Effect of small amounts of hydrogen added to argon glow discharges: hybrid Monte Carlo-fluid model

Tungsten Molecular Species in Deuterium Plasmas in Contact with Sputtered W Surfaces

We show that in plasmas generated in deuterium in the presence of sputtered W surfaces, various molecular tungsten species are formed, whose chemical composition depends on the presence of gaseous impurities, namely, nitrogen, oxygen, and hydrogen. A magnetron discharge was used for plasma sustaining, and the species were investigated by mass spectrometry and optical emission spectroscopy. The identified tungsten-containing molecules are described by the chemical formula WOxNyDzHt, where x = 0-4, y = 0-3, z = 0-3, t = 0-5. Presumptively, even higher mass tungsten molecular species are present in plasma, which were not detected because of the limitation of the spectrometer measurement range to 300 amu. The presence of these molecules will likely impact the W particle balance and dust formation mechanisms in fusion plasmas.

Nitrogen effects in multi-matrix calibrations by radiofrequency glow discharge – optical emission spectrometry

A study about the effect of nitrogen in the calibration curves of a series of analytical emission lines has been carried out in this work. Fifteen reference materials with different matrices (Fe, Al, Zn, Cu and Ni) were used (three of these reference materials contain nitrogen in their composition) and plots of intensity versus the product "sputtering rate times element concentration" were constructed for emission lines of the analytes considered in this work (Al, Fe, Cu, Cr, C, Mo, Zn, Si, Ti and Ni). Two different fits were performed in each plot, first considering only the points corresponding to samples without nitrogen in their composition and secondly including all the points. The results show almost negligible differences in the emission yields calculated. On the other hand, a mixture of Ar containing 0.5% N2 was employed to check if the nitrogen effect was present at higher concentrations than those expected in analysis when samples with high nitrogen concentrations are used. Differences between the slopes of the calibration curves with the Ar/N2 and pure Ar discharges were obtained (up to 30%). A study of the molecular bands recorded in the spectra when nitrogen is present in the discharge and determination of the resulting interferences on the analytes have been performed.

Moment Theory of Ion-Neutral Reactions in Traps and Similar Devices

Recent moment theories of ion motion in traps and similar devices are extended to mixtures of neutral gases in which one or more components can undergo infrequent reaction with the ion of interest. Expressions are developed for the position and time dependence of the ion-neutral reaction rate coefficient in such circumstances. These expressions are incorporated into the sets of coupled differential equations that govern the average ion velocity and kinetic and internal energies. This provides a consistent description of the ion transport and reaction coefficients.