Asymptotic theory of spherical electrostatic probes in large Debye length plasmas containing negative ions

The problem of a spherical electrostatic probe in negative ion containing o xygen plasmas is treated by the matching asymptotic expansions technique [A . H. Nayfeh, Perturbation Methods (Wiley, New York, 1973)]. Assuming that t he energy relaxation length is much smaller than the local characteristic l ength, explicit results are obtained in the asymptotic limits, (r(p)/r(D))( 2)<<1,(r(p)/r(S))(2)<<1, where r(D) is the Debye radius, r(S) is the recomb ination length and r(p) is the probe radius. The perturbation region divide s naturally into a thin space charged sheath, a transitional sheath, and a quasineutral chemically equilibrium plasma. The potential and charged parti cle density distributions are obtained. The calculated probe characteristic is presented in an analytical form. (C) 1999 American Institute of Physics . [S1070- 664X(99)03410-2].