A visible light high-speed imaging system and tomographic reconstruction of plasma emissivity on the J-TEXT tokamak

A visible light high-speed imaging system has been installed on the J-TEXT tokamak to measure the spatial distribution of visible emission in the vacuum chamber. The system views the plasma tangentially from an outer port at the height of the mid-plane of the vacuum vessel. An optical system is designed for the consideration that the camera must be installed away from the magnetic field. A spatial calibration based on Tsai's method is adopted to build the relationship between the tokamak 3-D space coordinate and the 2-D image coordinate. Tomographic reconstruction techniques are used to calculate the 2-D poloidal emission profiles from the camera image data assuming toroidal symmetry of the radiation. Sample results are presented to view the discharge process in typical plasma discharge and methane injection experiments with a CIII-filter added. And the 2-D poloidal CIII emission profiles reconstructed from imaging results in typical plasma discharge experiments are also obtained.