DEVELOPMENT OF CENTRIFUGAL SEPARATION METHOD OF ISOTOPES BY USE OF A J*B DRIVEN ROTATING PLASMA

该研究项目的目的是开发用于紧凑且经济的稳定同位素分离的血浆离心机。我们设计了两种类型的等离子体源：喷气旋转等离子体枪和真空放电旋转等离子体枪。他们成功地产生了气态旋转等离子体（Ar、He）和金属旋转等离子体（Zn/Cu、Cu、Mg/Al、Ag）。从实验和理论两方面研究了与旋转等离子体相关的重要问题，如加速特性、平衡和稳定性、带电粒子输运和离心分离系数。首先，建立了等离子体密度和速度与放电电流和磁场的比例关系。由于旋转速度与磁场有关且与放电电流成反比，因此建议使用超导磁体。接下来，观察等离子体表面不稳定性的开始及其向螺旋结构的演变。该机制被认为是由旋转等离子体和周围气体之间的速度剪切驱动的离心不稳定性。对于不同的气体和气压，我们测量了不稳定性增长速率、波幅、模数等。此外，我们还得到了初步结果，如果磁场足够强（>1T）足以磁化等离子体离子，那么不稳定性就会稳定。最后，我们进行了Zn/Cu混合旋转等离子体的离心质量分离实验。获得的最大分离因子为9，是传统气体离心机0.1的一百倍。

The aim of this research project is to develop plasma centrifuge for compact and economical stable-isotope separation. We designed two types of plasma sources : a gas-puff rotating plasma gun and a vacuum-discharge rotating plasma gun. They successfully generated gaseous rotating plasmas (Ar, He) and metal rotating plasmas (Zn/Cu, Cu, Mg/Al, Ag). Important problems associated with rotating plasmas such as the acceleration characteristics, the equilibrium and stability, charged-particle transport, and centrifugal separation coefficient have been investigated from both side of experiment and theory. First, the scaling relation of the plasma density and velocity against the discharge current and magnetic fields has been established. Because the rotational velocity is found to the magnetic field and inversely proportional to the discharge current, the use of superconducting magnet is recommended. Next, the onset of the instability on the plasma surface and its evolution to the spiral structure are observed. the mechanism is identified to be the centrifugal instability which is driven by the velocity shear between the rotating plasma and surrounding gas. For different gases and gas pressures, we measured the instability growth rate, the wave amplitude, the mode number, etc. In addition, we had a preliminaty result that the instability is stabilized if the magnetic field is strong (>1T) enough to magnetize plasma ions. Finally, we carried out the experiment on the centrifugal mass separation experiment for a mixed Zn/Cu rotating plasma. The maximum separation factor of 9 was obtained which was a hundred times as large as 0.1 of the conventional gas centrifuge.