Grid-free tree-code simulations of the plasma-material interaction region

A fully kinetic grid-free model based on a Barnes-Hut tree code is used to selfconsistently simulate a collisionless plasma bounded by two floating walls. The workhorse for simulating such plasma wall transition layers is currently the PIC method. However, the present grid-free formulation provides a powerful independent tool to test it [I] and to possibly extend particle simulations towards collisional regimes in a more internally consistent way. Here, we use the grid-free massively parallel Barnes-Hut tree-code PEPC - a well established tool for simulations of Laser-plasmas and astrophysical applications - to develop a 3D ab initio plasma target interaction model. With our approach an electrostatic sheath naturally builds up within the first couple of Debye lengths close to the wall rather than being imposed as a prescribed boundary condition. We verified the code using analytic results [2] as well as ID PIC simulations [3]. The model was then used to investigate the influence of inclined magnetic fields on the plasma material interface. We used the code to study the correlation between the magnetic field angle and the angular distribution of incident particles.