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takahashi_presentation.pdf2011-08-19 11:36:23Toshiki Takahashi
proceeding.pdf2011-08-14 16:49:45Toshiki Takahashi

Toroidal spin-up due to electron fluid fluctuation of a field-reversed configuration

Author: Toshiki Takahashi
Requested Type: Consider for Invited
Submitted: 2011-06-08 21:37:52

Co-authors: F.P.Iizima, T. Asai

Contact Info:
Gunma University
1-5-1 Tenjin-Cho
Kiryu, Gunma   376-851
Japan

Abstract Text:
The rotational instability with the toroidal mode number n=2 of a field-reversed configuration (FRC) plasma is the most often observed global instability. The FRC current just after formation is primarily carried by electron current, while ions are approximately at rest. The ions, however, gradually gain angular momentum in the ion diamagnetic direction before the onset of the instability. Rotation of the FRC plasma has been often explained by selective loss of ions, or end-shorting, or both.
We have proposed another possible spin-up mechanism, which is direct conversion from the magnetic flux to the kinetic angular momentum as long as axisymmetry holds. Conversion to the angular momentum, however, also occurs for electrons, and it plays the electron current drive and consequently maintains the magnetic flux.
Therefore, we suppose that the presence of an anomalous loss of the electron angular momentum due to an electron fluid fluctuation with higher frequency than the ion cyclotron frequency. Spatial structure of the fluctuation in an FRC is studied analytically. Calculation of electron orbits in the prescribed fields is carried out in order to find the loss of the angular momentum, i.e., the resistivity. We also run an electron particle simulation to compare results to those from our analytical model.
We will summarize our findings so far on the toroidal spin-up and preliminary results of the electron fluid fluctuation in an FRC.

Characterization: A7,D5

Comments:

University of Washington

Workshop on Innovation in Fusion Science (ICC2011) and
US-Japan Workshop on Compact Torus Plasma
August 16-19, 2011
Seattle, Washington

ICC 2011