ABOUT SOME POSSIBILITIES OF INCREASING THE SENSITIVITY OF AN ANGLE PROBE USING A MATCHING LAYER BETWEEN A PIEZOPLATE AND A PRISM

Abstract

Based on computer modeling, the possibility of increasing the sensitivity of an angle probe when using a quarter-wave matching layer between a prism and a piezoplate with an optimal characteristic impedance of epoxy resin and phenoplast with tungsten filler and textolite is shown and quantitative estimates of such an increase are given in comparison with the case of the absence of a matching layer. The evaluation of the possibilities of using a quarter-wave metal matching layer made of magnesium and aluminum (for the nominal frequency of the 2.5 MHz probe) to increase the sensitivity was carried out. In the case of such an aluminum layer, the signal spectrum has two local maxima due to the relatively large layer impedance compared to the optimal value, which leads to distortion of the pulse shape and affects its duration. The presence of two spectrum maxima is due to the fact that the piezoplate and the matching layer are two coupled oscillatory systems with a coupling coefficient exceeding the value of the inverse acoustic Q-factor of the matching layer, decreasing with increasing its characteristic impedance.