Development of Selective Hydrogen Pumping Method Using Lithium Films

人们希望开发一种新的泵送系统，其中氢同位素燃料(特别是氚)从氦灰中单独排出以重复使用。本研究旨在开发一种利用锂电池板进行选择性氢气抽运的独创技术。本文所取得的结果概括如下：1.在熔点(179ﾟC)以下，锂不与氢分子反应，而与氢原子和氢离子强烈反应生成氢化锂。这种吸氢是以每个锂原子一个氢原子的速率进行的，因此，由于氢在块状锂中的高速扩散，抽氢量与锂的表面积乘以锂层厚度成正比。在400ﾟC以上焙烧氢化锂，分解为氢分子和锂原子。这两个性质使我们能够构建一个氢气选择泵浦系统。也就是说，泵浦端口中弱电离氢放电或热丝诱导的氢解离导致锂电池板选择性吸氢。锂电池板在氢气饱和后，加热到400ﾟC会引起氢分子脱附，而氢分子会被常规泵耗尽，从而使锂电池板恢复到初始状态。应特别注意保持锂表面的清洁，因为它很容易与H_2O、O_2和CO等残余气体反应形成锂化合物。沉积锂薄膜的基材最好是金属，而不是与锂发生化学反应的石墨。

Development of a new pumping system where hydrogen isotope fuel (especially tritium) is separately exhausted from helium ash to reuse it has been desired. The present study is aimed at developing an original technique for selective hydrogen pumping with use of lithium panel. The results obtained here are summarized as follows.1. Below the melting point (179ﾟC), lithium does not react with hydrogen molecule but strongly does with hydrogen atom and hydrogen ion to form lithium hydride. This hydrogen absorption takes place at rate of single hydrogen atom per single lithium atom, so that the total amount of hydrogen pumping is proportional to a surface area times thickness of lithium layr, owing to high-speed hydrogen diffusion in bulk lithium.2. Baking of lithium hydride above 400ﾟC leads to decomposition into hydrogen molecule and lithium atom.3. These two properties listed above enable us to construct a hydrogen selective pumping system. Namely, weakly ionized hydrogen discharges or hot-filament induced hydrogen dissociation in pumping ports give rise to selective hydrogen uptake into lithium panel. After saturation of lithium panel with hydrogen, heating the panel up to 400ﾟC induces hydrogen molecule desorption which is exhaused by a conventional pump, recovering the lithium panel to the initial state.4. Special care should be payd to keep lithium surface clean since it easily react with such residual gases as H_2O,O_2 and CO,to form lithium compounds.5. Base materials where lithium films are deposited are preferably metal rather than graphite which chemically reacts with lithium.