Development A MGI Valve On J-TEXT Tokamak And Experiment Investigation Of The Runaway Current

Plasma disruption seems can't be avoided during the tokamak operations. Plasma disruption would damage the tokamak by the heat loads on the plasma facing components(PFC), the large electromagnetic force on the device and the runaway electrons will also impact and damage the PFC. Usually, pellet injection, massive gas injection(MGI) and liquid jets are used to mitigate the damages cause by the plasma disruptions. MGI is one of the prospective disruption mitigation method for it can mitigate the heat load reduce the electromagnetic force and partially suppress the runaway electronics. J-TEXT tokamak has lower plasma energy cause of its 1 ke V elections temperature, so it should be more advantage than the large tokamak devices to perform disruption experiments. Disruption experiments which performed on J-TEXT should provide available references for the ITER tokamak.Study on the different tokamak devices shown that even the MGI could not suppress the generation of the runaway electronics which would form runaway current in adaptive situations. MGI and resonant magnetic perturbations(RMPs) are proposed to mitigate the runaway current. In order to control and mitigate the runaway current, we should research the generation and the development of the runaway current. The runaway current on J-TEXT has been observed directly for the first time by using the soft X-ray detector array.In order to perform disruption mitigation experiments on J-TEXT a MGI valve have been designed. The MGI valve is based on the electromagnetic repulsion mechanism, so it can open fast and have a large gas flow. According to the mathematical computation and the Ansoft Maxwell simulation the MGI valve is designed as a 3 chambers structure which make it is easy to be assembled and is economic. The MGI valve has been tested by the 60 L vacuum chamber and a fast frame camera. It shows that the MGI valve is safety for the J-TEXT, the reaction time and the gas flow are suitable for the J-TEXT also.The MGI valve has been used on J-TEXT tokamak for the plasma disruption mitigation experiments. MGI valve performed very well on the safety, reaction time and gas flow during the experiment.