Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX)

S. M. Kaye, M. G. Bell, R. E. Bell, S. Bernabei, J. Bialek, T. Biewer, W. Blanchard, J. Boedo, C. Bush, M. D. Carter, W. Choe, N. Crocker, D. S. Darrow, W. Davis, L. Delgado-Aparicio, S. Diem, J. Ferron, A. Field, J. Foley, E. D. FredricksonD. A. Gates, T. Gibney, R. Harvey, R. E. Hatcher, W. Heidbrink, K. Hill, J. C. Hosea, T. R. Jarboe, D. W. Johnson, R. Kaita, C. Kessel, S. Kubota, H. W. Kugel, J. Lawson, B. P. le Blanc, K. C. Lee, F. Levinton, R. Maingi, J. Manickam, R. Maqueda, R. Marsala, D. Mastrovito, T. K. Mau, S. S. Medley, J. Menard, H. Meyer, D. R. Mikkelsen, D. Mueller, T. Munsat, B. A. Nelson, C. Neumeyer, N. Nishino, M. Ono, H. Park, W. Park, S. Paul, T. Peebles, M. Peng, C. Phillips, A. Pigarov, R. Pinsker, A. Ram, S. Ramakrishnan, R. Raman, D. Rasmussen, M. Redi, M. Rensink, G. Rewoldt, J. Robinson, P. Roney, A. L. Roquemore, E. Ruskov, P. Ryan, S. A. Sabbagh, H. Schneider, C. H. Skinner, D. R. Smith, A. Sontag, V. Soukhanovskii, T. Stevenson, D. Stotler, B. Stratton, D. Stutman, D. Swain, E. Synakowski, Y. Takase, G. Taylor, K. Tritz, A. von Halle, M. Wade, R. White, J. Wilgen, M. Williams, J. R. Wilson, W. Zhu, S. J. Zweben, R. Akers, P. Beiersdorfer, R. Betti, T. Bigelow, M. Bitter, P. Bonoli, C. Bourdelle, C. S. Chang, J. Chrzanowski, C. Domier, L. Dudek, P. C. Efthimion, M. Finkenthal, E. Fredd, G. Y. Fu, A. Glasser, R. J. Goldston, N. L. Greenough, L. R. Grisham, N. Gorelenkov, L. Guazzotto, R. J. Hawryluk, J. Hogan, W. Houlberg, D. Humphreys, F. Jaeger, M. Kalish, S. Krasheninnikov, L. L. Lao, J. Lawrence, J. Leuer, D. Liu, N. C. Luhmann, E. Mazzucato, G. Oliaro, D. Pacella, R. Parsells, M. Schaffer, I. Semenov, Ker-Chung Shaing, M. A. Shapiro, K. Shinohara, P. Sichta, X. Tang, R. Vero, D. Walker, W. Wampler

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modelling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high βT (up to ∼40%) lasting for many energy confinement times. βT can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefitted greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a BT dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60% of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfvén eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fuelling and power and particle control.

Original languageEnglish
JournalNuclear Fusion
Volume45
Issue number10
DOIs
Publication statusPublished - 2005 Oct 1

Fingerprint

plasma currents
elongation
aspect ratio
harmonics
low aspect ratio
physics
plasma control
refueling
beam injection
neutral beams
energetic particles
installing
ions
coils
spatial resolution
transport properties
turbulence
injection
shear
scaling

