Control of instabilities in future fusion reactors

Fusion is a very promising energy source because it is clean and fuel is abundant. Unfortunately, the current test reactors suffer from instabilities for which reactor relevant control schemes are still lacking. This project aims to fill this gap.

PhD Candidate: Hugo van den Brand
Supervisor: Marco de Baar
Promotor: Marco de Baar
Project Financing: FOM Institute DIFFER
Project Period: April 2012 – April 2016

In future plasma reactors a plasma (ionized) gas will be contained in a toroidal shape (donut) using external magnetic fields and an internal current. The fields combine into a magnetic equilibrium that (depending on the equilibrium details) contains several instabilities.

Sawteeth are the result of one of these instabilities. In this case the temperature in the core builds and suddenly crashes. Large crashes can trigger other instabilities like magnetic islands. Therefore it is important to measure and control the period of the sawteeth which is known to relate to the size of the sawtooth crash. Implementation and development of advanced real-time sawteeth detection algorithms  is part of the project.

The magnetic islands that are triggered by sawteeth give rise to even larger problems. The magnetic islands grow and this leads to a lower temperature in the core (unfavourable for fusion) and, in some cases, even a complete destabilization that leads to a violent termination of the plasma. Unfortunately, sawteeth are not the only source that triggers magnetic islands. Therefore, a control scheme needs to be devised that suppresses existing islands. We are developing a collocated measurement and actuation scheme using microwave radiation for detection and microwave heating for island suppression.