The modified two-dimensional hydrodynamic code POLLUX has been used to simulate the ablation of magnesium, copper, and lead targets in the early stage of expansion (<100 ns) by 30 ns, 0.248 μm KrF excimer and 1.064 μm Nd–YAG lasers at fluences of 3–10 J/cm2. The results of magnesium ablation using KrF laser with different fluences are compared and found to be in reasonably good agreement with the experimental results. A comparative study of laser ablation for magnesium, copper, and lead has been made by simulation using Nd–YAG lasers at fluence 10 J/cm2. The temporal evolution of surface temperature of the target, ablated vapor mass, and ionization fraction of plasma plume is studied for each material. The simulated temporal evolution and spatial distribution of electron density, electron temperature, and axial velocity of ablated plume of each material are studied and the results are compared. It is found that the plume expansion follows adiabatic behavior and is slowed down with increasing atomic mass. In addition to that, the effect of laser wavelength on ablation has also been investigated by comparing ultraviolet KrF excimer and infrared Nd–YAG lasers. It is found that shorter-wavelength lasers favor ablation and plasma screening is more effective for longer-wavelength lasers.
The analytical and numerical results for the slowing down of two heavy projectile ions passing through a multicomponent dusty plasma are presented. Within the linear dielectric approach, the electrostatic potential and the stopping power of the two projectiles are computed for different values of KD (the normalized effective wave number) and R (the separation between the two projectiles) retaining two-ion-correlation effects. The enhancement in the energy loss is observed, and it is compared with that of a single ion projectile case. These results are useful to explain the crystallization of dust grains in astrophysical and laboratory plasmas.
The energy loss of a test charge particle in an unmagnetized dusty plasma is estimated, by incorporating the dust–neutral collisions. A slowly damping large amplitude wake field is observed which moves ahead of the test charge position for large dust–neutral collision frequencies. A critical test charge velocity is determined for a particular dust–neutral collision frequency below which the test charge gains energy instead of losing. The collisions enhance the energy loss only for the test charge velocities greater than the dust acoustic speed.
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