Magnetically-confined plasmas are currently the most promising technological solution to achieve the target of producing electricity from nuclear fusion reactions. Several experimental reactors, mostly featuring the tokamak configuration, are being operated and designed around the world to address and solve the remaining open issues. The magnetic confinement relies on huge magnetic fields, produced by means of electromagnets, usually wound using superconducting cables. The latter show their superconducting properties only at low (high temperature superconductors) or very low (low temperature superconductors) temperature, so that they must be cooled down to the liquid nitrogen or liquid He temperature, respectively. Such a cryogenic power is provided by a refrigerator, whose technological complexity and cost are a significant fraction of those of the entire machine.