Development of Selective Hydrogen Pumping Method Using Lithium Films

人们希望开发一种新的泵送系统，将氢同位素燃料（尤其是氚）从氦灰中分离出来，重新利用。本研究旨在开发一种利用锂板选择性抽氢的原创技术。本文的研究结果总结如下：在熔点（179 C）以下，锂不与氢分子反应，但与氢原子和氢离子反应强烈，形成氢化锂。这种吸氢的速率是每单个锂原子一个氢原子，因此抽氢总量与锂层的表面积乘以锂层厚度成正比，这是由于氢在大块锂中的高速扩散。氢化锂在400℃以上烘烤，分解为氢分子和锂原子。上面列出的这两个特性使我们能够构建一个氢选择性泵送系统。也就是说，弱电离的氢放电或热丝诱导的氢解离在抽气口产生选择性的氢吸收到锂板中。3 .锂板充氢饱和后，加热至400ºC，诱导氢分子解吸，用常规泵将氢分子排出，使锂板恢复到初始状态。4 .锂表面易与H_2O、O_2、CO等残余气体反应生成锂化合物，应特别注意保持锂表面清洁。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.