In nuclear fusion, the goal is to create and sustain (usually with magnetic fields) a high-temperature and high-pressure environment enough to output more energy than put in.
Tokamaks (donut shape) have been the topology of choice for many years. However, it is very difficult to keep the plasma confined within the walls because of its high surface area (especially in the inner rings).
Why hasn't anyone used spherical magnetic confinement instead (to mimic a star's topology due to gravity)? – Apart from General Fusion
E.g. injecting Hydrogen into a magnetically confined spherical space and letting out the fused energy once a critical stage has been reached?
Best Answer
Not an expert, but I believe the answer lies in the hairy ball theorem.
You see, for a magnetic field to turn charged particles back from a surface, the field must be parallel to the surface, which means that to have a fully confining geometry you must have a smooth, everywhere non-zero, and continuous vector field mapped onto a surface.
But the theorem say that you can't do that on a sphere (or topologically equivalent shape).