Thomas Dickerson @elfprince13@mumak.app

@kyrsjo @veronica there are some other variations playing with the curvature of the basic toroidal design within this overall space, but that's the basic gist of the MCF game*.

*if you really want to deep dive there are also Field-Reverse Configurations (FRCs), which have a few passionate devotees, but are even more stalled (public-) funding wise than stellarators.

@kyrsjo @veronica anyway, politics aside, the tokamak folks basically just need to make a "big enough" model so that the curvature isn't too crazy to get the confinement they want (ITER), or just build an insanely powerful magnet to do it at a reasonable scale (CFS).

@kyrsjo @veronica this had led to a bunch of political decisions wherein tokamaks get favored as the "easy" solution, and stellarators have a hard time getting funded despite being the "more correct" approach (PPPL literally has a stellarator in pieces in a garage because funding got cut before they were allowed to put them together)

@kyrsjo @veronica with a stellarator you physically bend the plasma into a shape that induces its own useful magnetic field, in such a way that you have a globally average good curvature minimizing the tendency to drift outward, but sadly the solutions to the differential equations letting you physically realize this really cool idea leads to shape require stupidly tight tolerances to manufacture and are thus much more expensive to build at any kind of scale.

@kyrsjo @veronica Moreover, the magnetic field is weaker on the outside of the torus due to relative increase in surface area with same number of coil windings, so as particles take random walks out through the field, you get one-sided error, and they begin to concentrate outward which is bad

@kyrsjo @veronica so this is related to one of the reasons I historically have favored stellarators - with a tokamak you're imposing an external magnetic field on the plasma (which really just wants to faff about and do its own thing).