AE technique is expected to be an useful monitoring and diagnosing technique for superconducting magnet. Already, it has been proven that AE technique is a powerful tool to identify and understand causes of magnet quenches. In the paper, the developement of AE technology as it is applied to superconducting magnet is reviewed. Future directions of research are also discussed.
Origins of AE are investigated. It is shown that wire motions and other mechanical disturbances are dominant AE sources and that flux motion, except flux jumping, produces no descernable AE signals. Papers concerning AE sources are reviewed and the results are compared.
The monitoring superconducting magnet by its acoustic emission has been found effective during the operation of the magnet. We have observed various AE from the magnet. Sources of AE generation are roughly classified and ordered according to their strength of AE, i.e., fracture of conductor destruction, conductor movement, fracture of support material, magnetization of conductor and S/N transition. Here, acoustic emission during the magnetization of the conductor and the magnet are mainly explained by showing the experimental results and theoretical discussions. The AE due to magnetization has been found to be related to the magnetic flux movement by Lorentz force.
Application of acoustic emission (AE) measurement to the superconducting magnet is reviewed. Four kinds of applications are available at the moment: (a) Simultaneous measurement of AE and coil voltage, which is used to identify the quench origin. (b) Measurement of AE count rate during coil charging, appropriate to recognize the general trend of mechanical disturbance occurence in the magnet. (c) Spectrum analysis of an AE signal generated by a vibrator which is suitable for long range diagnosis of the magnet system. (d) Location of electrical breakdown of instrumentation wires. Each of the techniques is briefly reviewed and compared in this paper.