Benchmarking the Democritus code

Summary form only given. The DEMOCRITUS code is a particle-based code for plasma-material interaction simulation. The code makes use of particle-in-cell (PIC) method to simulate each plasma species, the material, and their interaction. In this study, we concentrate on a dust particle immersed in a plasma. We start with the simplest case, in which the dust particle is not allowed to emit. In this case, we are only concerned with the primary currents, I_e and I_i. We examine several parameters, including the charge and potential of the dust particle. The code is then benchmarked against theory using MATLAB to calculate the steady-state potential and charge on the dust particle. Next, we expand the DEMOCRITUS code to include thermionic and photo emission algorithms. We then find the equilibrium floating potential and charge on the dust, which now can be positive as a consequence of electron emission. We benchmark against our MATLAB theory, where we make use of the primary currents as the sources and the thermionic emission current, I_th, and the photo emission current, I_pe, as the sinks. Finally, we use our MATLAB benchmarking script to compute the ion and gas drag forces, as well as to solve Newton´s equation for the grain. From this, we obtain the time history of the grain motion and compare with the results obtained from the DEMOCRITUS code