Observation of Edge Plasma Fluctuations with a Fast Camera in Heliotron J

fast video camera is verifi to be a powerful tool for observation of fiments/blobs near the last closed °ux surface (LCFS). In order to extract the fltuation component from the raw data of the fast camera, a pre-processing technique, sliding time window averaging subtraction (STWAS) has been developed to remove the background of slowly varying emission from the bulk plasma. By using this pre-processing technique, the fast camera data are analyzed. A method to identify the fiments in the pre-processed image is also discussed.