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

高电流H^-/D^-离子源是制备中性束的必要条件，即中性束注入（NBI）加热聚变等离子体。为此，从实验、理论和计算（即粒子模拟）三方面研究了提高杂化型负离子源中H^-/D^-产生和提取的基本过程。研究结果如下：1。证实了D^-离子与H^-离子一样是由所谓的两步法产生的。也就是说，D^-离子是由慢等离子体电子与高振动激发分子的解离附着产生的，而这些分子是由快电子的碰撞激发产生的。使用双等离子体法（即控制好快电子的能量分布），可以清楚地观察到由于快电子的增加而引起的H^-/D^-产生的增强。随着放电条件的改变，在某些等离子体参数下，D^-离子明显高于H^-离子。根据负离子模型的数值模拟，在有和没有铯效应的情况下，等离子体参数对H^-/D^-产生的依赖性都得到了很好的再现。利用静电粒子模拟代码（二维空间和三维速度空间），研究了电子在磁滤波器上的传递和电势的形成，以及从源中提取负离子。发现电子的无碰撞异常扩散在确定主等离子体电位高于扩散等离子体电位的势结构中起着重要作用。

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.