Thermomechanically driven helium II flow, an option for fusion magnets with internally cooled conductors

The authors investigate the option of magnet cooling with forced flow of helium II which is driven by fountain effect pumps. The problem of the small efficiency of fountain pumps is overcome by its appropriate arrangement in the circuit so that the heat which is picked-up by the superconducting device can be used to excite the pump. The cooling characteristcis of such systems are studied numerically for different pressures of the He II between 0.1 and 7 bar. For given peak temperatures in a winding this forced flow system allows much longer hydraulic channels than it would be for cooling by pure Gorter Mellink conduction. Thus this method offers the possibility to combine in magnet design the advantages of helium II and of internal forced flow