PPPL-3709 is available in <a href="PPPL-3709.pdf">pdf</a> format (936 KB).

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<b>Results of NSTX Heating Experiments</b>
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<b>Authors:</b> D. Mueller, M. Ono, M.G. Bell, R.E. Bell, M. Bitter, C. Bourdelle, D.S. Darrow, P.C. Efthimion, E.D. Fredrickson, D.A. Gates, R.J. Goldston, L.R. Grisham, R.J. Hawryluk, K.W. Hill, J.C. Hosea, S.C. Jardin, H. Ji, S.M. Kaye, R. Kaita, H.W. Kugel, D.W. Johnson, B.P. LeBlanc, R. Majeski, E. Mazzucato, S.S. Medley, J.E. Menard, H.K. Park, S.F. Paul, C.K. Phillips, M.H. Redi, A.L. Rosenberg, C.H. Skinner, V.A. Soukhanovskii, B. Stratton, E.J. Synakowski, G. Taylor, J.R. Wilson, S.J. Zweben, Y-K.M. Peng, R. Barry, T. Bigelow, C.E. Bush, M. Carter, R. Maingi, M. Menon, P.M. Ryan, D.W. Swain, J. Wilgen and 37 additional authors

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<b>Date of PPPL Report:</b> June 2002
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<b>Published in:</b> IEEE Transactions of Plasma Science <b> 31</b> No. 1 (February 2003)  60-67</p>


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The National Spherical Torus Experiment (NSTX) at Princeton is designed to assess the potential of the low-aspect-ratio spherical torus concept for magnetic plasma confinement.  The plasma has been heated by up to 5 MW of neutral beam injection, NBI, at an injection energy of 90 keV and up to 6 MW of high harmonic fast wave, HHFW, at 30 MHz. NSTX has achieved beta<sub>T</sub> of 32&#37;. A variety of MHD phenomena have been observed to limit beta.  NSTX has now begun addressing <font face ="symbol">t</font><sub>E</sub> scaling, beta limits and current drive issues.  During the NBI heating experiments, a broad T<sub>i</sub> profile with T<sub>i</sub> up to 2 keV, T<sub>i</sub> > T<sub>e</sub> and a large toroidal rotation.  Transport analysis suggests that the impurity ions have diffusivities approaching neoclassical.  For L-Mode plasmas, <font face ="symbol">t</font><sub>E</sub> is up to two times the ITER-89P L-Mode scaling and exceeds the ITER-98pby2 H-Mode scaling in some cases.  Transitions to H-Mode have been observed which result in an approximate doubling of <font face ="symbol">t</font><sub>E</sub>. after the transition in some conditions.  During HHFW heating, T<sub>e</sub> > T<sub>i</sub> and T<sub>e</sub> up to 3.5 keV were observed. Current drive has been studied using coaxial helicity injection (CHI), which has produced 390 kA of toroidal current and HHFW, which has produced H-modes with significant bootstrap current fraction at low I<sub>p</sub>, high q and high beta<sub>p</sub>.





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