Stabilization Of The Double Tearing Mode By External Current Drive

Double tearing mode(DTM) instability easily occur with a non-monotonic safety factor q in the tokomaks. In the nonlinear development stage of DTM instability, the scale of magnetic island will grow exponentially and ultimately result in plasma disruption, which seriously effect the confinement of tokomaks. It is significant to study the control of DTM instability for development of magnetically confined plasma.Considering the external drive current in Hall MHD equations, the effects of external current drive on the instability of DTM are numerically investigated. Firstly, the effects of the external-driven current with the different position and direction on the development of DTM are studied,the results show that the count-direction external-driven current in the X-point has a powerful effect on DTM. The suppression effects of the continuous external-driven current will change, and the periodic driving current are adopt to suppress the DTM. Secondly, the effects of the external-driven current on the DTM in the nonlinear phase is studied. The results indicate that the external-driven current before the nonlinear phase of the DTM can suppress the DTM instability. Comparing with the count-direction external-driven current in the X-point and co-direction external-driven current in the O-point of the island, the effect of the former is better than the latter. Lastly, the effects of the period, width,adding time and strength of the external-driven current on the DTM. The results suggest that the right frequency, density and width of the periodic external current drive has a good effect on stabilizing the double tearingmode, and make the development of the DTM in the initial phase.