A high-current relativistic electron beam can form in tokamak-type fusion devices in start-up and uncontrolled shut-down scenarios. This beam can be collisionally detached from the bulk electron population of the tokamak plasma, and its description in a self-consistent way is still a challenge. As the tokamak line of devices approaches the reactor scale, this issue of runaway electrons is becoming a serious problem, maybe even a show-stopper. 

In recent years, a set of highly sophisticated modeling tools have been developed to tackle the problem, e.g., the DREAM self-consistent disruption simulator. The DREAM code has been successfully used on several present-day tokamaks, and it has been used for predictive calculations of future devices. The code can be, therefore, considered to be validated for current devices, but there are some significant differences between current and reactor-scale tokamaks that might significantly affect the dynamics of the runaway electron beam. The two most evident factors are the radioactive activation of the wall and the long wall-time due to the massive blanket and wall structures.

The doctoral student will be tasked with exploring the effects of changing parameters as we approach the reactor-scale. This will include extensive numerical studies using code packages like DREAM, as well as participation in the experiment interpretation at JT-60SA and other relevant tokamaks.