Abstract

Laser irradiation of a target may be an effective way to initiate phase transitions in the matter, e. g. graphite-diamond transformation during shock loading of a specimen by an ablation pressure. The power density of about 10¹² W/cm² to produce megabar pressure and pulse duration exceeding the time of transformation, i.e. about 100 ns, are needed for such experiments. The spot diameter on a target has to be compared with the extention of a compressed region defined by the product of the front velocity in a specimen and laser pulse duration in order to prevent lateral unloading. It is typically of some hundred microns. By combining these values one can obtain the necessary laser energy of about 100 J. Short-wavelength high-power KrF laser “GARPUN” pumped in a transverse geometry by two counterpropagating relativistic electron beams¹ satisfies well these conditions.

© 1996 IEEE