Study of the expansion of the laser ablation plume above a boron nitride target

The plasma plume created above a boron nitride target irradiated by a pulsed KrF laser beam is investigated by optical emission spectroscopy and fast intensified camera. The light emitting species detected are B∗, B+∗, N+∗, their velocity varies between 20 and 50 km/s depending on the laser fluence and the ambient pressure in the vessel. The motion of the leading edge is studied under various nitrogen pressures (6 × 10−3 up to 500 Pa) and for two laser fluences (7 and 200 J/cm2) in order to fit the expansion of the front with different models (shock-wave-like and drag force models).