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

铯对增强混合型负离子源负离子产生和负离子提取的作用

基本信息

批准号：
06452424
负责人：
FUKUMASA Osamu
金额：
$ 4.1万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

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.

聚变反应中中性束的制备需要强流H^-/D^-离子源，即聚变等离子体的中性束注入（NBI）加热。为此，我们从实验、理论和计算（即粒子模拟）等方面研究了混合型负离子源中H^-/D^-产生和提取的基本过程。结果表明：1. D^-离子的产生与H^-离子的产生一样，也是通过所谓的两步过程进行的。也就是说，D^-离子是由慢等离子体电子与高振动激发的分子解离产生的，而这些分子是由快电子碰撞激发产生的（即，快速电子的能量分布被很好地控制），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。4.根据负离子模型的数值模拟，对于有和没有铯效应的情况，5.利用静电粒子模拟程序，对H^-/D^-产生的等离子体参数依赖性进行了模拟（空间二维，速度三维）、电子输运和磁过滤器上的电势形成，以及负离子的引出。结果表明，电子的无碰撞反常扩散在决定主等离子体电势高于扩散等离子体电势的电势结构中起着重要作用。