diameter of 160 mm situated 25 mm from the anode aperture) was used - Fig. 7b. The solution
conductivity was varied in the range of 5 - 20 mS/cm. The generators have been placed in a
tank where the conductive liquid was separated from the experimental volume containing distilled
water by an acoustically transparent membrane. The pulse power supply consisted of three
condensers 0.5 µF each, charged up to 30 kV and two triggered spark gaps. This arrangement
enables us to produce either a single shock or two subsequent discharges with a variable time
delay. The discharge voltage and current was measured in the same manner as in the corona
discharges. Schlieren photography was used for visualization of the pressure field in the focal
region. Calibrated pressure sensors (PVDF produced by the French company PIEZOTECH S.A.)
with a temporal resolution of 50 ns and with an active area of 1, 4 and 9 mm2 have been used for
measurements of waveforms of the shocks in the focal region. The sensitivity of the probes, as
measured by the producer, is in the range of 22.5 - 24.5 pC/N