Shock waves and plasma dynamics induced by an open discharge called a ‘‘formed-ferrite-plasma’’ source result in intense radiation from the visible to the vacuum ultraviolet region. An experimental study of both the shock waves and plasma expansions from the ferrite surface has been carried out as a function of electrical energy deposition and of background argon pressure. We show that the propagation of the shock wave is accurately described by the following expression: R=b(E/ρ0)αtn, where R is the distance of the shock front from the surface of the ferrite; E the deposited energy; ρ0 the density of background gas; b, α, and n three constants, and t the time.

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Spectroscopic study of a formed-ferrite plasma source has been carried out in the 115–210 nm spectral region. Emission spectra are dominated either by atomic lines superimposed on continuum emission depending on the surrounding gas. Atomic lines are related to the emission from electronic transitions of singly or multi-ionized atomic species of the ferrite. The electronic density of such a vacuum ultraviolet source is estimated to 4×1018 cm−3 based on Stark broadening effect.

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Résumé : L'hydrodynamique et les propriétés spectroscopiques d'un plasma créé par décharges de surface sur ferrites sont étudiées. Le domaine spectral considéré est celui de l'ultraviolet du vide. Les décharges électriques (200 à 1000 J) réalisées dans de l'argon ou de l'hélium (10~4 Torr à 1,5 bar) conduisent à la formation d'un plasma de forme demi-cylindrique et d'une onde de choc. Nous montrons que leur propagation spatio-temporelle dépend de l'énergie injectée et de la densité du gaz. Les émissions intenses observées entre 115 nm et 220 nm sont attribuées aux particules éjectées de la surface du matériau, à leur interaction avec le gaz environnant, et à l'injection directement dans le gaz, d'une partie de l'énergie électrique stockée.Abstract : Dynamic and spectroscopic characteristics of a vacuum ultraviolet formed ferrite plasma source are presented. Electrical discharges (200 à 1000 J) in argon or helium (10~4 Torr to 1,5 bar) lead to the formation of a halfcylindrical plasma column surrounded by a layer of shock-compressed gas. We show that the plasma and shock wave propagation depends on the deposited energy and on the background gas density. Spectroscopic study in the 115-210 nm spectral region has been carried out. Emission spectra are dominated either by atomic lines superimposed on continuum emission depending on the surrounding gas. Atomic lines are related to the emission from electronic transitions of singly or multi-ionized atomic species ejected from the ferrite.