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Measurement of the Density Profile of a Toroidal Non-neutral Plasma with a Wall-Probe Array

Haruhiko SAITOH, Yoshihisa YANO, Tatsunori MIZUSHIMA, Junji MORIKAWA and Zensho YOSHIDA

Department of Advanced Energy, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan

(Received 30 August 2009 / Accepted 3 October 2009 / Published 15 December 2009)

Abstract

The Ring Trap 1 (RT-1) device can confine a pure-electron plasma in the magnetospheric dipole field configuration [Z. Yoshida et al., Plasma Fusion Res. 1, 008 (2006); Y. Ogawa et al., Plasma Fusion Res. 4, 020 (2009); H. Saitoh et al., Plasma Fusion Res. 2, 045 (2007)]. While this system has proved long-term (typically about 400 s) stable confinement, the internal structure of the electron cloud has not been well understood. The spatial distribution of the charge density has been estimated using an array of wall probes. Multiple wall probes with current amplifiers and analog integration circuits were developed and used to estimate image charge profiles on the chamber walls. The electrons are trapped inside the separatrix during the injection phase. In the stable confinement phase, electrons shift toward the stronger magnetic field region and produce a rather peaked profile.

Copyright (c) 2009 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

non-neutral plasma, internal coil device, magnetospheric configuration

DOI: 10.1585/pfr.4.054

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This paper may be cited as follows:

Haruhiko SAITOH, Yoshihisa YANO, Tatsunori MIZUSHIMA, Junji MORIKAWA and Zensho YOSHIDA, Plasma Fusion Res. 4, 054 (2009).