Detector for Measurement of Ultrasonic Strain Amplitudes in Solids

Abstract
A capacitive detector has been developed for strain amplitude measurements of longitudinal ultrasonic waves in the frequency range from 5 to 100 MHz. The sensitivity of the device is such that displacement amplitudes of the order of 10−10 cm can be detected. As a check of the technique, quantitative measurements of the harmonic distortion of ultrasonic waves in a single crystal of germanium were made. From the results, some combinations of third order elastic constants are calculated and are compared with values obtained with the same sample by another method.