Monitoring of superconducting magnets using acoustic resonance

A method to monitor a superconducting magnet is presented that utilizes a change in acoustic resonance frequency induced by events such as a local temperature rise or crack in epoxy. Some experiments are carried out on small epoxy impregnated magnets. Experiments to verify the method were carried out and applied sinusoidal acoustic signals were found to change with small changes in heat inputs to the magnet. The method was able to detect a local temperature rise of 2-3 K in the magnet before quenching occurred. Experiments with a wide-frequency pseudo-random input found no change in the ratio of the received-to-diver spectra when the internal state of the magnet was unchanged. However, for the local temperature rise of 2-3 K in the magnet, a significant change was observed.