Pressure distribution measurements at the shock wave focus in water by schlieren photography (kidney/gall stone lithotripsy)

A shock wave in water was generated by an electric spark in the first focus of a truncated ellipsoidal reflector. From schlieren pictures of the reflector second focus region, taken at the moment the shock wave has reached it, radial pressure profiles of the focused shock wave were evaluated. The accuracy of the method used was tested by ray tracing through a semi-spherical layer inhomogeneity and by inverse reconstruction of the refractive index. The method was found to be useful for a qualitative indication of the pressure distribution at the second focus but laborious and inaccurate for a quantitative evaluation of the pressure.