In current and next day large tokamaks with carbon-based plasma-facing materials, carbon ions and many kinds of hydrocarbon molecules as well as another impurities exist in their edge and divertor plasmas [1]. For understanding the impurity behavior, cross section data for charge transfer processes of these ions with molecules are required.
In this work, we have measured the single- and double-charge transfer cross sections of C²⁺ ions in collisions with CO, CO₂, and various hydrocarbons in the energy range between 0.70 and 6.0 keV. The doubly-charged carbon ions were extracted from a compact electron beam ion source called micro-EBIS [2] using a strong ring permanent magnet. The cross sections of charge transfer were determined by the initial growth rate method.
Most of the present single- and double-charge transfer cross sections are found to show weak energy dependence over the collision energy range observed. The single-charge transfer cross sections for hydrocarbons depend on the first ionization potential of target molecules. On the other hand, for the double-charge transfer cross sections, such simple dependence on the first ionization potential cannot be found. While fairly good systematic dependence of the double charge transfer cross sections are found on total number of electrons, number of bonds and poralizability of target molecules.

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