Parametric study on absorption process for high-power laser irradiation of aluminum with robust collision frequency model

Due to the improvement and sophistication of laser technologies in the last several decades, high-energy–density plasma (HEDP), which were only attainable in extreme environments such as stellar interiors and nuclear explosions, can now be generated in laboratory scale via laser–target interactions. This breakthrough in technology has made HEDP research more accessible, and thus active studies on HEDP have been ongoing. In this work, laser energy absorption is investigated in the context of laser–target interactions. Because energy absorption in laser–target interactions is mediated by collisional processes like inverse bremsstrahlung, an accurate modeling of the collision frequency between electron and ion is crucial. However, depending on the laser configurations, the target undergoes transformation from solid to warm dense matter (WDM), and then to hot dense plasma, and the collisional behaviors are considerably different for each material state. In order to address this issue, a new, versatile, and robust collision frequency model was proposed by interpolating the models for solid state and for hot dense plasma. An extensive numerical calculation was conducted using a 1D radiation hydrodynamics code (MULTI), and a wide range of values for each laser parameter (laser intensity, pulse duration, and wavelength) is examined. The dependencies of the laser energy absorption, as well as the temporal dynamics of laser energy absorption process, on each laser parameter are presented.