Electron Cyclotron Current Drive on Magnetic Axis

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1.We equiped soft X-ray cameras, and data acquisition and analysis system for observation of MHD instabilities in the WT-3 tokamak during electron cyclotron heating (ECH) and current drive.2.When we inject ECH power (56GHz 200 kw) and deposit the power on the magnetic axis, an MHD instability with the poloidal mode number m=2 and toroidal mode number n=1 is appeared. While, sawtooth oscillation associate with an m=2/n=1 precursor is appeared in the case of offmagnetic axis ECH.3.We observe a sawtooth crash associated with an m=2/n=1 precursor in a combined Ohmically heated and lower hybrid current drive plasma. A crash associated with an m=3/n=2 follows this crash several seconds later. We investigate these crashes by using seven soft X-ray cameras and computer tomography technic and compared the results with those of usual sawtooth crashes associated with m=1/n=1 precursors.4.We have equiped a new ECH system using an 88 Ghz gyrotron and its quasi-optical transmission and injection system. We will refine the investigation with this ECH system.