金属氘化物电极真空弧放电等离子体输运过程中的轻重离子分离机制研究

Metal deuteride electrode vacuum arc ion source is one of the core components of the neutron generator. Improving the ratio of deuterium to metal ions, can improve the overall performance of neutron generators. In recent years, it has been found that the light and heavy ions in the vacuum arc discharge plasma have a tendency to be separated in space. By using this separation trend, the deuterium ion ratio can be effectively improved. The study of the separation mechanism is focused on the cathode spot region during the plasma transport process, and there are few studies on the possible mechanisms in the jet region. Therefore, this project will focus on the plasma of the jet region, using numerical simulation and experimental methods to carry out research to explore the physical mechanism of light and heavy ion separation. Firstly, the particle transport model will be established by using the method of particle simulation. The mechanisms of self-consistent electric field and particle elastic collision for the separation of light and heavy ions will be investigated. Then, the spatial distribution of the ions in the plasma of the jet region will be obtained by ICCD camera imaging method and magnetic analysis method. To clarify the separation mechanism，experimental results and model results will be checked. Finally, a new structure will be proposed to improve the deuterium ion ratio in the source plasma. The research of this topic is of great significance to understand the internal physical mechanism of ion source and the development of high performance neutron generator.

金属氘化物电极真空弧离子源作为中子发生器的核心部件之一，提高其等离子体中氘离子对金属离子的比例，可改善中子发生器的整体性能。近年实验发现真空弧放电等离子体中的轻重离子在空间上具有分离的趋势，利用这种分离趋势，可有效提高氘离子比。针对该分离机制的研究目前集中于等离子体输运过程中的阴极斑区域，而对射流区域中可能存在的机制研究较少。因此，本项目将针对射流区域的等离子体，采用数值模拟与实验相结合的方法开展研究，探索其中轻重离子分离的物理机制。首先采用粒子模拟的方法，建立射流区等离子体的输运模型，考察自洽电场及粒子弹性碰撞两种机制对轻重离子分离的影响；然后采用ICCD相机成像法及磁分析法获得射流区等离子体中各离子的空间分布，与模型结果校核，进一步明确分离机制；最后设计了一种提升源等离子体中氘离子比的新结构。本课题的研究对于了解离子源内部物理机制及研制高性能中子发生器，具有重要意义。

脉冲中子管在石油探井、爆炸物检测等领域具有广泛的应用，它的关键部件之一是含氘电极真空弧离子源。该离子源同时产生氘离子和金属离子。为了获得高产额，一般要求离子源氘离子比例越高越好。真空弧放电时存在轻重离子分离现象，利用此规律有望获得高氘离子比例的离子源。本项目对真空弧放电时存在的轻重离子分离现象进行了详细的研究，利用PIC算法模拟了不同结构下等离子体膨胀过程，发现轻重离子分离来源于离子轴向喷射和径向扩散速度的差异；利用ICCD相机拍摄了不同离子的空间分布，验证了轻重离子在径向上的分离机制；利用升级后的简易磁分析装置测量了径向上氘离子比例，也符合轻重离子分离机制预期。最后，利用轻重离子分离机制，设计了迷宫式等离子体膨胀路径，获得了氘离子比例80%以上的离子源结构。本项目研究成果不仅可以加深对真空弧放电的物理认识，还可以促进国内脉冲中子管技术的进步，缩小和国外产品之间的差距。