Observation of the penetration of massive gas jet by fast frame camera on J-TEXT

A fast frame camera diagnostics has been developed to study the penetration of impurities gas jet on J-TEXT. The fast frame camera has 22 k frame rate with 640×480 pixel resolutions. The penetration processes of gas jet have been studied by the fast frame camera with optical filters. It is found that the gas jet propagated from the bottom to the high field side along the magnetic surface before the disruption. The cold front induced by the gas jet propagated into the plasma interior in the order of 200 m/s. The cold front was stopped at the location near the q=2 surface.