This is not my field (just an enthusiast) but consider that a typical fusion plasma has a density of 10^20 particles per cubic meter. Even if your plasma is 1 c

This is not my field (just an enthusiast) but consider that a typical fusion plasma has a density of 10^20 particles per cubic meter. Even if your plasma is 1 cubic centimeter, that's still 10^14 particles! Thus a full-on EM simulation, where every charged particle interacts with every charged particle, is not practical. A full-scale simulation is still unrealistic even if you typically cheat by breaking the problem up into cells and ignoring the Coulomb interaction beyond cell boundaries. Fusion machine design is a combination of hard-won experimental knowledge and theoretical guesswork. I'm skeptical of the current wave of fusion startups simply because they don't have the weight of the decades of experimental work that have gone into tokamak research. But hey, they might make a breakthough, who knows.