Stellarator versus tokamak in the race for nuclear fusion
Since the late 1950s, attempts have been made to obtain energy through nuclear fusion (the merging of atomic nuclei into heavier ones, unlike nuclear fission or splitting, on which current nuclear power plants are based) through magnetic confinement of plasma, mainly using two different configurations: tokamaks and stellarators.
Tokamak reactors (Russian acronym for toroidal chamber with magnetic coils) are the most widespread. ITER, the largest nuclear fusion experiment being built in France to demonstrate the scientific and technological viability of this technology, is based on the tokamak model.
The correct topology of the magnetic fields for confining plasma in the Wendelstein 7-X stellarator has been verified, but stellarator-type reactors nevertheless offer certain advantages over tokamaks in terms of stability and absolute external control. In stellarators, the magnetic field used for plasma confinement is generated entirely by external coils with complex geometries.
In tokamaks, part of this magnetic field is generated by an alternating current induced in the plasma. However, this net current in the plasma is the source of most of the instabilities that occur in a tokamak and complicate its operation.
In this context, the international Wendelstein 7-X project is based on an advanced stellarator model that maximises the macroscopic stability of the plasma. Its construction was completed at the Max Planck Institute for Plasma Physics (IPP, Germany) in Greifswald in 2015, although it was not fully operational until 2018. The Plasma Science and Fusion Technology group at the National Accelerator Centre (CNA, Seville) is participating in the project.
Systems similar to the W7-X stellarator already exist in Spain, specifically the TJ-II stellarator at the CIEMAT National Fusion Laboratory, which has a radius of 1.5 metres and confines the plasma with a magnetic field of up to 1.2 teslas, while the German design has a radius of 5.5 metres and confines the plasma with magnetic fields of up to 3 teslas.
With the help of the latest advances in nuclear fusion and increased computing power, scientists from CIEMAT and the Carlos III University of Madrid have also collaborated in the presentation of the complex design of the W-7X stellarator.
