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Studies on the mechanism of negative ion production in the magnetic multipole ion source

磁性多极离子源负离子产生机理研究

基本信息

批准号：
13680568
负责人：
MIYAMOTO Seiji
金额：
$ 2.05万
依托单位：
OSAKA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13680568/
关键词：
magnetic multipole ion source negative ion NBI electron enerrv distribution function magnetic filter arc discharge tantalum filament argon gas mixin フィラメント材体積生成カスプ磁場放電電子の閉じ込め静電バイアス

项目摘要

As the required energy for neutral beam being high due to the enlargement of thermonuclear fusion experimental devices, there have arisen the needs of negative-ion-based neutral beam injector (NEI). The object of this research is to find optimum conditions for negative ion production by controlling spatial distribution of electron temperature.It was indispensable to prevent discharge electron from penetrating into extraction region for negative ion production. Magnetic filters were usually introduced for this purpose, but there was a fault that the filters reducedplasma density inevitably. In this experiment, it was aimed at to trap discharge electron in the wall magnetic field without any magnetic filters introduced, adjusting the position of the filaments in a source. As the result, it wasattained to decrease electron temperature without reducing density in the extraction region.High-energy discharged electron was eliminated by magnetic filter, but there still remained the possibility that electron temperature was not optimized for negative ion production. We therefore introduce a new type of magnetic Biter which consisted of a watercooled coil. It was found that negative ion production was sensibly affected by electron temperature in the absence of discharge electron.Material of filaments was also considered to affect the negative ion production. Tantalum filament was tested and the negative ion current was increased in few ten percent in low gas pressures. As well as changing filament material, mixing argon into hydrogen gas was tested and the effect was investigated.Accomplishing these experiments, we developed a method to measure electron energy distribution function by a Langmuir probe and observed a high energy tail in the distribution function. The method is useful to measure and analyze discharge electron motion, which had to be inferred from computer simulation till now.

随着热核聚变实验装置的大型化，对中性束流能量的要求越来越高，对基于负离子的中性束注入器（NEI）的需求日益迫切。本研究的目的是通过控制电子温度的空间分布来寻找负离子产生的最佳条件，防止放电电子穿透到负离子产生的引出区是必不可少的。磁过滤器通常用于此目的，但存在一个缺点，即过滤器不可避免地降低了等离子体密度。在实验中，不引入任何磁过滤器，通过调整灯丝在源中的位置，将放电电子捕获在壁磁场中。结果表明，在不降低引出区密度的情况下，实现了电子温度的降低，磁过滤器消除了高能放电电子，但仍存在电子温度不适合负离子产生的可能性。因此，我们介绍了一种新型的磁咬，它包括一个水冷线圈。结果表明，在无放电电子的情况下，电子温度对负离子的产生有明显的影响，灯丝的材料也对负离子的产生有影响。对钽丝进行了测试，在低气压下负离子电流增加了百分之十几。在改变灯丝材料的同时，还进行了氩气与氢气混合的实验研究，并在实验的基础上，发展了一种用朗缪尔探针测量电子能量分布函数的方法，观察到了分布函数中的高能拖尾现象。该方法对于测量和分析放电电子运动具有一定的实用价值，而目前放电电子运动的测量和分析只能通过计算机模拟来实现。