux, a novel divertor configuration, the 'snowflake' divertor, was tested in NSTX and many beneficial aspects were found. A reduction in the required central solenoid flux has been realized in NSTX when discharges initiated by coaxial helicity injection were ramped in current using induction. The resulting plasmas have characteristics needed to meet the objectives of the non-inductive start-up and ramp-up program of NSTX.",
author = "R. Raman and Ahn, {J. W.} and Allain, {J. P.} and R. Andre and R. Bastasz and D. Battaglia and P. Beiersdorfer and M. Bell and R. Bell 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. Brennan and J. Breslau and R. Buttery and J. Canik and G. Caravelli and C. Chang and Crocker, {N. A.} and D. Darrow and W. 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 B. Hu 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 S. Krasheninnikov and S. Kubota and H. Kugel and {La Haye}, R. 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 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 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 S. Paul and W. Peebles and B. Penaflor and C. Phillips and A. Pigarov and M. Podesta and J. Preinhaelter and Y. Ren and H. Reimerdes and G. Rewoldt and P. Ross and C. Rowley and E. Ruskov and D. Russell and D. Ruzic and P. Ryan and Sabbagh, {S. A.} 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 Taylor, {C. N.} and G. Taylor and C. Taylor and K. Tritz and D. Tsarouhas and M. Umansky and J. Urban 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 = "2011",
month = "9",
doi = "10.1088/0029-5515/51/9/094011",
volume = "51",
journal = "Nuclear Fusion",
issn = "0029-5515",
publisher = "IOP Publishing Ltd.",
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}

TY - JOUR

T1 - Overview of physics results from NSTX

AU - Raman,R.

AU - Ahn,J. W.

AU - Allain,J. P.

AU - Andre,R.

AU - Bastasz,R.

AU - Battaglia,D.

AU - Beiersdorfer,P.

AU - Bell,M.

AU - Bell,R.

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 - Brennan,D.

AU - Breslau,J.

AU - Buttery,R.

AU - Canik,J.

AU - Caravelli,G.

AU - Chang,C.

AU - Crocker,N. A.

AU - Darrow,D.

AU - Davis,W.

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 - Hu,B.

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 - Krasheninnikov,S.

AU - Kubota,S.

AU - Kugel,H.

AU - La Haye,R.

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 - 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 - 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 - Paul,S.

AU - Peebles,W.

AU - Penaflor,B.

AU - Phillips,C.

AU - Pigarov,A.

AU - Podesta,M.

AU - Preinhaelter,J.

AU - Ren,Y.

AU - Reimerdes,H.

AU - Rewoldt,G.

AU - Ross,P.

AU - Rowley,C.

AU - Ruskov,E.

AU - Russell,D.

AU - Ruzic,D.

AU - Ryan,P.

AU - Sabbagh,S. A.

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,C. N.

AU - Taylor,G.

AU - Taylor,C.

AU - Tritz,K.

AU - Tsarouhas,D.

AU - Umansky,M.

AU - Urban,J.

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 - 2011/9

Y1 - 2011/9

N2 - In the last two experimental campaigns, the low aspect ratio NSTX has explored physics issues critical to both toroidal confinement physics and ITER. Experiments have made extensive use of lithium coatings for wall conditioning, correction of non-axisymmetric field errors and control of n = 1 resistive wall modes (RWMs) to produce high-performance neutral-beam heated discharges extending to 1.7 s in duration with non-inductive current fractions up to 0.7. The RWM control coils have been used to trigger repetitive ELMs with high reliability, and they have also contributed to an improved understanding of both neoclassical tearing mode and RWM stabilization physics, including the interplay between rotation and kinetic effects on stability. High harmonic fast wave (HHFW) heating has produced plasmas with central electron temperatures exceeding 6 keV. The HHFW heating was used to show that there was a 20-40% higher power threshold for the L-H transition for helium than for deuterium plasmas. A new diagnostic showed a depletion of the fast-ion density profile over a broad spatial region as a result of toroidicity-induced Alfvén eigenmodes (TAEs) and energetic-particle modes (EPMs) bursts. In addition, it was observed that other modes (e.g. global Alfvén eigenmodes) can trigger TAE and EPM bursts, suggesting that fast ions are redistributed by high-frequency AEs. The momentum pinch velocity determined by a perturbative technique decreased as the collisionality was reduced, although the pinch to diffusion ratio, Vpinch/χ, remained approximately constant. The mechanisms of deuterium retention by graphite and lithium-coated graphite plasma-facing components have been investigated. To reduce divertor heat flux, a novel divertor configuration, the 'snowflake' divertor, was tested in NSTX and many beneficial aspects were found. A reduction in the required central solenoid flux has been realized in NSTX when discharges initiated by coaxial helicity injection were ramped in current using induction. The resulting plasmas have characteristics needed to meet the objectives of the non-inductive start-up and ramp-up program of NSTX.

AB - In the last two experimental campaigns, the low aspect ratio NSTX has explored physics issues critical to both toroidal confinement physics and ITER. Experiments have made extensive use of lithium coatings for wall conditioning, correction of non-axisymmetric field errors and control of n = 1 resistive wall modes (RWMs) to produce high-performance neutral-beam heated discharges extending to 1.7 s in duration with non-inductive current fractions up to 0.7. The RWM control coils have been used to trigger repetitive ELMs with high reliability, and they have also contributed to an improved understanding of both neoclassical tearing mode and RWM stabilization physics, including the interplay between rotation and kinetic effects on stability. High harmonic fast wave (HHFW) heating has produced plasmas with central electron temperatures exceeding 6 keV. The HHFW heating was used to show that there was a 20-40% higher power threshold for the L-H transition for helium than for deuterium plasmas. A new diagnostic showed a depletion of the fast-ion density profile over a broad spatial region as a result of toroidicity-induced Alfvén eigenmodes (TAEs) and energetic-particle modes (EPMs) bursts. In addition, it was observed that other modes (e.g. global Alfvén eigenmodes) can trigger TAE and EPM bursts, suggesting that fast ions are redistributed by high-frequency AEs. The momentum pinch velocity determined by a perturbative technique decreased as the collisionality was reduced, although the pinch to diffusion ratio, Vpinch/χ, remained approximately constant. The mechanisms of deuterium retention by graphite and lithium-coated graphite plasma-facing components have been investigated. To reduce divertor heat flux, a novel divertor configuration, the 'snowflake' divertor, was tested in NSTX and many beneficial aspects were found. A reduction in the required central solenoid flux has been realized in NSTX when discharges initiated by coaxial helicity injection were ramped in current using induction. The resulting plasmas have characteristics needed to meet the objectives of the non-inductive start-up and ramp-up program of NSTX.

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U2 - 10.1088/0029-5515/51/9/094011

DO - 10.1088/0029-5515/51/9/094011

M3 - Review article

VL - 51

JO - Nuclear Fusion

T2 - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 9

M1 - 094011

ER -