[en] Up to now, the production of plasma columns through the propagation of electromagnetic surface waves had been reported essentially in the microwave range (200MHz-10GHz). It is shown that such plasmas can be achieved at much lower frequencies, at least down to 27MHz. The possibility of operating this plasma both in the RF and microwave frequency range is unique as compared to the other HF produced plasma we know. It allows to optimize the plasma parameters for given applications. We also discuss methods for producing large plasma column diameters and, as an example, characteristics of a 124mm diameter, 3.7 metre long surface wave produced plasma column, are presented

[en] The maximum density of argon atoms in excited metastable states, in a plasma produced by surface wave propagation, is studied experimentally. Measurements are performed by the absorption method, perpendicularly to the tube axis. The measurements show that the maximum population densities of the 3p⁵4s metastable levels in argon are larger in the RF plasma than in the positive column of a glow discharge, between 0.02 and 0.4 Torr in a 26 mm i.d. tube. This fact could be used to improve gas laser operation. (author)

[en] A new way of using electromagnetic surface waves to sustain large volume plasmas of overcritical electron density is described. The diameter of the plasma column, obtained by using the present method, can be relatively large to both the free space wavelength and the dimensions of the wave launcher. (author)

[en] Experimental evidence of parametric excitation, by an intense external H.F. field, of an electron surface mode and an ion wave is presented. The pumping electromagnetic energy density is equal to or slightly larger than the thermal energy density of the electrons. The value of fsub(pe)/f₀ (electron plasma frequency/external field frequency) is that for an electron surface wave. Depending on the pressure and field intensity, this decay instability can lead to three types of low frequency oscillations, with frequencies close to the ion plasma frequency. Two of these are described by ALIEV and SILIN's intense field theory: one is the volume ion plasma oscillation and the other a surface ion plasma oscillation. The third corresponds to no known ion eigenmode. Several other features of the theory by ALIEV and co-workers are also confirmed experimentally, such as the harmonic excitation of the instability (nf₀ approximately fsub(pe)/√2, where n is an integer), the instability amplitude as a function of fsub(pe)/f₀ (above threshold conditions), the value of the mismatch parameter as a function of field strength and ion mass, and the existence of a fine structure corresponding to the symmetric and antisymmetric electron surface oscillations. Even at high pump field strengths, the decay products are nearly monochromatic i.e. the plasma does not become turbulent. (author)

No abstract available

[en] The radial variations of radiative and metastable atom densities in an argon plasma column produced by a microwave surface wave are obtained. A large variety of radial profiles is observed as a function of wave frequency (300-1000 MHz), gas pressure (50-200 mTorr), tube diameter (17.5-34 mm) and axial magnetic field. The results differ significantly from those reported for the dc positive column, where the radial distributions keep approximately the same Jsub(o) Bessel-like profile

[en] Electromagnetic surface waves dissipate energy as they propagate in plasma columns. The transfer of energy to the discharge generally occurs through collisional processes -hence the name ''collisional'' surface waves. It affects the direction of propagation of the wave, and is responsible in particular for the turning back of the axial wavenumber on the phase diagram. The rate of collisions also influences the respective contribution of surface waves and radiation (unguided) waves to the total electromagnetic field. These considerations are of interest in improving the reliability and accuracy of the electron density diagnostic based on surface waves. This paper takes advantage of the many articles published in the domain of guided waves for antennas. (Author)

[en] The inductively coupled plasma (ICP) and the RF capacitive discharges are well known RF discharges that operate in the RF range, at 13, 27 or 40 MHz. The surface wave produced plasma is a possible alternative to these commonly used plasmas that proves to be more advantageous for some applications. Over the past years, the surface wave plasma technology has developed mainly around the surfatron launcher. This device is very efficient (reflected power ≅ 0%), but it remains really compact (axial length < 15 cm) only to the extent that it is used at frequencies exceeding 500 MHz: at 13 MHz, it would typically be 5 meter long. To circumvent this problem, the authors propose the Ro-box launcher, a device that has its launching gap separated from the matching network, in contrast to the surfatron. For frequencies in the range of 200-2450 MHz, the impedance matching is provided by a capacitive coupler (as with the surfatron) and a coaxial tuning stub. In this so-called stub configuration, they show that the Ro-box works as well as a surfatron but it is more compact. For frequencies in the domain 200 KHz-200MHz, distributed L and C impedance components are used. The development work carried out in this low frequency range is reported. It comprises Ro-box power response curves as well as some plasma column properties at reduced pressures and at atmospheric pressures in argon and helium gas

No abstract available

[en] Attenuation of a surface wave is studied experimentally in an unmagnetized cylindrical plasma column sustained by the wave itself. The losses connected with the plasma creation are negligible and the wave propagation is described by the relations for the linear regime. It is shown that a simple theory of collisional attenuation, obtained by extension of the collisionless theory to the case of few collisions, predicts very well the dependence of the attenuation on the electron density, the electron collision frequency, and the geometry of the plasma column. (author)