If you look at that second simulation, about midway through you can see the problem I was talking about, and FiatLuxDave goes into in more detail. The repulsive

If you look at that second simulation, about midway through you can see the problem I was talking about, and FiatLuxDave goes into in more detail. The repulsive force is keeping the density of the plasma very low, and you end up with a cloud of weakly interacting, orbiting ions that never fuse. The problem really is that the repulsive force increases enormously at very close ranges, so it may seem like the ions are colliding, but they’re not going to regularly have the energy required to overcome Coulomb repulsion, which remember increases with the inverse of the square of the distance. To overcome that you’d need to increase the strength of the magnetic containment, and shrink your container, but that will raise the density and change the behavior of your plasma while heating the walls of the chamber.