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Development of new-type negative ion sources using powdery samples

利用粉状样品开发新型负离子源

基本信息

批准号：
08555077
负责人：
KAWANO Hiroyuki
金额：
$ 3.84万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

To develop new-type negative ion sources using powdery samples instead of gases or liquids, compact ion sources designed and manufactured by us were examined with many samples under various conditions. Namely, a small amount (-5 mg) of powder deposited directly on a fine mesh or a metal plate was bombarded by electrons (-100-300 eV, -1-3 mA/0.05 cm^2) emitled from a hot tungsten wire. By this method, such ions as D^-, Li^-, F^-, Na^-, Cl^-, Ag^- and O^- were successfully produced from those powdery samples of LiD, LiI, LiF, NaF, NaCl^-, AgCl and BaO, respectively. Especially, saline hydride (e.g., SrH_2) on a boat-type ribbon heated to -700-900 K was useful for producing H^- by both thermal and election-stimulated desorptions. In this case, electrons were supplied from the heated sample itself without using a special election gun. In other wards, the sample served as a triple source supplying H^-, e^- and SrH_2 (sublimated onto a surrounding slit plate). Both thermal desorption energy of H^- and work function of those active spots created by hydrogen release from the sample were determined by a stepwise or temperature-programmed heating method. The active spots consisting of alkali or alkali-earth metal were destroyed by admission of H_2 or O_2, but recreated by stopping the admission. Theoretical analysis of these results yielded a simple model explaining the mechanism of the thermal desarption. The currents of thee above ions after mass analysis were -10^<-12> - 10^<-9> A/0.05 cm^2 (apparent area of the emitting sample surface) and was constant in time to within *5% for more than -10h.In condusion, our compact ion sources (-2 cm^3) are usable for producing various negative ions with little release of gases during operation. Much further work, however, is needed to find the best powdery sample and experimental condition for producing a more stronger and stable beam for every ion species of interest.

为了开发新型负离子源，利用粉状样品代替气体或液体，我们设计和制造的紧凑型离子源在各种条件下用许多样品进行了测试。也就是说，少量（- 5mg）粉末直接沉积在细网或金属板上，由热钨丝发出的电子（-100-300 eV, -1-3 mA/0.05 cm^2）轰击。该方法成功地从LiD、LiI、LiF、NaF、NaCl^-、AgCl和BaO的粉末样品中分别制备出了D^-、Li^-、F^-、Na^-、Cl^-、Ag^-和O^-等离子。特别是，加热到-700-900 K的船形带上的盐水氢化物（如SrH_2）通过热和选举刺激解吸产生H^-是有用的。在这种情况下，电子从加热的样品本身提供，而不使用特殊的选择枪。在其他方面，样品作为三重源供应H^-， e^-和SrH_2（升华到周围的狭缝板上）。H^-的热解吸能和氢从样品中释放产生的活性点的功函数都是通过逐步加热或程序升温的方法来确定的。由碱金属或碱土金属组成的活性点在H_2或O_2进入后被破坏，但在停止进入后又被恢复。对这些结果的理论分析得出了一个简单的模型来解释热脱附的机理。质量分析后，上述三种离子的电流为-10^<-12> -10^<- 9> A/0.05 cm^2（发射样品表面的表观面积），并在-10h以上的时间内恒定在*5%以内。总之，我们的紧凑型离子源（-2 cm^3）可用于产生各种负离子，在操作过程中几乎没有气体释放。然而，需要进一步的工作来找到最佳的粉末样品和实验条件，以便为每个感兴趣的离子种类产生更强和更稳定的光束。