An explosive configuration was studied so that the underwater shock wave converges at the tip of the explosive, and a three-dimensional spiral configuration was obtained. This spiral configuration need to be analyzed theoretically due to the relation of propagation velocity of underwater shock wave, detonation velocity of the explosive and a configuration of vessel to charge the explosive. In order to study an effect of the convergence, pressure measurement at the spiral center was carried out by using a manganin gauge. Therefore, when SEP was used in this experiment, the maximum pressure value was 17.7 GPa. This maximum pressure value is higher than the pressure value of underwater shock wave generated from the underwater explosion of a straight configuration. Furthermore, this maximum pressure value was higher than C-J pressure of SEP. An initial pressure of underwater shock water shock wave that can obtain from an isentropic expansion curve of SEP and a characteristic curve of water is 5.7 GPa, and C-J pressure of SEP is 15.9 GPa. From the above-mentioned, the effect of spiral convergence could be shown well.

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