Nonlinear MHD simulations of QH-mode DIII-D plasmas and implications for ITER high Q scenarios

F Liu, G T A Huijsmans, A Loarte, A M Garofalo, W M Solomon, M Hoelzl, B Nkonga, S Pamela, M Becoulet, F Orain, D Van Vugt
2017 Plasma Physics and Controlled Fusion  
Liu, Feng; Huijsmans, G.T.A.; Loarte, A.; Garofalo, A.M.; Solomon, W.M.; Hoelzl, M.; Nkonga, B.; Pamela, S.; Becoulet, M.; Orain, F.; van Vugt, D.C. Abstract In nonlinear MHD simulations of DIII-D QH-mode plasmas it has been found that low n kink/ peeling modes (KPMs) are unstable and grow to a saturated kink-peeling mode. The features of the dominant saturated KPMs, which are localised toroidally by nonlinear coupling of harmonics, such as mode frequencies, density fluctuations and their
more » ... on pedestal particle and energy transport, are in good agreement with the observations of the edge harmonic oscillation typically present in DIII-D QH-mode experiments. The nonlinear evolution of MHD modes including both kink-peeling modes and ballooning modes, is investigated through MHD simulations by varying the pedestal current and pressure relative to the initial conditions of DIII-D QH-mode plasma. The edge current and pressure at the pedestal are key parameters for the plasma either saturating to a QH-mode regime or a ballooning mode dominant regime. The influence of E×B flow and its shear on the QH-mode plasma has been investigated. E×B flow shear has a strong stabilisation effect on the medium to high-n modes but is destabilising for the n=2 mode. The QH-mode extrapolation results of an ITER Q=10 plasma show that the pedestal currents are large enough to destabilise n=1-5 KPMs, leading to a stationary saturated kink-peeling mode.
doi:10.1088/1361-6587/aa934f fatcat:kzymmelxufajjeyrj4k57lwxiq