> I agree that the larger the area enclosed by the coil, the larger the
> storage capacity relative to the current and number of turns. I think
> the storage capacity of a superconductive coil is simply equal to the
> energy of the magnetic field created by the coil, which would be
> proportional to the product of the current, the area enclosed, and the
> number of turns; at least for a Helmholtz-style coil.
You also don't have to deal with monstrous forces.
While speaking of coils, doped buckytube ropes seem to be able to withstand monstrous current densities at a very low resistance, iirc dramatically below silver. A way to build a MRI RT coil?