Experimental study of construction mechanism of V(z) curvesobtained by line-focus-beam acoustic microscopy

摘要

The propagation characteristics, viz., phase velocity andnattenuation, of leaky surface acoustic waves (LSAWs), excited on thenwater/sample boundary are obtained through analyzing the V(z) curvesnmeasured by line-focus-beam acoustic microscopy. However, differentnvalues of these characteristics are obtained, depending upon differentnultrasonic devices and operating frequencies employed. The constructionnmechanism of V(z) curves was investigated experimentally by measuringnthe amplitude and phase for Teflon to provide an understanding of thendevice performance for velocity measurements. A V(z) curve measured fornTeflon, on which no leaky waves are excited when water is the couplingnmedium, can be used for the characteristic device response, dependingnonly upon the device parameters and the operating frequencies. From theninvestigation of the ultrasonic device and the frequency dependences ofnthe characteristic device responses, the phase gradient was found to bendirectly related to values of measured LSAW velocities. From thisnresult, apparent frequency dependences in LSAW velocity measurements arenexplained quantitatively for a specimen of gadolinium gallium garnet