Plasma and Fusion Research

Volume 3, 016 (2008)

Regular Articles

Particle Orbit Analysis in the Finite Beta Plasma of the Large Helical Device using Real Coordinates
Ryousuke SEKI, Yutaka MATSUMOTO, Yasuhiro SUZUKI1), Kiyomasa WATANABE1) and Masafumi ITAGAKI
Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
1)
National Institute for Fusion Science, Toki 509-5292, Japan
(Received 6 December 2007 / Accepted 15 February 2008 / Published 22 April 2008)

Abstract

High-energy particles in a finite beta plasma of the Large Helical Device (LHD) are numerically traced in a real coordinate system. We investigate particle orbits by changing the beta value and/or the magnetic field strength. No significant difference is found in the particle orbit classifications between the vacuum magnetic field and the finite beta plasma cases. The deviation of a banana orbit from the flux surfaces strongly depends on the beta value, although the deviation of the orbit of a passing particle is independent of the beta value. In addition, the deviation of the orbit of the passing particle, rather than that of the banana-orbit particles, depends on the magnetic field strength. We also examine the effect of re-entering particles, which repeatedly pass in and out of the last closed flux surface, in the finite beta plasma of the LHD. It is found that the number of re-entering particles in the finite beta plasma is larger than that in the vacuum magnetic field. As a result, the role of reentering particles in the finite beta plasma of the LHD is more important than that in the vacuum magnetic field, and the effect of the charge-exchange reaction on particle confinement in the finite beta plasma is large.

Keywords

finite beta, re-entering particle, LHD, particle orbit

DOI: 10.1585/pfr.3.016

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This paper may be cited as follows:

Ryousuke SEKI, Yutaka MATSUMOTO, Yasuhiro SUZUKI, Kiyomasa WATANABE and Masafumi ITAGAKI, Plasma Fusion Res. 3, 016 (2008).