QUANTITATIVE SCHLIEREN MEASUREMENTS OF A HIGH-ENERGY ELECTROMAGNETIC TRANSDUCER ACOUSTIC SHOCK FIELD

Schlieren photography has been used to analyse quantitatively the acou stic field of an electromagnetic acoustic transducer (EMAT). By measur ing the angle through which the rays are refracted it is possible to c ompute the refractive index gradient and thus determine both the absol ute and complex pressure related structures of the images. Using this method, planar and focused shock transients generated by the EMAT have been evaluated and compared with transducer derived pressure measurem ents. The peak pressure in the unfocused shock was found to be 3.2 MPa and 4.6 MPa for the Schlieren and piezoelectric transducer measuremen ts respectively. Corresponding values for the focused shock-wave agree d to within experimental error at about 19 MPa.