Underwater spark discharge has been extensively studied in connection with the development
of the so-called extra-corporealshock wave lithotripsy, a noninvasive method for treatment
of kidney stone disease [9]. High voltage/high current spark discharge between needle electrodes
in water provides a point-like source of strong shock waves. If the discharge is situated
in the focus of a semi-ellipsoidal metallic cavity, the wave energy is concentrated in the secondary
focus. The interaction of the focused shock wave with the kidney stone positioned in the
secondary focus results in crushing the stone into small particles that naturally leave the patient
body. Formerly, we have developed a generator of focused shock waves with the spark discharge