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This paper used various geometries to generate cold atmospheric plasma jets: point - plate, multiple points - plate, wire - plate, wire - cylinder. Each geometry was tested with and without a dielectric barrier. Plasma jets were obtained by using high voltage pulses of maximum 30 kV amplitude, and hundreds of nanoseconds width. The pulse repetition frequency was of tens-hundreds of pulses per second. These pulses, applied between electrodes, create discharges in helium or argon filled reaction chamber. The discharge plasma is expelled through a hole, and a plasma jet of several em's long is generated. These devices allow the modification of the interelectrodes distance. The helium/argon flow is in the range of 1-51/min.The electrical, thermal and spectral characteristics of the plasma jets are presented, for each of the used geometries, and for various experimental conditions.The plasma jet temperature is, in any experimental conditions, below 40deg C. By analyzing the plasma jets emission spectra, the concentration of the chemically active species is estimated. This concentration raises by introduction a small amount of chemically active gases (such as oxygen) in the reaction chamber.