Magnetic coils (blue) and plasma shape (yellow) in helias configuration. (Credit: IPP)

Modular stellarator using special crooked coils to create a magnetic field. The plasma has the shape of a twisted ribbon with a variable bean-shaped cross-section. The shape of the coils is calculated by computer; each is unique. However, in order to avoid manufacturing, say, fifty original coils, the helias consist of several (about 3 to 5) repeating sections. This is a very promising stellarator concept with good confinement. The helias configuration is used in for example the Wendelstein 7-X stellarator.