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Jet-assisted sputtering was performed in a conventional Grimm-type glow discharge source (GDS) equipped with a floating restrictor (internal diameter: 8 mm). The source was modified by reversing the gas flow and adding six symmetrically located channels in the restrictor; the channels were directed at an angle of 45° onto the sample surface. The conditions for stable operation were found to not differ from those of a conventional GDS. At power levels below 60 W, the current-voltage characteristics were studied for steel and copper samples; the burning voltages were found to increase by 50 to 300 V when the jet diameters were reduced from 0.5 to 0.2 mm. The resulting burning spots on the sample display the gas-jet pattern. When jets of 0.5-mm diameter were used, electron-microprobe line scans across the burning spots on brass samples revealed no changes in the intensity ratio of Cu/Zn; in contrast, when 0.2-mm jets were employed, composition changes were found, which might be due to analyte redeposition. Under conditions for stable operation, the ablation rates for copper are maximum at 4.77 mg min with a gas-jet diameter of 0.5 mm, a power of 60 W, a gas flow of 210 ml min and a pressure of 532 Pa. In the case of brass, the intensities of copper and zinc lines were found to increase with the sample ablation rate except for the Cu I 324.7 nm resonance line, which presumably suffers self-reversal. Noise power spectra obtained from analyte emission show that in the jet-assisted GDS white noise is predominant. Frequency-dependent components at 10–20 Hz and 60 Hz stemming from the pump and the line, respectively, also occur and are similar to those for a conventional GDS. For the intensities of major element lines the relative standard deviations (RDS) measured at 0.1 s are lower than 0.4%. |
