Check out the papers from the MIT SPARC folks. Getting the magnets working is not the bottleneck at all. REBCO and similar commercially available products are p

Check out the papers from the MIT SPARC folks. Getting the magnets working is not the bottleneck at all. REBCO and similar commercially available products are physically robust. Seriously, two grad students set a new field record doing nothing more complicated than spooling the stuff into a spiral. In terms of engineering, the diverter, and a wall that can last years are far, far, more difficult than the magnets.