Ion trapping in dusty plasmas

Summary form only given. A model is developed that includes charge-exchange collisons between ions and neutral gas atoms. The number of trapped ions is computed by assuming a steady state between collisional trapping and detrapping. The trapping rate is the product of a capture cross section and the incoming flux of ions, while detrapping occurs at random times due to collisions with a finite probability per unit time. The results show that the number of trapped ions is independent of the mean free path, and proportional to the plasma ion density. In low-density astrophysical plasmas, it is found that there is no significant number of trapped ions, but in laboratory plasmas, ion trapping can be a major effect that must be accounted for in any dusty plasma theory.