[Table of Contents]

Plasma and Fusion Research

Volume 2, S1091 (2007)

Regular Articles

Measurement of Electron Density and Temperature and Their Fluctuations Using Modified Triple Langmuir Probe Grounded through Finite Resistance
M. TAKEUCHI, K. TOI1), R. IKEDA, C. SUZUKI1) and CHS EXPERIMENTAL Group1)
Department of Energy Engineering and Science, Nagoya University, Nagoya 464-8603, Japan
1)
National Institute for Fusion Science, Toki 509-5292, Japan
(Received 5 December 2006 / Accepted 23 April 2007 / Published 20 November 2007)

Abstract

In the triple Langmuir probe (T-LP) method, the electron temperature (Te) and density (ne) can be simultaneously derived from potential measurements of electrode of T-LP and the ion saturation current (Iis) where no current flows in the electrodes for potential measurements. In the case of aiming at measuring high-frequency fluctuations, however, the smaller load resistance of electrode is required for high frequency response. Then the finite current can flow in the measurement circuits of the floating potential (Vf) and the plus-biased potential (Vp). When the current becomes comparable to Iis, the Te derived from measured Vf and Vp without the current considerably deviates from an actual value. This would be significant for fairly low density plasma of the ne <∼ 5 × 1017 m-3 , and the correction of the finite current is necessary. A new relationship between Te and potential signals (Vf and Vp) where the finite current in the electrodes for Vf and Vp measurements is taken into account was derived, and experimentally confirmed the validity in the experiments of the Compact Helical System.

Keywords

triple Langmuir probe, load resistance, fluctuation measurement, floating potential, frequency response

DOI: 10.1585/pfr.2.S1091

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References

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This paper may be cited as follows:

M. TAKEUCHI, K. TOI, R. IKEDA, C. SUZUKI and CHS EXPERIMENTAL Group, Plasma Fusion Res. 2, S1091 (2007).