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A new technique has been developed to generate an extremely high impulsive pressure by using an explosive. A metal jet, typically observed in explosive welding is used in this technique. The behavior of metal jet is crucial to the design of pressure generator. The experimental observation was made by the collision of metal jet on a metal block surface. Many craters formed by the collision of metal jets on the surface of the metal block were observed. The craters were overlapped and distributed in a wide range. The diameter of the largest crater was 0.5 mm. The quantity of the discharged metal jets was found to be a function of the quantity of explosive. The total area of the craters is considered as proportional to the quantity of the discharged metal jets and the experimental conditions for the formation of large craters was investigated.

The various techniques of phase transformation of the material have been proposed by many researchers. We have developed several devices to generate the ultrahigh pressure by using high explosive. One of them uses metal jets. It is expected that the ultrahigh pressure occurs by the head-on collision between metal jets, because the velocity of the metal jet is very high. By mixing a powdered material with metal jets, the pressure of the material becomes high. The purpose of this study is to transform the phase of the powdered material by using this high pressure. The powders of the graphite and hBN were applied. The synthesis to the diamond and cBN was confirmed by X-ray diffraction (XRD). In this paper, the mechanism of the generation of the ultrahigh pressure is explained and the results of the observation of the powder by using scanning transmission electron microscope (STEM) are reported.

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A method to generate an extremely high impulsive pressure using a converging metal jet, has been developed as a purpose to achieve the high pressure above 1 TPa. The metal jet is discharged from the collision point, when a metal plate is accelerated by the detonation of an explosive and it collides with a conical concave metal block. The metal jet discharged on the concentric circle of the conical concave fly toward the center while converging and collide on the central axis, and the collided metal jets exhibit the extremely high pressure. In the present investigation, framing photographs were taken using an image converter camera to investigate the phenomenon occurred in the generator. The photographs show that the metal jets are discharged from the collision points between the metal flyer plate and conical concave block, and then, collided at the central axis. The maximum pressure obtained under vacuum was estimated about 0.83 TPa from the velocity calculated from the photographs, and the results were slightly lower than that evaluated theoretically.