Behaviour of Al2O3-oxide insulated and non-insulated superconducting MgB2 coils cooled by water ice

Wind-and-react coils made using non-insulated and/or Al2O3 oxide-insulated internal magnesium diffusion-processed MgB2 wires were energized at low temperatures with the help of sub-cooled water ice. The results demonstrate thermally stable winding behaviour and current densities (>10(4) A cm(-2) for T < 30.5-33 K) of oxide-insulated and metal-insulated MgB2 coils. The expansion caused by the water-to-ice transformation does not degrade the windings or the Al2O3 insulation. The thermometers and Hall probe are also undamaged over the full temperature range of 27-297 K. Consequently, water ice provides a cheap and safe prospective cooling mode for various superconducting windings and future He-free systems.