Composition of Positive Ions in High-Density H2 Plasmas Measured by Time-of-Flight Mass Spectrometry

概要

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The composition of positive ions, H+, H$_{2}^{+}$, and H$_{3}^{+}$, in high-density H2 plasmas was measured using a time-of-flight mass spectrometer which was attached behind the end plate of a linear helicon-wave plasma source. The dominant ion was H$_{3}^{+}$ when electron density was below $3.5\times 10^{11}$ cm-3, while in high-density plasmas with $n_{\text{e}}\geq 8\times 10^{11}$ cm-3, H+ and H$_{2}^{+}$ were dominant at similar fractional abundances. In the afterglow plasma, the fractional abundance of H$_{2}^{+}$ decreased rapidly with a time constant of ${\sim}3$ μs. Simultaneously with the disappearance of H$_{2}^{+}$, H$_{3}^{+}$ became dominant in the late afterglow. The above experimental results were examined by a rate equation analysis based on available reaction rate coefficients. The results of the rate equation analysis were qualitatively consistent with the experimental observations.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-11-15