Current Control in ITER Steady State Plasmas With Neutral Beam Steering
Authors: R.V. Budny
Abstract:
Predictions of quasi steady state DT plasmas in ITER [R. Aymar et al., Nucl. Fusion 41, 1301 2001] are generated using the PTRANSP code [R. V. Budny, Nucl. Fusion 49, 085008 2009]. The plasma temperatures, densities, boundary shape, and total current (9 - 10 MA) anticipated for ITER steady state plasmas are specified. Current drive by negative ion neutral beam injection, lowerhybrid, and electron cyclotron resonance are calculated. Four modes of operation with different combinations of current drive are studied. For each mode, scans with the NNBI aimed at differing heights in the plasma are performed to study their effects on current control on the q profile. The time-evolution of the currents and q are calculated, and long-duration transients (up to ≃ 1500 s) are predicted. Effects of the beam and alpha ion pressures on the MHD equilibrium are predicted to significantly alter the bootstrap current. The TEQ equilibrium solver [L. Degtyarev, and V. Drozdov, Computer Physics Reports 46, 481 (1985)] in PTRANSP is found to be much more accurate than the VMEC solver [S. P. Hirshman, U. Schwena, and J. Nuhrenberg, J. Comput. Phys. 87 396 (1990)]. Quasi steady state, strongly reversed q profiles are predicted for some beam injection angles when the current drive and bootstrap currents are sufficiently large.
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Submitted to: Physics of Plasmas (Feb 2010)
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Download PPPL-4440 (pdf 2.89MB 24 pp)
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