プラズマ中の電界のレーザー分光法による新しい計測法の開発

概要

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The technique reviewed in this article can be traced back to the work first demonstrated in 1984 in which an electric field in a glow discharge plasma was measured using laser optogalvanic(LOG)spectroscopy against the Stark splitting of Rydberg levels of helium atoms. Subsequently, the technique of laser-induced fluorescence(LIF)was shown to be possible for this scheme in 1993, and electric fields of more than a few tens of V/mm in helium and argon for pressures above a few hundreds of mTorr have been measured and sheath structures in DC and RF discharges have been studied. Because these limitations have been very restrictive, it has so far failed to become a standard and general technique of electric field measurements in plasmas. However, during the last couple of years, new proposals have been made in which the technique has been extended by using two tunable lasers. This technique looks very promising in providing one of the "dreams" in plasma diagnostics, namely the measurement of electric field of "the order of or less than 1V/mm". In this article, the developments of the above laser spectroscopy are first reviewed and the main results of the discharge studies are summarized. New proposals are then described, together with results of computer simulations of LIF signals and the first experimental observation.
1999-03-25