Calculations of the forces experienced by particles in high density plasma sources such as an electron cyclotron resonance system indicate that particles can accelerate in the plasma and travel through sheaths. This is due primarily to the very high ion fluxes in these systems and relatively low sheath potentials. The net result is less particle trapping and growth in the plasma compared to conventional plasma sources. The temperature of the particles is calculated from an energy balance. The particles heat due to electron‐ion recombination on their surface, and they cool by radiation and conduction to the neutral gas. Because of the high plasma density and low neutral pressure, the particles may reach high temperatures (T∼1000 K).