• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.546-551
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• 2024

As an effective methods of plasma heating, neutral beam injection (NBI) systems based on negative hydrogen ion sources will be utilized in future magnetic-confinement nuclear fusion experiments. Because of the collisions between the fast negative ions and the neutral background gas, the positive ions are inevitable created in the acceleration region in the negative NBI system. These positive ions are accelerated back into the ion source and become high energy backstreaming ions. In order to explore the characters of backstreaming ions, the track and power deposition of backstreaming H⁺ beam is estimated using the experimental and simulation methods at NNBI test facility. Results show that the flux of backstreaming positive ions is 1.93 % of that of negative ion extraction from ion source, and the magnet filed in the beam source has an effect on the backstreaming positive ions propagation.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.96.1-96.1
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• 2012

Various electromagnetic fluctuations are observed in the upstream of Earth's bow shock. Properties of plasmas are important in determining the development of the fluctuations. In this study we analyze the phase space distribution functions of plasmas measured by the Cluster spacecraft to understand how the fluctuations develop. Plasmas in the upstream of Earth's bow shock often consist of multiple components, especially when the fluctuations exist. In addition to the solar wind beams, backstreaming ion beams and diffuse ions are also often observed separately or simultaneously. The solar wind beams are not much perturbed even within the fluctuations. The diffuse ions are more than 10 times hotter than the solar wind beams and the backstreaming beams intermediate between them. The distribution functions of the diffuse and backstreaming ions are anisotropic to the magnetic field. Thus, they may be responsible for the fluctuations associated with temperature anisotropy. We will discuss about the thermalization processes and the relationship between the fluctuations and plasmas.