抄録
Acoustic emission (AE) signals induced from the Central Solenoid Model Coil (CSMC) and the Central Solenoid Insert Coil (CSIC) of the International Thermonuclear Experimental Reactor (ITER) are described. Two kinds of AE data acquisition methods for the AE signals are adopted during series of energizing, i.e., one is the whole waveform recording, and the other is the AE envelope recording. It can be estimated that the AE signals are mainly induced by motion of a superconductor because the AE signals synchronize with the voltage spikes, especially in the virgin current region. The multi channel measurement provided us with information about the spatial distribution of disturbances by the AE sensors at each installed point in CSMC. The observation of AE with high-time resolution shows that the disturbances in CSMC decrease with the iteration number of excitation, judging from instantaneous AE levels, AE energies, and AE event count. Meanwhile, under the background field of 13T by CSMC, charging and discharging tests of the CSIC at the rate of 5kA/s from 0kA to 40kA were repeated 10, 003 times. We monitored the disturbances in CSIC and in CSMC during this cyclic test by using envelope signals of an AE sensor installed near the bottom of the innermost layer of CSMC. The detected AE signals were large, in the range of 1, 000 to 2, 000 times and 3, 000 to 4, 000 times. And after that, the AE signals were very small, until 10, 003 times. From 3, 000 through 4, 000 times, we monitored strange AE behaviors that can be attributed to the loosening of bolts.