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Kaye, S. M., Bell, M. G., Bell, R. E., Bernabei, S., Bialek, J., Biewer, T., ... Wampler, W. (2005). Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX). Nuclear Fusion, 45(10). https://doi.org/10.1088/0029-5515/45/10/S14
Kaye, S. M. ; Bell, M. G. ; Bell, R. E. ; Bernabei, S. ; Bialek, J. ; Biewer, T. ; Blanchard, W. ; Boedo, J. ; Bush, C. ; Carter, M. D. ; Choe, W. ; Crocker, N. ; Darrow, D. S. ; Davis, W. ; Delgado-Aparicio, L. ; Diem, S. ; Ferron, J. ; Field, A. ; Foley, J. ; Fredrickson, E. D. ; Gates, D. A. ; Gibney, T. ; Harvey, R. ; Hatcher, R. E. ; Heidbrink, W. ; Hill, K. ; Hosea, J. C. ; Jarboe, T. R. ; Johnson, D. W. ; Kaita, R. ; Kessel, C. ; Kubota, S. ; Kugel, H. W. ; Lawson, J. ; le Blanc, B. P. ; Lee, K. C. ; Levinton, F. ; Maingi, R. ; Manickam, J. ; Maqueda, R. ; Marsala, R. ; Mastrovito, D. ; Mau, T. K. ; Medley, S. S. ; Menard, J. ; Meyer, H. ; Mikkelsen, D. R. ; Mueller, D. ; Munsat, T. ; Nelson, B. A. ; Neumeyer, C. ; Nishino, N. ; Ono, M. ; Park, H. ; Park, W. ; Paul, S. ; Peebles, T. ; Peng, M. ; Phillips, C. ; Pigarov, A. ; Pinsker, R. ; Ram, A. ; Ramakrishnan, S. ; Raman, R. ; Rasmussen, D. ; Redi, M. ; Rensink, M. ; Rewoldt, G. ; Robinson, J. ; Roney, P. ; Roquemore, A. L. ; Ruskov, E. ; Ryan, P. ; Sabbagh, S. A. ; Schneider, H. ; Skinner, C. H. ; Smith, D. R. ; Sontag, A. ; Soukhanovskii, V. ; Stevenson, T. ; Stotler, D. ; Stratton, B. ; Stutman, D. ; Swain, D. ; Synakowski, E. ; Takase, Y. ; Taylor, G. ; Tritz, K. ; von Halle, A. ; Wade, M. ; White, R. ; Wilgen, J. ; Williams, M. ; Wilson, J. R. ; Zhu, W. ; Zweben, S. J. ; Akers, R. ; Beiersdorfer, P. ; Betti, R. ; Bigelow, T. ; Bitter, M. ; Bonoli, P. ; Bourdelle, C. ; Chang, C. S. ; Chrzanowski, J. ; Domier, C. ; Dudek, L. ; Efthimion, P. C. ; Finkenthal, M. ; Fredd, E. ; Fu, G. Y. ; Glasser, A. ; Goldston, R. J. ; Greenough, N. L. ; Grisham, L. R. ; Gorelenkov, N. ; Guazzotto, L. ; Hawryluk, R. J. ; Hogan, J. ; Houlberg, W. ; Humphreys, D. ; Jaeger, F. ; Kalish, M. ; Krasheninnikov, S. ; Lao, L. L. ; Lawrence, J. ; Leuer, J. ; Liu, D. ; Luhmann, N. C. ; Mazzucato, E. ; Oliaro, G. ; Pacella, D. ; Parsells, R. ; Schaffer, M. ; Semenov, I. ; Shaing, Ker-Chung ; Shapiro, M. A. ; Shinohara, K. ; Sichta, P. ; Tang, X. ; Vero, R. ; Walker, D. ; Wampler, W. / Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX). In: Nuclear Fusion. 2005 ; Vol. 45, No. 10.
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title = "Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX)",
abstract = "The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modelling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high βT (up to ∼40{\%}) lasting for many energy confinement times. βT can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefitted greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a BT dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60{\%} of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfv{\'e}n eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fuelling and power and particle control.",
author = "Kaye, {S. M.} and Bell, {M. G.} and Bell, {R. E.} and S. Bernabei and J. Bialek and T. Biewer and W. Blanchard and J. Boedo and C. Bush and Carter, {M. D.} and W. Choe and N. Crocker and Darrow, {D. S.} and W. Davis and L. Delgado-Aparicio and S. Diem and J. Ferron and A. Field and J. Foley and Fredrickson, {E. D.} and Gates, {D. A.} and T. Gibney and R. Harvey and Hatcher, {R. E.} and W. Heidbrink and K. Hill and Hosea, {J. C.} and Jarboe, {T. R.} and Johnson, {D. W.} and R. Kaita and C. Kessel and S. Kubota and Kugel, {H. W.} and J. Lawson and {le Blanc}, {B. P.} and Lee, {K. C.