Study of Plasma Neutralizer Cell for Negative Ion Beam

在基于负离子的中性光束注入（NBI）系统的设计中，从离子到中性光束的中性化效率可以通过利用等离子体中性化器来提高。在气体中性化器的情况下，转换效率为59%的最大值。在等离子体中性化器的情况下，70%的效率可以实现，因为在任何负离子中，减少了双重断裂反应，从而将负离子转化为正离子。这需要使用较高的离子化率（10%>）来获得较高的离子化率，这对在压力较低的情况下使用良好的容器来生产等离子体是很重要的。为了达到这个目的，我们制造了一个直径为310毫米的圆柱形释放器，直径为1400毫米的立方体磁场。通过薄膜研究使用氢、argon和Xenon作为用电弧放电的工作气体的放电特性和等离子体共振特性。It is found that in the case of gas pressure higher than 0.2 Pa， the plasma density was higher than n>10イイD111イエD1-3イエD1， but the ionization ratio was smaller than 1%。然而，在0.2 Pa以下的气体压力的情况下，电离比率迅速地随着压力的减少而减少。这是多么困难，以至于在气体压力低于0.1 Pa的情况下保持稳定的等离子体放电，这表明容器确定最低气体压力和最高电离的确认属性的等离子体有效性。在这项研究中，0.03帕的压力较低，氢的电离率为1.3%，argon为3.2%，Xenon为8%。这也是发现的，因为等离子体密度和电离率可以更高，以提高共识。我们从等离子体中性化器中获得了足够的密度和超过10%的电离率的前景。

In the design of negative-ion based neutral beam injection (NBI) system, neutralization efficiency from ion to neutral beam can be improved by utilizing plasma neutralizer. In the case of gas neutralizer, the conversion efficiency is 59% maximum. In the case of plasma neutralizer, efficiency of 70% can be achieved, because of reduced double stripping reaction in which a negative ion is converted to a positive ion. This requires the plasma with as high ionization ratio as possible (10%>).To get high ionization ratio, it is important to produce plasma at low pressure with using a container of good confinement. For that purpose, we made a cylindrical discharge with vessel of the size of 310mm in diam and 1400mm in length with cusp magnetic field. Discharge characteristics and plasma confinement properties were studied using hydrogen, argon and xenon as working gas with arc discharges by filaments. It is found that in the case of gas pressure higher than 0.2 Pa, the plasma density was higher than n>10ィイD111ィエD1 cmィイD1-3ィエD1, but the ionization ratio was smaller than 1%. But, in the case of the gas pressure under 0.2 Pa, the ionization ratio increased rapidly as the pressure decreased. It is however difficult to keep the stable plasma discharge at the gas pressure less than 0.1 Pa, hence the plasma efficiency of the confinement properties of the vessel determines minimum gas pressure and the highest ionization. In this study, the pressure of 0.03 Pa was the lowest and the ionization ratio of 1.3% for hydrogen, 3.2% for argon and 8% for xenon were achieved. It was also found that the plasma density and ionization ratio could be higher with improving the confinement. We obtained prospect of the plasma neutralizer which would have an enough density and the ionization ratio of more than 10%.