A TEA CO
2 laser pumped FIR laser system for the collective scattering measurement of ion temperature has to be compact to be acceptable as a diagonostic tool. In order to develop a compact TEA CO
2 laser, a volumetric photo-preionization by v.u.v. radiation was systematically studied using two types of spark source, a free spark and a surface-gap spark. The photo-electron production was determined almost entirely by a partial pressure of CO
2. The surface spark was more efficient than the free spark, due to HL
αline enhanced by the evaporated epoxy resin. By using these results, the glow-arc region in TEA discharge is discussed.
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