Application Of ECE Imaging And Study Of Sawtooth Reconnection Activities On EAST

This thesis consists of two parts.The first part presents the optical design of the Electron Cyclotron Emission Imaging (ECEI) system and the installation of the new ECEI system on the EAST tokamak.In the new optical design, a hyperboloid lens is used to restrict greatly the sphere abberation and channel interferences, the optimized lenses with two switchable modes of3P/4P are adapted. The setting up of the new novel ECEI system on the EAST machine has been worked successfully, and showed good performances with high resolution as well as good stability and flexibility. The electron temperature profiles and its fluctuation over an area of20cm (vertical) by6cm (horizontal) could been analyzed.The second part deals with the study of MHD activities by systematic and detailed analyzing of the ECEI data in EAST.Firstly, a new method based on ECE Imaging is developed which can give the information of the position of magnetic axis and the structure of internal magnetic surface for EAST tokamak.Secondly, the sawtooth evolution activities have been investigated on EAST tokamak and summarization as following:(1). When the plasma beta is high but qa is lowered which means the q-1radius is larger and q(r) profile is more smooth for sawtooth DI, the sawtooth precursor would be characterized by m/n=1/1and its higher harmonics; while if beta is low, the sawtooth DII characterized by compound sawtooth would be observed.(2). When the plasma beta is lower and qa is higher, the sawtooth A is characterized by ballooning mode.(3). When the plasma beta and qa is medium, the sawtooth evolution is characterized by Porcelli incomplete reconnection process, and sawtooth crash process are described by H. K. Park on TEXTOR.Moreover, we observed the sawtooth E characterized by mid-cursor oscillation with ICRF injection in divertor plasma; sawtooth F and G are characterized by the post-cursor oscillation and non-precursor oscillation were distinguished for the first time on EAST too.Finally, the toroidal coupling of tearing mode m/n=2/1with q～1surface was studied by ECEI on EAST. We have confirmed the spatial distribution of the coupling mode adjoin to q-1for the first time, and also found that the coupling strength bursts before the sawtooth precursor and disappears when the sawtooth oscillation begins. The time scale is about2-4ms.