Disruptions – a proposal for their mitigation by runaway suppression

The avoidance of disruptions is essential for the next generation tokamaks. The dangerous consequences of disruptions are excessive heat loads, high forces, creation of high-energy runaway electrons, and a bad conditioning for the start of the following discharge. In order to mitigate these effects, a fast valve has been developed on TEXTOR with a response time to full opening of 1 ms after a trigger pulse. The fast injection of helium by such a valve suppresses runaway electron production and even removes them if present. The reaction time of the valve is fast enough to apply it even after the start of a disruption. The fast gas injection has been applied to a nearly stationary runaway discharge and it was successfully shown that the energetic electrons are quickly expelled.