When powerful radiation bursts interact with solid targets the ejected material escapes in a peculiar sheet-like form with hyperthermal velocity. An attempt is made to explain this phenomenon by the action of a thermomechanical shock wave which is generated in the target and ejects the heated surface layer with twice the particle velocity of the shock. The theory has been tested for electron pulses for which a simple one-dimensional approach is possible. Extension of the presented theory to laser pulses gives the proper order of magnitude for the plume velocity and other observed phenomena.

A stress-wave system of three intersecting waves may be generated by electron-pulse techniques. The waves intersect at an angle of 90° and cause a brittle mode of fracture in the superposition interval in otherwise ductile metals. Fractographic investigation shows a peculiar type of intergranular fracture in which individual grains are separated and rotated. Fracture occurs simultaneously at a multitude of locations where the acoustic impedance between individual grain boundaries is sufficiently large.

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