Observation of m = 0 structure streak picture in a reversed field pinch having large magnetic Reynolds number

The technique of streak pictures with an image converter camera (IMACON) has been applied to the STP-3(M) reversed field pinch (RFP) experiments. A pattern of stripes in the streak pictures has been observed. This pattern is typical that of plasma with large magnetic Reynolds number S (S ≥ 500). Each stripe has the m = 0, low n structure, where m and n are the poloidal and toroidal mode numbers, respectively, which correlates with m = 0 magnetic fluctuations. The origin of this m = 0 structure is ascribed to nonlinear interaction of the m = 1 modes which play essential roles in the RFP dynamo. It is thus demonstrated that the streak pictures are an efficient means of understanding the nonlinear mode coupling in RFP plasma. Further applications of the IMACON to the RFP experiments are also discussed. (author)