Particle tracking on unstructured grids

We report on recent developments and tests of a novel particle tracking algorithm. This algorithm tracks particles element by element through the unstructured grid, stopping and then restarting at each element boundary crossing. Within each element the particles are tracked in the element's local coordinate system. Excellent accuracy is achieved with high order Runge-Kutta integrators despite discontinuities arising from the finite element field solution. Tests on a cylindrical coaxial capacitor meshed with linear, quadratic and cubic tetrahedral elements are presented. The results are compared with a Boris push on a structured grid.