Generation of plasma in low-pressure discharge

A hydrodynamic model of plasma has been developed, which takes into account both secondary and primary electrons. It has been shown that a solution with a plasma potential higher than the anode potential is possible if the ionization frequency is higher than some critical value. At lower ionization frequencies, it is possible to obtain a solution with a plasma potential below the anode potential

Low-frequency temperature-dependent plasma discharge instabilities in the presence of external constant electric and magnetic fields

By calculating the dielectric permittivity of a magnetoactive plasma discharge in the presence of an external electric field, low-frequency instabilities resulting from the dependency of the electron-neutral collision frequency, electron-ion recombination coefficient and ionization frequency on the electron temperature are investigated. Furthermore, it is shown that some of these instabilities depend on the sign change of the derivative of the kinetic coefficients with respect to the electron temperature. Finally, it is shown how frequency spectra and the development of instabilities are changed by increasing the strength of the external magnetic field.

Two-dimensional simulation of initiation and evolution of a plasma channel in the XeCl laser pumping discharge

We present two-dimensional simulation results of the formation and evolution of a diffuse plasma channel in the XeCl pumping discharge. Channel formation was initiated by metallic convexity at the cathode surface with a characteristic dimension of ∼0.1 cm. Two pumping regimes were considered. Initial voltage in the second regime was increased 1.6 times and impedance was decreased 2 times in contrast with the first regime. Evolutions and spatial distributions are presented for electron density, electric field, and frequencies of the main process. In the first regime, the diffuse plasma channel forms. The main processes causing development of the plasma channel are inhomogeneous distribution of the electric field, increase of the stepwise ionization frequency at ne ∼ 1015 cm−3, and depletion of HCl. Increasing of the initial voltage and decreasing of the impedance in the second regime results in a quick rise of the discharge current and electron density in the discharge gap, and uniform discharge takes place during the current pulse.

Nanosecond air breakdown parameters for electron and microwave beam propagation

Air breakdown by avalanche ionization plays an important role in the electron beam and microwave propagations. For high electric fields and short pulse applications one needs avalanche ionization parameters for modeling and scaling of experimental devices. However, the breakdown parameters, i.e., the ionization frequency vs E/p (volt. cm−1. Torr−1) in air is uncertain for very high values of E/P. We review the experimental data for the electron drift velocity, the Townsend ionization coefficient in N2 and O2 and develop the ionization frequency and the collision frequency for momentum transfer in air. We construct the E/p vs Pτ diagram and show that our results are in better agreement with the most recent short pulse air breakdown experiments, compared to those predicted by the expression of Felsenthal & Proud (1965). This is because they extrapolate an expression for the drift velocity, linear in E/p, to high values of E/p. Experimentally the drift velocity varies as (E/p)½ in the region of E/p > 100.