A schlieren probe method for the measurement of the refractive index profile of a shock wave in a fluid

The time variation of the deflection of a narrow probe laser beam which is traversed by the shock wave is compared with the theoretical deflection for a model refractive index profile obtained by computer ray tracing. The technique has been applied to the measurement of the pressure in a shock wave generated by the impact of a focused carbon dioxide laser pulse on a water surface. The spatial resolution of the technique is controlled by the diffraction limits of the probe laser beam. In experiments on a 1 mm radius shock wave, peak refractive index changes of 0.2%, corresponding to a pressure of 1.84*107 Pa, have been recorded. The derived acoustic energy in the shock is 13 mu J.