Permanent magnets for stellarators?

"Stellarators with Permanent Magnets" / Title article in Physical Review Letters 124/9

The cover of the current issue of the journal Physical Review Letters is decorated with a stellarator graphic. In the accompanying article, IPP scientist Per Helander and co-authors investigate whether permanent magnets can be used in stellarator-type fusion devices.

In their article "Stellarators with Permanent Magnets" the authors show that the magnetic field coils of a stellarator can be simplified considerably with the help of permanent magnets – at least in principle. Although permanent magnets are not suitable for generating the strong main magnetic field of a stellarator, they could be used to shape the plasma and to twist the field lines. The shape of the complex stellarator magnet coils – electromagnets made of superconducting cables – would be correspondingly simpler. As an example, the authors developed a stellarator configuration with only eight identical circular stellarator coils plus permanent magnets.

Another advantage is that permanent magnets do not require a power supply or cooling. On the other hand, they do not deliver high field strengths and can demagnetize under certain circumstances. The authors therefore emphasize that the focus of their investigation is on the mathematical aspects of the problem. Technical issues will be discussed subsequently.

Original publication
Helander, Per; Drevlak, Michael; Zarnstorff, Michael; Cowley, Steven:
Stellarators with Permanent Magnets
In: Physical Review Letters 124, Number 9, 095001 (2020),
DOI: 10.1103/PhysRevLett.124.095001