High temperature superconductors provide more stable resistance-free conduction than traditional superconductors. If both are cooled to liquid helium temperatur

High temperature superconductors provide more stable resistance-free conduction than traditional superconductors. If both are cooled to liquid helium temperatures, that increased stability translates to being able to sustain a higher magnetic field. Higher magnetic fields provide tighter plasma confinement and higher density, which allows for much smaller fusion reactors.