Can’t matrix bindings to superconductor be evaluated by its ultrasonic spectrum?

Abstract In the practical use of superconducting magnet, regardless of low or high temperature’ superconductor, combination of the superconductor and high conductive matrix of normal metal is now indispensable. This binding property is one of the key points whether superconducting characteristics are fully attained or failed prematurely in the practical magnet. But this binding evaluations is not so easy, because even in the mechanical well-jointed conductor in the room temperature, it often appears poor in electric and magnetic property in cryogenic temperature by the contraction of the conductor. And sometimes, these often happen that critical current change time to time of an every trial of current loading. This must be understood that the binding condition between the metals changes by time to time of heating and re-cooling at/after every quench. So it must become very important to evaluate these bindings’ properties at cryogenic temperature and with real current charging. Here we report new technique for evaluating these bindings by observing ultrasonic spectra of acoustic emissions when a normal transition is propagated along the superconductor. We have discovered a simple but important fact that good contacting conductor has an emission of this ultra-sound with sharp resonating frequency peak or peaks at around highest spectrum in near 1.0 MHz area.