MIT's simple ARC reactor for nuclear fusion power plants
Advances in magnet technology have enabled researchers at MIT to propose a new design for a practical compact tokamak fusion reactor. MIT's new reactor is named as the ARC reactor.
Rare-earth barium copper oxide (REBCO) superconducting tapes are the enabling technology behind the ARC reactor. When it is cooled to liquid nitrogen temperature, the superconducting tape can carry as much current as the large copper conductor, enabling the construction of extremely high"field magnets, which consume minimal amounts of power.
https://www.youtube.com/watch?v=O3ECJSEeW_A&list=PLK2ccNIJVPpB_XqWWq_oaZGIDzmKiSkYc
http://www.techtimes.com/articles/76112/20150812/tiny-fusion.htm
Rare-earth barium copper oxide (REBCO) superconducting tapes are the enabling technology behind the ARC reactor. When it is cooled to liquid nitrogen temperature, the superconducting tape can carry as much current as the large copper conductor, enabling the construction of extremely high"field magnets, which consume minimal amounts of power.
https://www.youtube.com/watch?v=O3ECJSEeW_A&list=PLK2ccNIJVPpB_XqWWq_oaZGIDzmKiSkYc
http://www.techtimes.com/articles/76112/20150812/tiny-fusion.htm
There are other problems, huge ones, but until some progress is made on this overriding one, we are just stumbling helplessly in the dark.
I assume that many if not all Tokamaks have used superconducting magnets. You don't run currents of millions of amperes through copper. Not for long (more than milliseconds). Even if you had enough copper to carry it and enough refrigeration to keep the copper from melting, losses would be collossal.