Cesium Effects on Enhancing Negative Ion Production in and Negative Ion Extraction from the Hybrid Type Negative Ion Sources

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High Current H^-/D^- ion sources are required for the preparation of neutral beams in the fusion community, i.e.Neutral Beam Injection (NBI) heating of fusion plasmas. To this end, basic processes for enhancementof H^-/D^- production in and extraction from the hybrid type negative ion sources, have been studied, experimentally, theoreticelly and computationally (i.e.particle simulation). Findings are as follows :1.It is confirmed that D^- ions are produced by the so-called two step process as for H^- production. Namely, D^- ions are generated by dissociative attachment of slow plasma electrons to highly vibrationally excited molecules, and these molecules are produced by collisional excitation of fast electrons.2.With the use of double plasma method (namely, the energy distribution of fast electrons are well controlled), enhancement of H^-/D^- production caused by increasing fast electrons is clearly observed.3.With the change of discharge conditions, D^- ions are apparently higher than H^- ions under some plasma parameters.4.According to the numerical simulation of the negative ion model, for both cases with and without cesium effects, plasma parameter dependences of H^-/D^- production are well reproduced.5.With the use of the electrostatic particle simulation code (two-dimensional in space and three-dimensional in velocity space), electron transport and the potential formation across the magnetic filter, and the extraction of negative ions from the source are studied. It is found that the collisionless anomalous diffusion of electrons plays an important role in the determining the potential structure where the potential of the main plasma is higher than that of the diffused plasma.