Excitation experiments of module coil (TOKI-MC) as an R&D program for Large Helical Device

Excitation experiments for one of the R&D coils called TOKI-MC have been carried out to simulate the condition of excitation of helical coils for the Large Helical Device (LHD). TOKI-MC is a pool-cooled twisted solenoid coil with aluminum stabilized superconductors that were obliquely wound around an elliptical bobbin. In all nominal current excitations, quenches were initiated around 17 kA while the design current was 20 kA. There was no training effect. Signals of acoustic emission (AE) sensors indicated that the quenches were triggered by mechanical perturbations. It was found that the conductor of TOKI-MC moved freely without restriction due to the electromagnetic force, and that the winding moved reversibly. >