Ionization and Z Effects in Cone Wire Experiments*

In cone-wire experiments, ultra-intense lasers ($>$10$^{18}$ W/cm$^{2})$ are focused at the tip of a cone with a trailing wire attached in order to characterize the cone as a hot electron source for Fast Ignition. Laser pre-pulse simulations predict preformed plasma inside the cone with which the main, ultra-intense pulse interacts. For high Z cones, ionization and Bremsstrahlung significantly alter densities and temperatures of the plasma within half a picosecond. This changes the characteristics of hot electrons generated. The PICLS Particle-in-Cell code has been used to study above-mentioned effects. The model includes laser absorption, dynamic ionization, radiative losses, and particle collisions. Results of PICLS investigations of Z dependence show the dynamics of ionization and Bremmstrahlung within the cone's preformed plasma are complex and must be included when modeling high Z cone targets. *This work performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344 and DE-FG-02-05ER54834(ACE).