} and F. Levinton and R. Maingi and J. Manickam and R. Maqueda and R. Marsala and D. Mastrovito and Mau, {T. K.} and Medley, {S. S.} and J. Menard and H. Meyer and Mikkelsen, {D. R.} and D. Mueller and T. Munsat and Nelson, {B. A.} and C. Neumeyer and N. Nishino and M. Ono and H. Park and W. Park and S. Paul and T. Peebles and M. Peng and C. Phillips and A. Pigarov and R. Pinsker and A. Ram and S. Ramakrishnan and R. Raman and D. Rasmussen and M. Redi and M. Rensink and G. Rewoldt and J. Robinson and P. Roney and Roquemore, {A. L.} and E. Ruskov and P. Ryan and Sabbagh, {S. A.} and H. Schneider and Skinner, {C. H.} and Smith, {D. R.} and A. Sontag and V. Soukhanovskii and T. Stevenson and D. Stotler and B. Stratton and D. Stutman and D. Swain and E. Synakowski and Y. Takase and G. Taylor and K. Tritz and {von Halle}, A. and M. Wade and R. White and J. Wilgen and M. Williams and Wilson, {J. R.} and W. Zhu and Zweben, {S. J.} and R. Akers and P. Beiersdorfer and R. Betti and T. Bigelow and M. Bitter and P. Bonoli and C. Bourdelle and Chang, {C. S.} and J. Chrzanowski and C. Domier and L. Dudek and Efthimion, {P. C.} and M. Finkenthal and E. Fredd and Fu, {G. Y.} and A. Glasser and Goldston, {R. J.} and Greenough, {N. L.} and Grisham, {L. R.} and N. Gorelenkov and L. Guazzotto and Hawryluk, {R. J.} and J. Hogan and W. Houlberg and D. Humphreys and F. Jaeger and M. Kalish and S. Krasheninnikov and Lao, {L. L.} and J. Lawrence and J. Leuer and D. Liu and Luhmann, {N. C.} and E. Mazzucato and G. Oliaro and D. Pacella and R. Parsells and M. Schaffer and I. Semenov and Ker-Chung Shaing and Shapiro, {M. A.} and K. Shinohara and P. Sichta and X. Tang and R. Vero and D. Walker and W. Wampler",
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language = "English",
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journal = "Nuclear Fusion",
issn = "0029-5515",
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Kaye, SM, Bell, MG, Bell, RE, Bernabei, S, Bialek, J, Biewer, T, Blanchard, W, Boedo, J, Bush, C, Carter, MD, Choe, W, Crocker, N, Darrow, DS, Davis, W, Delgado-Aparicio, L, Diem, S, Ferron, J, Field, A, Foley, J, Fredrickson, ED, Gates, DA, Gibney, T, Harvey, R, Hatcher, RE, Heidbrink, W, Hill, K, Hosea, JC, Jarboe, TR, Johnson, DW, Kaita, R, Kessel, C, Kubota, S, Kugel, HW, Lawson, J, le Blanc, BP, Lee, KC, Levinton, F, Maingi, R, Manickam, J, Maqueda, R, Marsala, R, Mastrovito, D, Mau, TK, Medley, SS, Menard, J, Meyer, H, Mikkelsen, DR, Mueller, D, Munsat, T, Nelson, BA, Neumeyer, C, Nishino, N, Ono, M, Park, H, Park, W, Paul, S, Peebles, T, Peng, M, Phillips, C, Pigarov, A, Pinsker, R, Ram, A, Ramakrishnan, S, Raman, R, Rasmussen, D, Redi, M, Rensink, M, Rewoldt, G, Robinson, J, Roney, P, Roquemore, AL, Ruskov, E, Ryan, P, Sabbagh, SA, Schneider, H, Skinner, CH, Smith, DR, Sontag, A, Soukhanovskii, V, Stevenson, T, Stotler, D, Stratton, B, Stutman, D, Swain, D, Synakowski, E, Takase, Y, Taylor, G, Tritz, K, von Halle, A, Wade, M, White, R, Wilgen, J, Williams, M, Wilson, JR, Zhu, W, Zweben, SJ, Akers, R, Beiersdorfer, P, Betti, R, Bigelow, T, Bitter, M, Bonoli, P, Bourdelle, C, Chang, CS, Chrzanowski, J, Domier, C, Dudek, L, Efthimion, PC, Finkenthal, M, Fredd, E, Fu, GY, Glasser, A, Goldston, RJ, Greenough, NL, Grisham, LR, Gorelenkov, N, Guazzotto, L, Hawryluk, RJ, Hogan, J, Houlberg, W, Humphreys, D, Jaeger, F, Kalish, M, Krasheninnikov, S, Lao, LL, Lawrence, J, Leuer, J, Liu, D, Luhmann, NC, Mazzucato, E, Oliaro, G, Pacella, D, Parsells, R, Schaffer, M, Semenov, I, Shaing, K-C, Shapiro, MA, Shinohara, K, Sichta, P, Tang, X, Vero, R, Walker, D & Wampler, W 2005, 'Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX)', Nuclear Fusion, vol. 45, no. 10. https://doi.org/10.1088/0029-5515/45/10/S14

Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX). / Kaye, S. M.; Bell, M. G.; Bell, R. E.; Bernabei, S.; Bialek, J.; Biewer, T.; Blanchard, W.; Boedo, J.; Bush, C.; Carter, M. D.; Choe, W.; Crocker, N.; Darrow, D. S.; Davis, W.; Delgado-Aparicio, L.; Diem, S.; Ferron, J.; Field, A.; Foley, J.; Fredrickson, E. D.; Gates, D. A.; Gibney, T.; Harvey, R.; Hatcher, R. E.; Heidbrink, W.; Hill, K.; Hosea, J. C.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kessel, C.; Kubota, S.; Kugel, H. W.; Lawson, J.; le Blanc, B. P.; Lee, K. C.; Levinton, F.; Maingi, R.; Manickam, J.; Maqueda, R.; Marsala, R.; Mastrovito, D.; Mau, T. K.; Medley, S. S.; Menard, J.; Meyer, H.; Mikkelsen, D. R.; Mueller, D.; Munsat, T.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ono, M.; Park, H.; Park, W.; Paul, S.; Peebles, T.; Peng, M.; Phillips, C.; Pigarov, A.; Pinsker, R.; Ram, A.; Ramakrishnan, S.; Raman, R.; Rasmussen, D.; Redi, M.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Roquemore, A. L.; Ruskov, E.; Ryan, P.; Sabbagh, S. A.; Schneider, H.; Skinner, C. H.; Smith, D. R.; Sontag, A.; Soukhanovskii, V.; Stevenson, T.; Stotler, D.; Stratton, B.; Stutman, D.; Swain, D.; Synakowski, E.; Takase, Y.; Taylor, G.; Tritz, K.; von Halle, A.; Wade, M.; White, R.; Wilgen, J.; Williams, M.; Wilson, J. R.; Zhu, W.; Zweben, S. J.; Akers, R.; Beiersdorfer, P.; Betti, R.; Bigelow, T.; Bitter, M.; Bonoli, P.; Bourdelle, C.; Chang, C. S.; Chrzanowski, J.; Domier, C.; Dudek, L.; Efthimion, P. C.; Finkenthal, M.; Fredd, E.; Fu, G. Y.; Glasser, A.; Goldston, R. J.; Greenough, N. L.; Grisham, L. R.; Gorelenkov, N.; Guazzotto, L.; Hawryluk, R. J.; Hogan, J.; Houlberg, W.; Humphreys, D.; Jaeger, F.; Kalish, M.; Krasheninnikov, S.; Lao, L. L.; Lawrence, J.; Leuer, J.; Liu, D.; Luhmann, N. C.; Mazzucato, E.; Oliaro, G.; Pacella, D.; Parsells, R.; Schaffer, M.; Semenov, I.; Shaing, Ker-Chung; Shapiro, M. A.; Shinohara, K.; Sichta, P.; Tang, X.; Vero, R.; Walker, D.; Wampler, W.

