Curved Quartz Crystals as Supersonic Generators Available to Purchase

The supersonic beam radiated from a one‐centimeter radius X‐cut quartz disk is examined experimentally as a function of the spherical curvature of the crystal, at a frequency of 1110 kilocycles. The crystals of large curvature produce a definite focusing action as has been reported from an earlier investigation. The experimental data show that it is possible to obtain a much greater excess pressure amplitude close to the generator from a curved crystal than is possible from a flat crystal having the same area and thickness using the same input power. The quartz plates of small curvature do not produce a marked focusing action but give a larger supersonic amplitude at large distances from the generator. The flat crystal gives the smallest angle of spread of the supersonic beam. The resonant frequency for any of the five crystals studied did not differ by more than 20 kilocycles (2 percent) from that to be expected from the thickness.