Speaker
Yang Zhang
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1064.pdf
Tearing mode control with electron cyclotron resonant heating and
current drive on EAST tokamak
Y. Zhang1, Q. Yu2, X. J. Wang1, H. D. Xu1, H. H. Wang1, T. H. Shi1, S. Gu1, Y. Liu1, L. Q.
Hu1, Y. W. Sun1, F. K. Liu1 , X. Z. Gong1, X. D. Zhang1 and EAST team
1
Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
2
Max-Planck Institute for plasma physics, EURATOM Association, D-85748 Garching,
Germany
The experiments of m/n = 2/1 classical tearing mode suppressed by the ECRH/ECCD have
been performed on EAST tokamak. The continuous EC beam with different power is
injected perpendicularly into the L-mode plasma and deposited at the radial position of the
magnetic island, i.e. ρ = 0.5. It is found that the magnetic island size is reduced gradually as
the ECRH power increases from 100 kW to 250 kW, and then it goes to a saturated value
(60% of initial size) even if its power increases further, indicating that the classical tearing
mode cannot be suppressed completely. This can be explained by the stabilization
mechanism which comes only from the temperatures inside the island separatrix. The
smaller the island size is, the less the heating area is. The minimum power for the effective
stabilization of the tearing mode is 100 kW, which is only about 6% of background plasma.
The deposition position of the EC beam is moved from plasma core to edge shot by shot
with fixed power of 320 kW. The results shows that the stabilization effect of
ECRH/ECCD can be observed in a wide region of ρ = 0.3 - 0.6, however the destabilization
effect is enhanced at the plasma core. This can be explained by the fact that the current
density profile tailored by ECRH/ECCD changes the magnetic shear and therefore
decreases the classical stability index Δ'. It is supposed that the heating rather than the
current driver plays an more important role in the des-/stabilization of the 2/1 mode in these
low beta discharge. Moreover, the RMP is further applied to control the island rotating
slowly, and the stabilization effect of ECRH/ECCD on the island's O and X points with
either an inward or outward misalignment allows to be investigated deliberately. The
preliminary analysis presents that a good stabilization effect is achieved by ECRH with an
inward misalignment of 3 cm relative to the radial location of the magnetic island rather
than by ECCD with the almost alignment.
