Development of neutral particle control in steady-state high-temperature plasma

为了产生稳定的高温等离子体，必须开发一种新的粒子控制系统来降低外围区域的中性压力。为了研究膜泵在核聚变装置中的应用，我们研制了一台大型真空罐(600φ，1000L)膜试验装置。然后我们就可以进行各种膜抽运的实验。将该测试装置与原有的膜装置相结合，研究了膜表面杂质沉积对Nb膜透氢的影响，发现膜的透过率随杂质沉积的增加而降低。此外，还发现将膜加热到高温(~1200℃)时，沉积的杂质被分解到膜的主体中，膜的透过率可以恢复到原来的水平。在用电子回旋共振等离子体源SP-…研究室温下膜的性质时随着膜温度的降低，通过膜的氢气渗透量大大减少。结果发现，由于膜表面非金属杂质的存在，使得膜内外的势垒具有很大的不对称性是非常重要的。在最后一个财政年度，我们设计了一个Nb吸收板作为大型螺旋装置(LHD)的泵送系统，并使用安装到LHD中的原型吸收板进行了性能测试。在室温下，Nb板吸收了雾化器产生的氢原子，并且具有很强的吸氢能力(120Pam^3/S)，没有吸附的氢再释放。吸氢能力约为7×10~(-19)cm~(-2)S^~(-1)。此外，我们还通过实验得到了面板表面氢的复合系数，这使得我们能够更准确地评估作为泵浦系统的铌面板的性能。这一结果对今后核聚变装置面板泵的设计具有重要的指导意义。这块面板确实安装在LHD中，并证明了在等离子体实验中产生的氢原子的吸收。这是一个成功的结果，证明了Nb面板在实际聚变装置中的适用性。较少

For the purpose of producing a steady-state high-temperature plasma, a new particle control system must be developed for decreasing neutral pressure at the peripheral region. In order to make a research on the application of membrane pumping to nuclear fusion devices, we made a membrane test device with a large vacuum tank (600φ, 1000L). Then we could carry out various experiments on membrane pumping. By combining the test device with the previous membrane device, the effect of impurity deposition onto the membrane surface on hydrogen permeation through niobium membrane was investigated and it was found that the permeability decreased with increasing the impurity deposition. Moreover, it was also found that the deposited impurities were resolved into the bulk of membrane by heating the membrane up to the high temperature (〜1200℃) and the permeability could be recovered to the previous one. In the study of membrane properties at the room temperature by using an ECR plasma source, the sp … More eed of hydrogen permeation through the membrane extremely decreased with decreasing the membrane temperature. As a result, it was found that it was very important to make a large asymmetry of potential barrier due to nonmetal impurity on the membrane surface at the inside and outside of the membrane. In the final fiscal year, we designed a niobium absorption panel as the pumping system for the large helical device (LHD) and performed the performance test using a prototype absorption panel, which was installed into LHD. The niobium panel at the room temperature absorbed hydrogen atoms produced by an atomizer and the strong ability of hydrogen absorption (120 Pam^3/s) was demonstrated without the reemission of absorbed hydrogen. The capability of hydrogen absorption was about 7 x 10^19 cm^-2 s^-1. Moreover, we obtained the recombination coefficient of hydrogen on the panel surface experimentally and it enabled us to estimate the performance of niobium panel as a pumping system more exactly. This result is very useful for designing a panel pump for nuclear fusion devices in future. This panel was indeed installed into LHD and the absorption of hydrogen atoms produced during plasma experiment was demonstrated. It is a successful result to demonstrate the applicability of niobium panel to the real fusion device. Less