Piezoelectric generation of variable focussed shock waves

For detailed investigation of the relations between biological shock wave effects and the relevant shock wave parameters (compression, dilatation, fundamental frequency, pulse power, etc.) a variable shock wave source was built. It consists of an arbitrary function generator, a linear power amplifier, a pulse-compressing electrical network, a plane piezoceramic transducer and a focusing lens (polystyrene). Shock waves with compression up to 32 MPa and dilatation up to 10.5 MPa in the focus (water) can be generated using experimental systems with fundamental frequencies of 450 kHz and 750 kHz, respectively. The ratio of compression to dilatation is variable within a range of 5 dB, and it is possible to generate inverted shock waves, starting with a dilatation phase. Variation limits are mostly by the generation of cavitational bubbles in the focal region that seriously damp a main part of the signal