In: Nuclear Fusion, Vol. 45, No. 10, 01.10.2005.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX)

AU - Kaye, S. M.

AU - Bell, M. G.

AU - Bell, R. E.

AU - Bernabei, S.

AU - Bialek, J.

AU - Biewer, T.

AU - Blanchard, W.

AU - Boedo, J.

AU - Bush, C.

AU - Carter, M. D.

AU - Choe, W.

AU - Crocker, N.

AU - Darrow, D. S.

AU - Davis, W.

AU - Delgado-Aparicio, L.

AU - Diem, S.

AU - Ferron, J.

AU - Field, A.

AU - Foley, J.

AU - Fredrickson, E. D.

AU - Gates, D. A.

AU - Gibney, T.

AU - Harvey, R.

AU - Hatcher, R. E.

AU - Heidbrink, W.

AU - Hill, K.

AU - Hosea, J. C.

AU - Jarboe, T. R.

AU - Johnson, D. W.

AU - Kaita, R.

AU - Kessel, C.

AU - Kubota, S.

AU - Kugel, H. W.

AU - Lawson, J.

AU - le Blanc, B. P.

AU - Lee, K. C.

AU - Levinton, F.

AU - Maingi, R.

AU - Manickam, J.

AU - Maqueda, R.

AU - Marsala, R.

AU - Mastrovito, D.

AU - Mau, T. K.

AU - Medley, S. S.

AU - Menard, J.

AU - Meyer, H.

AU - Mikkelsen, D. R.

AU - Mueller, D.

AU - Munsat, T.

AU - Nelson, B. A.

AU - Neumeyer, C.

AU - Nishino, N.

AU - Ono, M.

AU - Park, H.

AU - Park, W.

AU - Paul, S.

AU - Peebles, T.

AU - Peng, M.

AU - Phillips, C.

AU - Pigarov, A.

AU - Pinsker, R.

AU - Ram, A.

AU - Ramakrishnan, S.

AU - Raman, R.

AU - Rasmussen, D.

AU - Redi, M.

AU - Rensink, M.

AU - Rewoldt, G.

AU - Robinson, J.

AU - Roney, P.

AU - Roquemore, A. L.

AU - Ruskov, E.

AU - Ryan, P.

AU - Sabbagh, S. A.

AU - Schneider, H.

AU - Skinner, C. H.

AU - Smith, D. R.

AU - Sontag, A.

AU - Soukhanovskii, V.

AU - Stevenson, T.

AU - Stotler, D.

AU - Stratton, B.

AU - Stutman, D.

AU - Swain, D.

AU - Synakowski, E.

AU - Takase, Y.

AU - Taylor, G.

AU - Tritz, K.

AU - von Halle, A.

AU - Wade, M.

AU - White, R.

AU - Wilgen, J.

AU - Williams, M.

AU - Wilson, J. R.

AU - Zhu, W.

AU - Zweben, S. J.

AU - Akers, R.

AU - Beiersdorfer, P.

AU - Betti, R.

AU - Bigelow, T.

AU - Bitter, M.

AU - Bonoli, P.

AU - Bourdelle, C.

AU - Chang, C. S.

AU - Chrzanowski, J.

AU - Domier, C.

AU - Dudek, L.

AU - Efthimion, P. C.

AU - Finkenthal, M.

AU - Fredd, E.

AU - Fu, G. Y.

AU - Glasser, A.

AU - Goldston, R. J.

AU - Greenough, N. L.

AU - Grisham, L. R.

AU - Gorelenkov, N.

AU - Guazzotto, L.

AU - Hawryluk, R. J.

AU - Hogan, J.

AU - Houlberg, W.

AU - Humphreys, D.

AU - Jaeger, F.

AU - Kalish, M.

AU - Krasheninnikov, S.

AU - Lao, L. L.

AU - Lawrence, J.

AU - Leuer, J.

AU - Liu, D.

AU - Luhmann, N. C.

AU - Mazzucato, E.

AU - Oliaro, G.

AU - Pacella, D.

AU - Parsells, R.

AU - Schaffer, M.

AU - Semenov, I.

AU - Shaing, Ker-Chung

AU - Shapiro, M. A.

AU - Shinohara, K.

AU - Sichta, P.

AU - Tang, X.

AU - Vero, R.

AU - Walker, D.

AU - Wampler, W.

PY - 2005/10/1

Y1 - 2005/10/1

N2 - The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modelling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high βT (up to ∼40%) lasting for many energy confinement times. βT can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefitted greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a BT dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60% of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfvén eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fuelling and power and particle control.

AB - The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modelling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high βT (up to ∼40%) lasting for many energy confinement times. βT can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefitted greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a BT dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60% of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfvén eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fuelling and power and particle control.

UR - http://www.scopus.com/inward/record.url?scp=26844521677&partnerID=8YFLogxK

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U2 - 10.1088/0029-5515/45/10/S14

DO - 10.1088/0029-5515/45/10/S14

M3 - Article

AN - SCOPUS:26844521677

VL - 45

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 10

ER -