Application of the Acoustic Emission Technique for Online Monitoring of Quench in Racetrack Superconducting Coil in a Cryogenic Environment

摘要

In this study, the training and degradation behavior of racetrack shaped superconducting magnets have been examined by aiming the high performance superconducting generator. The acoustic emission technique has been applied to detect quenching, which is one of the most serious problems in assuring the integrity of superconducting coil at a cryogenic temperature. The results have shown experimentally that the acoustic emission technique is very useful for detecting the quench of superconducting magnets as a nondestructive testing method and can be used to prevent premature quench. The correlation between training and degradation behavior and the fabrication condition of the magnets was studied by referring to the acoustic emission information. The characteristics of acoustic emission parameters have been analyzed by correlating them with the number of quenches, winding tension and current ramp rate by transport current of superconducting coil. The identification of quench source location was also performed using acoustic emission parameters, such as acoustic emission energy and acoustic emission events, including the quench current. In this study, it was confirmed that acoustic emission signals were mainly caused by the conductor motion, which was caused by premature quenching. It was also found that optimized winding tension at the superconducting coil was needed to prevent the quench.