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

为了产生稳态高温等离子体，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，我们研制了一种大型真空罐（600φ, 1000L）的膜试验装置。然后我们可以进行膜泵的各种实验。将该测试装置与之前的膜装置相结合，研究了膜表面杂质沉积对氢通过铌膜的影响，发现随着杂质沉积的增加，渗透率降低。同时发现，将膜加热至高温（~ 1200℃）后，沉积的杂质被分解到膜体中，渗透率可恢复到原来的水平。用ECR等离子体源对室温下的膜性能进行了研究，发现随着膜温度的降低，氢通过膜的速率大大降低。结果发现，在膜的内外表面由于非金属杂质而产生较大的势垒不对称是非常重要的。在最后一个财政年度，我们设计了一个铌吸收板作为大型螺旋装置（LHD）的泵送系统，并使用安装在LHD中的原型吸收板进行了性能测试。铌板在室温下吸收由雾化器产生的氢原子，具有较强的吸氢能力（120 Pam^3/s），且不会再释放吸收的氢。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铌板表面氢气的复合系数，使我们能够更准确地估计铌板作为泵送系统的性能。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。该面板确实安装在LHD中，并演示了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，证明了铌板在实际聚变装置中的适用性。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