Basic study on the development of "superpermeable" membrane for pumping and refinement of plasma exhaust

研制了一套模拟聚变装置等离子体排气的实验装置，并分别安装了离子源、原子源和等离子体源，研究了“超渗透”膜的渗透行为。采用原子束源研究了原子驱动氘在铌中的渗透行为。由于AES（俄歇电子能谱）的“原位”表面分析显示，上游侧表面被硫覆盖，发现硫即使在原子暴露下也非常稳定。渗透行为被认为是在这种表面状态的影响下，其中渗透概率被发现在600和900 K之间的温度范围内几乎是恒定的。这种依赖性反映了“超渗透”的一个特征，并且从本研究中可以预期，“超渗透”可以通过仔细处理表面条件来控制。从俄罗斯购买了安装有碳靶的等离子体源，并将其与渗透试验台结合，以研究等离子体驱动的“超渗透”膜（Nb）的渗透行为。该装置被构造成等离子体的点火轰击碳靶以在膜表面上沉积存款碳杂质层。在初步实验中，当等离子体放电被点燃时，在暴露于原子氢的情况下最初实现了稳态渗透速率。这清楚地表明，由于碳沉积，渗透速率降低。

Experimental devices installed with ion, atom as well as plasma sources are developed to simulate the plasma exhaust in fusion device, and the permeation behavior of "superpermeable" membrane was investigated. An atomic beam source was employed to study the atom-driven permeation behavior of deuterium through Nb. "In-situ" surface analyses due to AES (Auger Electron Spectroscopy) revealed that the upstream-side surface was covered with sulfur, which was found to be very stable even under the atomic exposure. The permeation behavior was considered to be under the influence of this surface state, where the permeation probability was found to be nearly constant in the temperature range between 600 and 900 K. Such a dependence reflects one feature of "superpermeation" and it is expected from the present study that "superpermeation" can be controlled through careful treatment of the surface conditions. An plasma source installed with a carbon target was purchased from Russia and was incorporated with a permeation test stand to investigate the plasma-driven permeation behavior of "superpermeable" membrane (Nb). The device is so constructed that ignition of plasma bombards the carbon target to deposit carbon impurity layer on the membrane surface. In the preliminary experiment, a steady-state permeation rate was achieved initially under exposure to atomic hydrogen, when the plasma discharge was ignited. It was clearly shown that the permeation rate decreased as a result of carbon deposition.