Speaker
Nikolay Ivanov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1037.pdf
Reverse of Tokamak Plasma Rotation under Tearing-Mode Locking by
External Resonant Magnetic Perturbation
N.V. Ivanov, A.M. Kakurin
National Research Centre «Kurchatov Institute», Moscow, Russia
Rotation of tokamak plasma attracts considerable attention in the fusion research
because this rotation, particularly under shear of rotation velocity, affects plasma stability
and confinement. The plasma rotation velocity in the vicinity of a rational magnetic surface
can be influenced by the development of the tearing mode. According to experiments and
numerical modelling, the tearing-mode locking by externally applied static Resonant
Magnetic Perturbation (RMP) can be followed by a rotation reverse of the Resonant Plasma
Layer (RPL) occupied by magnetic island structure (see [1, 2]). This reverse extends due to
plasma viscosity to some area surrounding the RPL.
Results of calculations and analysis of the plasma rotation reverse subject to the
tearing mode locking are presented in this paper. The main attention is paid to conditions
necessary for the rotation reversals separately in toroidal and poloidal directions, as well as
for the concurrent changes of both rotation directions. The dynamics of the plasma toroidal
and poloidal rotation-profile variations are also presented. The TEAR code [3, 4] used for
the calculations is based on the visco-resistive MHD approximation that gives coupled
diffusion-type equations for the magnetic flux perturbation and for the plasma rotation
velocities in toroidal and poloidal directions. In the case of sufficiently large magnetic
islands [5] the mode locking occurs due to the effect of the RMP-produced electromagnetic
torque applied to the RPL. The toroidal and poloidal electromagnetic torque components
are balanced by corresponding components of the viscous torque depending on the RPL
rotation velocities with respect to plasma velocities outside RPL. At the mode locking, the
superposition of the RPL toroidal and poloidal velocity projections on the direction of the
mode phase velocity (the [r×B] direction) is inhibited till the full stop of the mode rotation.
Therefore, if the initial directions of these velocity projections coincide, one of the toroidal
or poloidal velocities can change its sign. These alternative possibilities depend on the
interrelation between plasma toroidal and poloidal viscosity coefficients. The concurrent
reversals of the RPL toroidal and poloidal rotation velocities at the mode locking can occur
under the account of the electron diamagnetic drift in the mode rotation [6, 7].
[1] Hender T.C., et al. Nucl. Fusion 32 (1992) 2091
[2] Ivanov N.V., Kakurin A.M. Nucl. Fusion 57 (2017) 016021
[3] Ivanov N.V., Kakurin A.M., Konovalov S.V. 24th IAEA FEC (2012) TH/P3-22,
PAS&T/TF 36, v. 2, p. 55 (2013), see http://vant.iterru.ru/vant_2013_2/6.pdf
[4] Ivanov N., Kakurin A.M. Physics of Plasmas 21 (2014) 102502
[5] Eliseev L.G., et al. Physics of Plasmas 22 (2015) 052504
[6] Hosea J.C., et al. Phys. Rev. Lett. 30 (1973) 839
[7] Fitzpatrick R. Nucl. Fusion 33 (1993) 1049
