Position estimation of local temperature rise in epoxy resin structure using acoustic transfer function

A method of detecting a quench of a superconducting magnet using an ultrasonic technique is being developed. This method detects a change of acoustic transfer function caused by a local temperature rise inside the magnet. It was confirmed that the generation of local temperature rise inside the magnet can be detected by this method. However, it was not successful at locating the position of the local temperature rise. The authors tried to detect the location of the local temperature rise in a bulk structure made of epoxy resin as a model of a superconducting magnet impregnated by epoxy. The ultrasonic wave which passes through the structure is modified characteristically by a disturbance generated inside the structure. The authors investigated some theoretical aspects of the mechanism explaining the change of the acoustic transfer function induced by the local temperature rise using a one-dimensional model. They also carried out some experiments on this matter. The theoretical result agrees well with the experimental one