Acoustic pulse magnification at its propagation along structurally-modifed zone of radiation-matter interaction

Summary form only given. The acoustic emission caused by a high-current tubular electron beam in rod polycrystalline metal samples was experimentally studied. Two zones of beam-rod interaction emitted equal thermoacoustic pulses, those propagated along the rod body to acoustic detectors connected to each of free butt-ends of the target. Despite equal generation conditions, the second pulse arrived at the detector before the first one. Such a phenomenon is possibly connected with incomplete relaxation of residual thermoelastic stress in irradiated metal over the time interval between two pulses passing. The first pulse comes to detector passing through nonirradiated material, whereas the second one passes through radiation-modificated zone on its way to the detector. Herewith the variable stress breakaways dislocations from stoppers are causing coherent acoustic emission from the structurally-modified zone that amplifies the propagating pulse. The investigations show clearly the presence of a nonthermoelastic component in generated stress wave. A deposit of bulk expansion due to phase structural transitions in radiation-acoustic effect may exceed significantly that from thermal expansion. Some modification of radiation-acoustic equations providing an account of the phase transitions are discussed.