Probing pure and mixed neon ECR plasma—An effort for understanding the mechanism of isotope anomaly and gas mixing effect

We report the charge state distributions of the pure and mixed (25%, 50%, and 75% with oxygen and helium gases) neon electron cyclotron resonance (ECR) plasma to probe the hitherto unrevealed mechanism of the gas mixing effect and the isotope anomaly [A. G. Drentje, Rev. Sci. Instrum. 63, 2875 (1992) and A. G. Drentje, Rev. Sci. Instrum. 74, 2631 (2003)]. The multiply charged (up to +7) neon plasma was produced using a 10 GHz all-permanent-magnet NANOGAN ECR ion source. The intensities of highly abundant two isotopes, viz., 20Ne (∼90.48%) and 22Ne (∼9.25%), have been measured by extracting the ions from the plasma, accelerating with different potentials and, finally, analyzing them in mass and energy using a high resolution, large acceptance analyzer-cum-switching dipole magnet. The gas mixing studies show that the addition of oxygen with neon is more effective than that of the helium, particularly on the ion intensities of 20Ne. The higher the fractions of mixing gases, the better are the intensities of highly charged neon ions in the plasma. With and without gas mixing, the intensity ratio of 22Ne to 20Ne shows clear evidence of the isotope anomaly. However, the anomalous effect tends to disappear with increasing oxygen and helium gas mixing. Contrary to the behavior of recently studied pure and oxygen mixed krypton plasma [Kumar et al., J. Mass. Spectrom. 51, 1090 (2016)], the present results are in good agreement with the prediction of linear Landau wave damping theory for selective ion heating in a two-component plasma.