POSITION ESTIMATION OF LOCAL TEMPERATURE RISE IN EPOXY-RESIN STRUCTURE USING ACOUSTIC TRANSFER-FUNCTION

We have been developing a new method to detect a quench of a superconducting magnet using ultrasonic technique. This method detects a change of acoustic transfer function caused by a local temperature rise inside the magnet. So far, it has been confirmed that the generation of local temperature rise inside the magnet can be detected by this method. However, it has not been successful to locate the position of the local temperature rise in the magnet. Therefore, this time, we have 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. As mentioned above, the ultrasonic wave which transfers through the structure is modified characteristically by a disturbance generated inside the structure. Firstly, we have investigated some theoretical aspects of the mechanism explaining the change of the acoustic transfer function induced by the local temperature rise using one dimensional model. And, we have carried out some experiments on this matter. The theoretical result agrees well with the experimental one. Secondly, we have studied theoretically about the possibility of the position estimation of the local temperature rise by detecting the reflected acoustic signal from the local heated point. The simulation results of the transferring behavior of the ultrasonic signal perturbed by the local temperature rise inside the epoxy structure are shown.