Scenario Development During Commissioning Operations on the National Spherical Torus Experiment Upgrade

Battaglia, D. J. ; Boyer, M. D. ; Gerhardt, S. ; Mueller, D. ; Myers, C. E. ; Guttenfelder, W. ; Menard, J. E. ; Sabbagh, S. A.; Scotti, F.; Bedoya, F.; Bell, R. E. ; Berkery, J. W. ; Diallo, A. ; Ferraro, N. ; Jaworski, M. A. ; Kaye, S. M. ; LeBlanc, B. P. ; Ono, M. ; Park, J. -K. ; Podesta, M. ; Raman, R.; Soukhanovskii, V.
Issue date: 2018
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Battaglia, D. J., Boyer, M. D., Gerhardt, S., Mueller, D., Myers, C. E., Guttenfelder, W., Menard, J. E., Sabbagh, S. A., Scotti, F., Bedoya, F., Bell, R. E., Berkery, J. W., Diallo, A., Ferraro, N., Jaworski, M. A., Kaye, S. M., LeBlanc, B. P., Ono, M., Park, J. -K., Podesta, M., Raman, R., & Soukhanovskii, V. (2018). Scenario Development During Commissioning Operations on the National Spherical Torus Experiment Upgrade [Data set]. Princeton Plasma Physics Laboratory, Princeton University.
  author      = {Battaglia, D. J. and
                Boyer, M. D. and
                Gerhardt, S. and
                Mueller, D. and
                Myers, C. E. and
                Guttenfelder, W. and
                Menard, J. E. and
                Sabbagh, S. A. and
                Scotti, F. and
                Bedoya, F. and
                Bell, R. E. and
                Berkery, J. W. and
                Diallo, A. and
                Ferraro, N. and
                Jaworski, M. A. and
                Kaye, S. M. and
                LeBlanc, B. P. and
                Ono, M. and
                Park, J. -K. and
                Podesta, M. and
                Raman, R. and
                Soukhanovskii, V.},
  title       = {{Scenario Development During Commissionin
                g Operations on the National Spherical T
                orus Experiment Upgrade}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2018,
  url         = {}

The National Spherical Torus Experiment Upgrade (NSTX-U) will advance the physics basis required for achieving steady-state, high-beta, and high-confinement conditions in a tokamak by accessing high toroidal field (1 T) and plasma current (1.0 - 2.0 MA) in a low aspect ratio geometry (A = 1.6 - 1.8) with flexible auxiliary heating systems (12 MW NBI, 6 MW HHFW). This paper describes progress in the development of L- and H-mode discharge scenarios and the commissioning of operational tools in the first ten weeks of operation that enable the scientific mission of NSTX-U. Vacuum field calculations completed prior to operations supported the rapid development and optimization of inductive breakdown at different values of ohmic solenoid current. The toroidal magnetic field (B_T0 = 0.65 T) exceeded the maximum values achieved on NSTX and novel long-pulse L-mode discharges with regular sawtooth activity exceeded the longest pulses produced on NSTX (tpulse > 1.8s). The increased flux of the central solenoid facilitated the development of stationary L-mode discharges over a range of density and plasma current (Ip). H-mode discharges achieved similar levels of stored energy, confinement (H98y,2 > 1) and stability (beta_N/beta_N-nowall > 1) compared to NSTX discharges for Ip < 1 MA. High-performance H-mode scenarios require an L-H transition early in the Ip ramp-up phase in order to obtain low internal inductance (li) throughout the discharge, which is conducive to maintaining vertical stability at high elongation (kappa > 2.2) and achieving long periods of MHD quiescent operations. The rapid progress in developing L- and H-mode scenarios in support of the scientific program was enabled by advances in real-time plasma control, efficient error field identification and correction, effective conditioning of the graphite wall and excellent diagnostic availability.

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