J. Marec

Axial electron density and wave power distributions along a plasma column sustained by the propagation of a surface microwave

The propagation of electron surface waves can be used to sustain long plasma columns. The relation between the axial distribution of the electron density observed along the plasma column and the corresponding power distribution of the surface wave that produces it is investigated. It is found that the electron density decreases almost linearly along the plasma column in the direction of the wave propagation. This is explained by assuming that the number of electrons produced over a given axial length is proportional to the wave power absorbed over that same length.

Influence of the excitation frequency on surface wave argon discharges: Study of the light emission

We compare discharges produced by surface waves at 210 MHz and 2.45 GHz in argon at low pressure (0.1–10 Torr). For plasma lengths up to 1 m, the plasma and wave characteristics are determined (electron density, electric field, effective collision frequency, etc.) and the influence of the excitation frequency is shown. Studying the emission of the discharge, we have established relations between the intensities of Ar i and Ar ii lines and these characteristics, taking into account the wave frequency. That leads to practical criteria for the choice of the excitation frequency.

Action of a static magnetic field on an argon discharge produced by a traveling wave

This paper deals with a low‐pressure argon microwave discharge (5–100 mTorr), created and sustained by a traveling wave (390 MHz), in the presence of an axial static magnetic field (up to 550 G). First, the propagation characteristics of the wave (wave number, wave collisional damping, radial distribution of the electromagnetic energy) have been computed from the numerical resolution of the dispersion equation. It has been emphasized that the plasma is sustained either by a surface wave, or by a volume wave, according to the electron density and magnetic field values. Second, the electron density, the effective electron‐neutral collision frequency ν for momentum transfer, the mean power θ required to maintain an electron in the discharge, and the effective electric field Eeff for the discharge maintaining have been experimentally determined, versus the pressure and the magnetic field. At a fixed pressure, the power required to maintain the discharge decreases as the magnetic field increases. It has been s...

Microwave plasma in argon produced by a surface wave: study of the effect of pressure on the optical emission and the potentials for analysis of gaseous samples

Abstract The possibility of chemical analysis of gaseous samples by optical emission spectroscopy has been evaluated using a microwave induced plasma created by a surface wave at 210 MHz. Methane has been introduced at low concentration (1–20 ppm) in argon gas. The emission of excited CH, CN, C2 at atmospheric pressure, was observed along the discharge and studied as a function of the methane concentration. The influence of the pressure on CH emission is presented from 10 Torr to atmospheric pressure. Contrary to usual predictions, the emission of CH bands is maximum at about 100 Torr and not at atmospheric pressure.

Electron density determination using phase measurement in a pulsed surface wave discharge at high pressure

This paper deals with the determination of electron density in a pulsed surface wave discharge (frequency ω/2π=1.1 GHz, pulse duration τ∼10 μs), in an air‐like mixture at about 10 Torr in a capillary tube (inside diameter 1.5 mm). A time‐resolved diagnostic based on microwave interferometry is developed. It is shown that it provides both the collision frequency ν and the electron density ne except when ν/ω exceeds a certain value (5 for these operating parameters).

Efficient pulsed microwave excitation of a high‐pressure excimer discharge

We report on a microstrip line structure able to sustain plasmas up to five bars of a He/Xe/HCl mixture, with good stability and reproducibility and without preionization of the mixture. The microwave power coupling has been characterized and the incoherent ultraviolet‐308 nm emission has been studied by means of time‐resolved spectroscopy.

Rotational and Vibrational Temperature in a Pulsed Microwave Air Discharge

Rotational and vibrational temperatures have been measured by time-resolved optical emission spectroscopy in a pulsed surface wave discharge in airlike mixture. For a wave frequency of 1.1?GHz, a pulse length of 4.5??s and a peak power of 20?kW the temperatures are increasing by a factor of 3 during the first ?s. These variations certainly have a great influence on air breakdown.

Low-Pressure Argon Discharge Sustained by a Wave with an External Applied Magnetic Field

We have experimentally studied the action of a static magnetic field on a low-pressure argon discharge created and sustained by a travelling wave. We have determined the electron density and the discharge characteristics (effective electron neutral collision frequency, discharge sustaining power). It appears that the decrease in the discharge sustaining power with an increasing magnetic field can be described by a simple variation law.