Dynamics during pulsed laser ablation of high T/sub c/ superconductor

The ablation of high critical temperature (T/sub c/) YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting bulk (1-mm thickness) by a nanosecond-pulse KrF excimer laser ( lambda =248 nm) is studied numerically. The dynamics of ablation is simulated by solution of the one-dimensional heat flow equation. The finite-element method is applied to solve the equation, including the temperature dependence of the thermal conductivity of the bulk, the movement of a vapor-liquid interface, the latent heat of melting and ablation, and the energy of the laser-generated plume. The melting threshold energy density is found to be 0.08 J/cm/sup 2/, and the ablation threshold energy density is estimated to be 0.22 J/cm/sup 2/. The mean velocity of the laser-generated plume increases with the increase of laser energy density from 0.93*10/sup 4/ m/s (2 J/cm/sup 2/) to 1.95*10/sup 4/ m/s (10 J/cm/sup 2/).<
>