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Author(s):
M. Nishiura, H. Tawara, T. Ido, A. Shimizu1, V.P. Shevelko and LHD experimental group
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Title:
Interactions of intermediate energy Au ions with gases and plasmas: Application to plasma diagnostics
Date of publication:
Aug. 2007
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Key words:
cross sections, tandem accelerator, charge changing process, negative ions, multicharged ions, heavy ions, plasma diagnostics
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Abstract:
The interactions of Au ions with gas and plasma targets are described in details with account for ionization, electron capture and stripping processes for application to heavy ion beam plasma probes (HIBP). A series of the theoretical cross sections for these processes are calculated and are applied to optimize the charge fractions of multi-charged Au (and also Cu) ions at the exit of the tandem accelerator at MeV energy range. In the charge changing processes, the theoretical charge fractions of multi-charged Au ions have been found to behave similarly as the experimental charge fractions under the neutral target areal density of ~ 1x1015 cm-2. These cross sections are also used for estimating the attenuation of MeV energy ion beams in core and edge plasmas of the Large Helical Device (LHD). The signal levels of Au+ and Au2+, which are detected at the primary beam monitor and the energy analyzer, are discussed quantitatively. These results give us some confidence to the enhanced availability of the HIBP system, leading to high precision diagnostics for plasma potentials, their fluctuations, and densities in a thermonuclear plasma. ?
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