Collisionless orbit theory is used to model isolated particles in low-pressure discharges with and without the presence of negative ions. The key results are as follows: (1) Debye–Hückel theory works well for approximating the potential profile around the particle, and (2) the size of the sheath around the particle is determined by a Debye length that results from linearizing the Poisson–Vlasov equation. These results are valid as long as the ratio of particle radius to Debye length is small and the ratio of Debye length to mean free path is small.

Classical scattering theory is used to calculate momentum-transfer cross sections between positive ions and isolated particulates in glow discharges for several model particle sheath potentials. Cross sections calculated from a potential profile obtained using self-consistent orbit (Poisson–Vlasov) theory, an attractive screened Coulomb potential, and an attractive cutoff Coulomb potential are compared. At high ion energies, all model potentials result in the same cross-section dependence on ion energy. At low ion energies, however, the cutoff Coulomb potential gives a cross section too low by about a factor of 10. The screened Coulomb potential and Poisson–Vlasov theory potential result in momentum-transfer cross sections equal to within 30% over the entire range of ion energies. An approximate analytic expression for the momentum transfer rate coefficient is given for order of magnitude estimation of the ion drag force.

High densities of submicron particles have been created in an Ar/SiH4 parallel plate radio-frequency (rf) discharge. The particles were collected and measured by electron microscopy and the mean particle diameter was found to be 230±60 nm. Laser scattering from the dense clouds of such particles showed that the concentration was 1×108 cm−3. A laser Doppler anemometer was used to measure the particle velocity distribution and hence the mean particle mass. This is consistent with the specific density of the hydrogenated amorphous silicon. The mean velocities of particles were measured at two different gas flows when the discharge was extinguished, so that the particles are neutral and do not interact, and the particles move with the gas velocity. However, during the discharge the particles have almost no mean axial velocity, even though the gas flow is as large as before. This is due to the strong interparticle interactions that keep the particle cloud, as a whole, stationary. The charge on the particles is estimated, leading to a value of the Coulomb coupling parameter of Γ=10. This large value suggests that the particle cloud can be viewed as a Coulomb liquid.

Magnetized argon plasma columns with peak densities of greater than 1018 m−3, lengths of 2 m, and full width half-maximum diameters of 0.3 m have been created at pressures of 40 mPa (3×10−4 Torr) with input powers of 1.5 kW of 7 MHz rf.

A two-dimensional, axisymmetric model of a bounded, partially ionized, magnetized glow discharge plasma has been developed. The model treats positive ions as particles and electrons as a fluid in a hybrid configuration. The results reported here are directed towards simulating an electron cyclotron resonance (ECR), microwave-sustained plasma. Microwave power profiles in the plasma are assumed. and the resulting electron and ion transport in the applied magnetic? and selfconsistent electrostatic field is calculated. Sheaths under typical operating conditions are very thin and we apply an analytic sheath model to avoid integration in the sheaths. Typical results are presented for a common ECR reactor geometn, and conditions, and comparisons with experimental data are made when possible.