Safe termination of fusion reactor discharges after disruptions

How to safely terminate a disrupted plasma discharge in reactor-scale tokamaks remains an open issue which is becoming increasingly urgent to resolve as the first reactor-scale tokamaks are set to begin operation within the next few years.

The greatest threat comes from relativistic so-called runaway electrons (REs) which can form in emergency shutdowns and cause severe damage to the tokamak wall.

In this project we aim to design emergency shutdown scenarios for reactor-scale tokamaks which avoid damage from REs.To achieve the goal we will first implement new physics models for the RE distribution function and companion plasma (thermal electrons, ions and neutral particles) in state-of-the-art simulation tools.

The new models will be validated against existing data from European tokamak experiments and used to interpret experimental observations.

With the new models, we will also determine how the currently most promising RE mitigation scheme, referred to as "benign termination", can be adapted to and optimized for the ITER reactor-scale tokamak.

In addition to providing insight into possible RE mitigation scenarios in ITER, the tools and techniques developed in this project can be transferred to other devices and will have application to the study of damage to wall material caused by REs, as well as in the design of RE diagnostics.