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An argon-hydrogen atmospheric pressure microplasma jet was constructed for the treatment of materials. The microplasma jet device operating at 50 W produced long plasma jet of 30 mm with gas temperatures measured, using OH emissions, from 1600 to 2600 K as a function of distance. Excitation temperature was found to be from 7000 to 10 000 K. Through the analysis of Hα line broadening mechanisms, surprising hot hydrogen atoms H (n=3) were found with temperatures ranging from 12 000 to 19 600 K.

The electrical breakdown has been investigated for low-pressure argon and nitrogen discharges under the influence of an external longitudinal magnetic field. Plane-parallel aluminum electrodes (5 cm diameter) separated by a variable distance d (4.0 cm < d < 11.0 cm) were sustained with a dc voltage (0 < V < 1 kV). A Helmholtz coil was used to produce an uniform magnetic field(B) parallel to the discharge axis. Paschen curves were obtained and the secondary electron emission coefficient (γ), the first Townsend ionization coefficient (α) and the ionization efficiency(η), were plotted with respect to the variation of the reduced field (E/P). To observe the effect of the magnetic field these curves were plotted for fixed values of B=0 and B=350 Gauss. As consequence of the longitudinal magnetic field, the free paths of the electrons in the Townsend discharge are lengthened and their lateral diffusion is reduced, thus reducing electron losses to the walls. The data presented in this paper give a quantitative description of the B-field effect on the Townsend's coefficients and overall it is concluded that the DC electrical breakdown of the gases is facilitated if a longitudinal magnetic field is applied along the discharge axis.

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