Acoustic emission during DC operations of the ITER Central Solenoid model coil

Acoustic emission (AE) signals from the Central Solenoid (CS) model coil developed in ITER program were studied during direct current (DC) operation. Estimation of the AE energy from the coil indicates close correlation between the AE energy and AC losses in the cable-in-conduit (CIC) conductor. This correlation comes from motions of the cables and dc-bonding of strands in the CIC conductors during repeated charging of the coil. The AE measurements clearly indicated the existence of mechanical disturbances even in the cases where the voltage spikes observed in the balance voltages were comparable to the noise level. In the case of the CS model coil, the locations of the mechanical disturbances could be determined using AE signals in combination with information from voltage spikes correlated with the AE signals.