Diagnostics of laser ablation and laser induced plasmas

A complex diagnostic system is described for the investigation of material ablation by short laser pulses. Besides some conventional measuring methods as microcalorimetry or electrical probes it consists of specially designed equipment such as ballistic microbalance, in situ SEM, high speed microscope coupled with high speed spectroscopy and counterfield energy analyzer. The performance of the diagnostic system is demonstrated for the special case of irradiation of carbon and aluminum by Nd-YAG pulses of medium intensity. The combination of the various techniques enables the quantitative separation of evaporation and particle emission, where the vapor represents only a minor fraction of the ablated mass but carries the main part of the energy. By absorption of laser energy the vapor with energies of some tenth of an eV is transformed to a nearly completely ionized hot plasma of some eV expanding with kinetic energies of some ten eV. In this way the energy and particle balance, the key point for the complex laser ablation process is derived.