Development of Measurement Methods of Electric Fields in Plasma Using Laser Spectroscopy

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There were three major limitations of electric field measurement methods in plasmas, which have prevented their use in practical discharges. These are, (1) species to be applied, (2) measurable lower detection limits of electric fields, and (3) measurable discharge pressures in collision-induced LIF. By the present study carried out in the fiscal years 1998-1999, there have been great progressives in overcoming each of these limitations as follows.1. The biggest achievement of the study is to have demonstrated the ability to deduce electric fields of any species, by comparing theoretically calenlated Stark profiles and experimental ones, in particular about the spectral appearances and their positions of optically forbidden lines under the presence of electric field.2. The main factors which decides the upper and lower limits of measurable electric fields have been discussed, and by choosing highly excited Rydberg levels, it has been shown that electric field measurements down to 1V/mm be possible.3. In order to overcome the pressure limitations, the scheme of two step laser induced fluorescence (TSLIF) was proposed, and its potential has been experimentally demonstrated.In addition, electric fields in sheath of discharge plasmas has been measuring using these established methods and its structure has been quantitatively discussed. Also, possibilities of applying these methods to high temperature plasma have been discussed.