The effect of plasma shielding on dust particle interaction in low pressure plasmas

The interaction of charged dust particles in plasma is often modeled assuming a constant charge on each particle with the particle charge determined by requiring zero net current to the particles when they are far apart. In this paper the variation in particle charge is calculated for two-body encounters of dust particles taking into consideration mutual electrostatic shielding and a finite Debye length λ_D. Results are reported for particle radii between 0.0105 λ_D and 0.349 λ_D. Work is also calculated as a function of particle separation, and it is shown that dust-particle energies greater than 50 eV are required before the variation in charge becomes significant. It is also demonstrated that for particles with radii greater than λ_D/10 the plasma can act to increase the force at separations less than 3 λ_D, and it is shown that the Debye-Hückel factor ( 1 + a/λ _D ) may overestimate particle charge by as much as ten percent for larger particles.