Density-conserving shape factors for particle simulations in cylindrical and spherical coordinates

It is shown that, in cylindrical and spherical coordinates, particle-to- grid weighting based on conventional particle-in-cell (PIC) and cloud-in-cell (CIC) shape factors results in non-uniform grid densities even for uniform particle distributions. Instead, alternative, density-conserving weighting schemes are discussed, including modified PIC and CIC weighting. 10 refs., 5 figs.