High-Density Plasma Laser Interaction

Abstract

High-density plasmas are of interest for fundamental research and applications, as e.g., in light sources and fusion, as well as for the understanding of the physics in stellar and planetary systems. In recent years, ultra-short high-intensity laser pulses have become available so that intensities up to 10 W/cm can be reached. New facilities are under construction which produce radiation of frequencies up to theX-ray regionwith high brilliance. This radiation is used to produce plasmas over a wide range of density, pressure and temperature, as well as subsequently to probe its properties. Dimensionless quantities can be introduced to characterize the properties of the plasma near equilibrium: the degeneracy parameter 1⁄4 kBT=EF 1⁄4 2mekBTð3pneÞ 2=3 h 2 is the ratio of the electronic temperature to the Fermi energy. For 51, the plasma has to be treated as a quantum system. The coupling parameter 1⁄4 Vei=kBT 1⁄4 ð4pne=3Þeð4p 0kBT Þ 1 characterizes the size of the interaction potential at the mean distance of the electrons with respect to the thermal energy. At high densities or low temperatures ( > 1), the plasma is strongly coupled and correlations and collisions have to be taken into account. Hot and dilute systems are weakly coupled and can be treated perturbatively. Relativistic plasmas, in which a significant part of the electrons reaches a speed close to the speed of light, can also be produced leading to new theoretical and experimental challenges, e.g., about 10% of the electrons in a thermal plasma of T > 260 keV have a speed of 0.86c. Very promising issues are, e.g., the creation of high-energy quasi-monoenergetic electron and ion beams [1] or the investigation of nuclear reactions triggered by laser-accelerated relativistic electron jets [2]. An important question in almost all experiments with interaction of intense laser pulses with matter is the calculation of the energy deposition and the description of the subsequent heating. After the laser field has delivered