How does 3-dimensional shaping produce rotational transform?
This is a somewhat subtle aspect of stellarators. However, there is an analogy to water flowing around a donut-shaped pipe which has been used. Both the magnetic field and the flowing water are incompressible vector fields with a particular direction at every point so they will share some of the same properties. If you then took the toroidal pipe and either twisted it, or placed appropriate dents and bulges around it, one can imagine that the flow of water will become re-directed so that it is no longer moving only around the donut (toroidal direction). In particular the water may tend to develop swirls or velocity components the short way around the donut. This is equivalent to the rotational transform in the magnetic field that stellarators produce by 3-dimensional shaping. • What are flux surfaces and why are they important? Magnetic flux surfaces are the surfaces formed by the magnetic field as it wraps many times around the torus. The confined plasma tends to form isobars or const
