Ideal MHD Stability and Performance of ITER Steady State Scenarios With ITBs
Authors: F.M. Poli, C.E. Kessel, M.S. Chance, S.C. Jardin and J. Manickam
Abstract: Non-inductive steady state scenarios on ITER will need to operate with
Internal Transport Barriers (ITBs) in order to reach adequate fusion gain at typical
currents of 9 MA. The large pressure gradients at the location of the internal barrier
are conducive to the development of ideal MHD instabilities that may limit the plasma
performance and lead to plasma disruptions. Fully non-inductive scenarios with ve
combinations of heating and current drive sources are presented in this work, with
plasma currents in the range of 7 to 10 MA. For each con guration the linear, ideal
MHD stability is analyzed for variations of the Greenwald fraction and of the pressure
peaking factor around the operating point, aiming at de ning an operational space
for stable, steady state operations at optimized performance. It is shown that lower
hybrid heating is desirable to maintain the safety factor pro le above 1.5 and that
these plasmas have better performance and more favorable MHD stability properties.
Operating with moderate ITBs at 2/3 of the minor radius leads to safety factor
pro les with minimum above 2, which signi cantly improves stability and extends
the operational space at normalized pressure above the ideal no-wall limit, although
weak, residual large-n ballooning instabilities remain.
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Submitted to: Nuclear Fusion (September 2011)
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Download PPPL-4690 (pdf 1.15 MB 28 pp)
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