The Calibration Of High-speed CCD Imaging System On EAST And Its Preliminary Application In The Elm Dynamics Diagnosis

Tokamak is the main way to realize the magnetic confinement controlled nuclear fusion. There are various MHD instabilities in Tokamak plasmas. ELM is a typical MHD instability phenomenon under the H-mode operation. It is an important way to study the physical mechanism of ELM bursting by exploring the dynamics process of ELM filamentous structure.With the development of CCD technology, high speed CCD has become an important diagnosis for the fast and multidimensional instability process in Tokamak. In order to obtain the real physical process from the high-speed CCD image, the calibration of CCD imaging system is absolutely necessary. The calibration of the high speed CCD imaging system on the EAST was conducted. According to the characteristics of the EAST, the Tsai’s two step calibration method was chose and the passive plate was used as the calibration template. The Harris’ corner detection algorithm was used to identify the corners of the passive plate. The corresponding relationship was established by using the matrix of the spatial coordinates and the matrix of corner detection of the passive plate, and the CCD camera was calibrated. Based on the error analysis, the reliability of the calibration algorithm was analyzed and verified.By using the calibrated high speed CCD imaging system, the three-dimensional reconstruction of the ELM filamentory structure in H-mode was performed. The dynamic parameters, such as width, velocity and acceleration of the filaments motion were analyzed and obtained. It was found that the ELM filament width decreased with the increase of the auxiliary heating power through analyzing the characteristics of ELM filaments in different discharge conditions, and the velocity and acceleration characteristics of the ELM are also compared. The results present the base for the further study of the spatio-temporal evolution of ELM.