Relation between hard X-ray emission and runaway electrons in Damavand tokamak

In this experimental work, hard x-ray emission in Damavand tokamak along with the temporal evolution of plasma current and loop voltage have been studied for shots in which plasma current varies from 17 to 32kA. The time evolution of plasma current from beginning of the discharge to the disruption phase, loop voltage, and hard x-ray emission has been analyzed. The hard x-ray emission for the plasma current less than 20kA has been observed during the disruption phase, where the discharge duration is less than 10ms. For plasma current is more than 20kA, however, hard x-ray can be observed at the beginning to the disruption phase and it persists for 20ms. Two kinds of regimes can be realized for the runaway electron production in this tokamak. The first regime is similar to other tokamaks and takes place during the disruption phase. This regime is understood by Dreicer theory of runaway electron production. The second regime which is observed from the beginning to the end of discharge is related to the avalanche event.