Asymptotic theory of an electrostatic probe in a weakly ionized plasma with negative ions

The problem of a spherical electrostatic probe in a weakly ionized dense pl asma with negative ions is solved by matching asymptotic expansions in powe rs of the small parameters delta = (r(D)/r(p))(2) --> 0 and omega = (r(s)/r (p))(2) --> 0, where r(D) is the Debye radius, r(s) is the recombination le ngth, and r(p) is the probe radius. Account is taken of such kinetic proces ses in a plasma as volume ionization, ion-ion and ion-electron recombinatio n, and electron attachment to electronegative plasma components. It is show n that the plasma perturbed by the probe can be divided into three regions: a space-charge sheath near the probe, a quasineutral inhomogeneous plasma region, and a quasineutral homogeneous plasma region. The profiles of the c harged-particle density and potential are found for each of these regions. The integration constants and the relationships between the boundary condit ions at the probe surface and in an unperturbed plasma are found by asympto tically matching the solutions at interfaces between the plasma regions. Th e electron-energy relaxation length is assumed to be much shorter than the characteristic scale length on which macroscopic plasma parameters vary, so that the electron distribution function is determined by the local values of N-e and T.