Material Dependence of Microwave Emission due to a Hypervelocity Impact

Formerly, microwave emission due to a hypervelocity impact to a metal had been found. The same experiments were carried out for various kinds of material: metal, ceramic, brick and rubber. The waveforms are quite different each other. For an aluminum plate, many pulses are observed in addition to almost continuous generation of random noise in 22GHz-band. For an alumina ceramic, most signal power is in the form of random noise with a small number of pulses. In the cases of a red brick and a polyurethane rubber, a small amount of random noise is observed. The generated power for each material is correlated with electric conductivity and density. The result shows especially that the averaged microwave power has strong correlation with the density. The mechanism of the microwave generation is, therefore possibly related with the destruction process of materials.