Measurements of ultrasonic velocities using a digital averaging technique.

A new pulse-echo technique using real-time digital averaging is described for measuring the phase velocity in solids up to 50 MHz. The technique can measure the transit time between any two echoes to an absolute accuracy of 0.1 nsec and measure small changes in transit time to a sensitivity of 20 psec. Experimental examples are given based upon ultrasonic velocity measurements in a single crystal superconductor.