This article presents a new theoretical model of ion collection by a cylindrical Langmuir probe at medium and higher pressures which we call the "modified TALBOT and CHOU model". The model makes use of the following theories; (a) the kinetic theory by CHOU, TALBOT and WILLIS [6, 71 and (b) the theory by ZAKRZEWSKI and KOPICZYNSKI [lo, 1 I]. The basic idea is to calculate the decrease of probe ion current due to collisions with neutrals according [6, 71 and the increase of the ion current due to destruction of an orbital motion according [lo, I I]. The computed results are presented in the form of graphs suitable for probe data interpretation at medium and higher pressures. The applicability of the results at particular plasma conditions is also discussed.

The description and investigation of a new atmospheric plasma source for the treatment and coatings of surfaces are presented in this paper. This new system is a modification of a well-known atmospheric torch discharge stabilized by a flowing channel of the working gas through an RF powered nozzle. The new version of this source prevents the transition to the regime with hot electrodes. This modification is suitable for surface and coatings applications of such substrates sensitive to overheating causing undesirable phase transition or melting. The new source called in our paper as an RF barrier-torch atmospheric discharge employs dielectrically coated nozzles instead of bare metallic ones. In that case, the plasma jet has quite different properties, as it is clear from presented experiments. The new version allowed excitation of the atmospheric plasma channel interacting with the substrate independently on the conductivity of the substrate. Simultaneously it is possible to hold the substrate temperature under atmospheric jet interaction below the limit point of aluminium melting or below an even lower limit of 80˚C in a pulse-modulated mode. Extension to the multi-nozzle barrier-torch system was attained with the application of nine quartz nozzles. This multi-plasma jet excitation and its interaction was demonstrated with the substrate made of either quartz or aluminium plate, both possibly with non-flat shape. Emission spectroscopy and RF voltage and current amplitude measurements were employed in order to characterize the RF barrier-torch discharge.

Eighty years have passed since Langmuir's first use of the word 'plasma' for describing ionized media. On this occasion we would like to present selected recent results on the application of Langmuir probes to diagnose plasma jet systems. To demonstrate the versatility of the Langmuir probe method we give examples of measurements of the spatial distribution of the plasma parameters as well as their temporal dependence in cases when the plasma jet system operates in a pulsed regime. A part of this paper is devoted to introducing the Langmuir probe technique, especially with regard to its application under conditions when collisions between the charged and neutral particles in the probe sheath cannot be neglected and when the electron energy distribution function in plasma cannot be approximated by a Maxwellian one. In the experimental part we present Langmuir probe measurement of low-pressure and atmospheric-pressure plasma jet systems that are currently used for experiments with deposition of materials with special properties.Most of the experimental results presented in this paper are original data. However, in order to fill in the picture we have used in the case of a barrier-torch discharge three figures that have already been published.