ECCD DTM POP201509

(Received 18 March 2015; accepted 24 August 2015; published online 16 September 2015)
The effects of electron cyclotron current drive (ECCD) on the double tearing mode (DTM) in slab geometry are investigated by using two-dimensional compressible magnetohydrodynamics equations. It is found that, mainly, the double tearing mode is suppressed by the emergence of the secondary island, due to the deposition of driven current on the X-point of magnetic island at one rational surface, which forms a new non-complete symmetric magnetic topology structure (defined as a non-complete symmetric structure, NSS). The effects of driven current with different parameters (magnitude, initial time of deposition, duration time, and location of deposition) on the evolution of DTM are analyzed elaborately. The optimal magnitude or optimal deposition duration of driven current is the one which makes the duration of NSS the longest, which depends on the mutual effect between ECCD and the background plasma. Moreover, driven current introduced at the early Sweet-Parker phase has the best suppression effect; and the optimal moment also exists, depending on the duration of the NSS. Finally, the effects varied by the driven current disposition location are studied. It is verified that the favorable location of driven current is the X-point which is completely different from the result of single tearing mode. VC 2015 AIP Publishing LLC. [/10.1063/1.4930535]
1Basic Science Section, North China Institute of Aerospace Engineering, Langfang 065000, China 2School of Computer and Remote Sensing Information Technology, North China Institute of Aerospace Engineering, Langfang 065000, China
PHYSICS OF PLASMAS 22, 092509 (2015)
Effects of electron cyclotron current drive on the evolution of double tearing mode
Guanglan Sun,1,a) Chunying Dong,1 and Longfangห้องสมุดไป่ตู้Duan2
a)E-mail: sunguanglan@
distances between the two rational surfaces Drs (small, intermediate, and large).9,10 The fast DTM reconnection phase was reproduced by Wang et al. in slab geometry, which indicates the universality of the two-dimensional (2D) DTM events.11 Recently, Wang et al. theoretically and numerically revealed that the self-induced Alfven resonances in the RMS configuration can decouple the DTMs and suppress them effectively as a new stabilization method.12,13,24
I. INTRODUCTION
Tearing mode (TM) is one of the most important magnetohydrodynamic (MHD) instabilities in the tokamak plasmas. Magnetic energy is quickly transferred into plasma thermal energy or kinetic energy, and then results in the magnetic energy dissipation during the magnetic reconnection process induced by the unstable TM.1 One of the main improvements for magnetic confinement in advanced tokamaks is the reversed magnetic shear (RMS) configuration. This RMS configuration is really a promising scenario, as the internal transport barriers (ITBs) might be triggered near the location of minimum safety factory qmin,2–4 where the turbulent transport is suppressed significantly, and thereby the high energy plasmas are achieved in the core region. However, such configuration can be highly unstable regarding to the development of MHD instabilities,5 due to the existence of two rational surfaces. In particular, the double tearing modes (DTMs) can become unstable and have already been observed in some tokamak discharges.6–8 Islands developing on each tearing layer can interact with each other, exchange their position, and lead to the total reconnection of magnetic field lines, along with the total loss of plasma stability. Many of theoretical and numerical investigations focused on the developments of DTMs have been studied.9–24 To understand the characteristics of MHD activities in JT60-U plasmas with strong RMS (qmin > 2), Ishii et al. systematically compared the radial eigenmode structures of DTMs with helicity h ¼ 3, in the cases of different
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Effects of electron cyclotron current drive on the evolution of double tearing mode
Guanglan Sun, Chunying Dong, and Longfang Duan Citation: Physics of Plasmas 22, 092509 (2015); doi: 10.1063/1.4930535 View online: /10.1063/1.4930535 View Table of Contents: /content/aip/journal/pop/22/9?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Curvature effect on tearing modes in presence of neoclassical friction Phys. Plasmas 20, 112504 (2013); 10.1063/1.4829038 Hybrid simulation of energetic particle effects on tearing modes in tokamak plasmas Phys. Plasmas 19, 072506 (2012); 10.1063/1.4736956 Double tearing mode induced by parallel electron viscosity in tokamak plasmas Phys. Plasmas 17, 112102 (2010); 10.1063/1.3503584 Dynamics of resistive double tearing modes with broad linear spectra Phys. Plasmas 14, 022107 (2007); 10.1063/1.2446420 Effect of sheared equilibrium plasma rotation on the classical tearing mode in a cylindrical geometry Phys. Plasmas 14, 012101 (2007); 10.1063/1.2424427