Large volume, nonequilibrium plasmas at high pressure

Generation, stability, and the general behavior of large volume plasmas at high pressure (p > 10 Torr), have been intensively studied for many years. Applications such as high power lasers, opening switches, plasma processing and sputtering, plasma displays, and EM absorbers and reflectors have motivated detailed works of these phenomena.; Dc, ac or pulsed self-sustained gas discharges are typically used to generate plasmas. Low-pressure self-sustained gas discharges are very stable. In contrast, self-sustained discharges at high pressures are unstable, having a tendency to contract into filamentary plasmas. This transition is known as “the glow to arc instability”.; In this work we demonstrate that a Capillary Electrode System (CES) in a gas discharge suppresses the glow to arc instability and permits the generation of large volume plasmas at high pressure. The CES is assembled by placing a perforated dielectric disk on top of the cathode. Analysis of the pulses of voltage and current across the plasma, along with the light pattern emitted, allows us to verify the mode of the plasma and the absence of instabilities in the range of work. A quantitative analysis was done by looking at the V vs. I curve. Our system allows us to generate non-equilibrium plasmas at atmospheric pressure in volumes of the order of 0.5 liter.; Using a millimeter wave Mach-Zehnder interferometer and lock-in detection we were able to measure effective plasma frequency and effective collision frequency. We use a dielectric model to relate the output values of the lock-in detection to the plasma parameters. In this way, assuming a Maxwellian distribution for the electrons we calculate electron densities in plasmas generated with the CES at high pressures with a sensitivity $Dne$ of 1.0* 107.; Finally, we developed a code using Monte Carlo method to simulate the kinetics of particles in the capillary. This simulation includes elastic and inelastic collisions, ionization, charge exchange, secondary ionization at the electrodes and at the capillary walls and the self-consistent field. As result of this simulation we obtain the field threshold for electron amplification, transport parameters, and the distribution function for capillary plasmas.