Linear gyrokinetic simulations of microinstabilities within the pedestal region of H-mode NSTX discharges in a highly shaped geometry

Coury, M.; Guttenfelder, W.; Mikkelsen, D.; Canik, J.; Canal, G.; Diallo, A.; Kaye, S.; Kramer, G.; Maingi, R.
Issue date: June 2016
Cite as:
Coury, M., Guttenfelder, W., Mikkelsen, D., Canik, J., Canal, G., Diallo, A., Kaye, S., Kramer, G., & Maingi, R. (2016). Linear gyrokinetic simulations of microinstabilities within the pedestal region of H-mode NSTX discharges in a highly shaped geometry [Data set]. Princeton Plasma Physics Laboratory, Princeton University.
@electronic{coury_m_2016,
  author      = {Coury, M. and
                Guttenfelder, W. and
                Mikkelsen, D. and
                Canik, J. and
                Canal, G. and
                Diallo, A. and
                Kaye, S. and
                Kramer, G. and
                Maingi, R.},
  title       = {{Linear gyrokinetic simulations of microi
                nstabilities within the pedestal region
                of H-mode NSTX discharges in a highly sh
                aped geometry}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2016
}
Abstract:

Linear (local) gyrokinetic predictions of edge microinstabilities in highly shaped, lithiated and non-lihiated NSTX discharges are reported using the gyrokinetic code GS2. Microtearing modes dominate the non-lithiated pedestal top. The stabilization of these modes at the lithiated pedestal top enables the electron temperature pedestal to extend further inwards, as observed experimentally. Kinetic ballooning modes are found to be unstable mainly at the mid-pedestal of both types of discharges, with unstable trapped electron modes nearer the separatrix region. At electron wavelengths, ETG modes are found to be unstable from mid-pedestal outwards for eta(e,exp)~2.2, with higher growth rates for the lithiated discharge. Near the separatrix, the critical temperature gradient for driving ETG modes is reduced in the presence of lithium, reflecting the reduction of the lithiated density gradients observed experimentally. A preliminary linear study in the edge of non-lithiated discharges shows that the equilibrium shaping alters the electrostatic modes stability, found more unstable at high plasma shaping.

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