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Author(s):
T. Takahashi, T. Kato, N. Iwasawa and Y. Kondoh
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Title:
Power Deposition by Neutral Beam Injected Fast Ions in Field-Reversed Configurations
Date of publication:
Apr. 2004
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Key words:
Field-Reversed Configuration, neutral beam injection, Monte Carlo method, slowing down collision, power deposition, non-adiabatic motion
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Abstract:
Effects of Coulomb collisions on neutral beam (NB) injected fast ions into Field-Reversed Configuration (FRC) plasmas are investigated by calculating the single particle orbits, where the ions are subject to the slowing down and pitch angle collisions. The Monte-Carlo method is used for the pitch angle scattering, and the friction term is added to the equation of motion to show effects of slowing down collision such as the deposited power profile. Calculation parameters used are relevant to the NB injection on the FRC Injection Experiment (FIX) device. It is found that the dominant local power deposition occurs in the open field region between the X-point and the mirror point because of a concentration of fast ions and a longer duration travel at the mirror reflection point. In the present calculation, the maximum deposited power to the FRC plasma is about 10 % of the injected power. Although the pitch angle scattering by Coulomb collision destroys the mirror confinement of NB injected fast ions, this effect is found negligible. The loss mechanism due to non-adiabatic fast ion motion, which is intrinsic in non-uniform FRC plasmas, affects much greater than the pitch angle scattering by Coulomb collision.
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