| PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES |
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Energetic Ion Effects on the Ion Saturation Current |
| Bin-Bin Lin1,2**, Nong Xiang1,2**, Jing Ou1,2, Xiao-Yun Zhao1,2,3 |
1Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031
2Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei 230031
3School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236037
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| Cite this article: |
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Bin-Bin Lin, Nong Xiang, Jing Ou et al 2017 Chin. Phys. Lett. 34 015203 |
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Abstract The ion saturation current is very important in probe theory, which can be used to measure the electron temperature and the floating potential. In this work, the effects of energetic ions on the ion saturation current are studied via particle-in-cell simulations. It is found that the energetic ions and background ions can be treated separately as different species, and they satisfy their individual Bohm criterion at the sheath edge. It is shown that the energetic ions can significantly affect the ion saturation current if their concentration is greater than $\sqrt {T_{\rm e}/(\gamma_{\rm i2}T_{\rm i2})}$, where $T_{\rm e}$ is the electron temperature, and $\gamma _{\rm i2}$ and $T_{\rm i2}$ represent the polytropic coefficient and temperature of energetic ions, respectively. As a result, the floating potential and the $I$–$V$ characteristic profile are strongly influenced by the energetic ions. When the energetic ion current dominates the ion saturation current, an analysis of the ion saturation current will yield the energetic ion temperature rather than the electron temperature.
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Received: 24 October 2016
Published: 29 December 2016
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| Fund: Supported by the Program of Fusion Reactor Physics and Digital Tokamak with the Chinese Academy of Sciences 'One-Three-Five' Strategic Planning, the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics (NSFC No 11261140328 and NRF No 2012K2A2A6000443), the National ITER Program of China under Grant No 2015GB101003, and the National Natural Science Foundation of China under Grant Nos 11405215, 11475223 and 11505236. |
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