TY - JOUR

T1 - Modeling of diamagnetic stabilization of ideal magnetohydrodynamic instabilities associated with the transport barrier

AU - Huysmans, G.T.A.

AU - Sharapov, S.E.

AU - Mikhailovskii, A.B.

AU - Kerner, W.

PY - 2001/10/1

Y1 - 2001/10/1

N2 - A new code, MISHKA-D (Drift MHD), has been developed as an extension of
the ideal magnetohydrodynamics (MHD) code MISHKA-1 in order to
investigate the finite gyroradius stabilizing effect of ion diamagnetic
drift frequency, ω*i, on linear ideal MHD eigenmodes in
tokamaks in general toroidal geometry. The MISHKA-D code gives a
self-consistent computation of both stable and unstable eigenmodes with
eigenvalues |γ|≅ω*i in plasmas with strong
radial variation in the ion diamagnetic frequency. Test results of the
MISHKA-D code show good agreement with the analytically obtained
ω*i spectrum and stability limits of the internal kink
mode, n/m=1/1, used as a benchmark case. Finite-n ballooning and low-n
kink (peeling) modes in the edge transport barrier just inside the
separatrix are studied for high confinement mode (H-mode) plasmas with
the ω*i effect included. The ion diamagnetic
stabilization of the ballooning modes is found to be most effective for
narrow edge pedestals. For low enough plasma density the
ω*i stabilization can lead to a second zone of
ballooning stability, in which all the ballooning modes are stable for
any value of the pressure gradient. For internal transport barriers
typical of the Joint European Torus [JET, P. H. Rebut et al.,
Proceedings of the 10th International Conference, Plasma Physics and
Controlled Nuclear Fusion, London (International Atomic Energy Agency,
Vienna, 1985), Vol. I, p. 11] optimized shear discharges, the
stabilizing influence of ion diamagnetic frequency on the n=1 global
pressure driven disruptive mode is studied. A strong radial variation of
ω*i is found to significantly decrease the stabilizing
ω*i effect on the n=1 mode, in comparison with the case
of constant ω*i estimated at the foot of the internal
transport barrier.

AB - A new code, MISHKA-D (Drift MHD), has been developed as an extension of
the ideal magnetohydrodynamics (MHD) code MISHKA-1 in order to
investigate the finite gyroradius stabilizing effect of ion diamagnetic
drift frequency, ω*i, on linear ideal MHD eigenmodes in
tokamaks in general toroidal geometry. The MISHKA-D code gives a
self-consistent computation of both stable and unstable eigenmodes with
eigenvalues |γ|≅ω*i in plasmas with strong
radial variation in the ion diamagnetic frequency. Test results of the
MISHKA-D code show good agreement with the analytically obtained
ω*i spectrum and stability limits of the internal kink
mode, n/m=1/1, used as a benchmark case. Finite-n ballooning and low-n
kink (peeling) modes in the edge transport barrier just inside the
separatrix are studied for high confinement mode (H-mode) plasmas with
the ω*i effect included. The ion diamagnetic
stabilization of the ballooning modes is found to be most effective for
narrow edge pedestals. For low enough plasma density the
ω*i stabilization can lead to a second zone of
ballooning stability, in which all the ballooning modes are stable for
any value of the pressure gradient. For internal transport barriers
typical of the Joint European Torus [JET, P. H. Rebut et al.,
Proceedings of the 10th International Conference, Plasma Physics and
Controlled Nuclear Fusion, London (International Atomic Energy Agency,
Vienna, 1985), Vol. I, p. 11] optimized shear discharges, the
stabilizing influence of ion diamagnetic frequency on the n=1 global
pressure driven disruptive mode is studied. A strong radial variation of
ω*i is found to significantly decrease the stabilizing
ω*i effect on the n=1 mode, in comparison with the case
of constant ω*i estimated at the foot of the internal
transport barrier.

KW - Macroinstabilities

KW - Tokamaks spherical tokamaks

KW - Transport properties

U2 - 10.1063/1.1398573

DO - 10.1063/1.1398573

M3 - Article

SN - 1070-664X

VL - 8

SP - 4292

EP - 4305

JO - Physics of Plasmas

JF - Physics of Plasmas

IS - 10

ER -