Research and Development of a High Current Deuterium Negative Ion Source

高电流氢/氘负离子源是核聚变界对中性束制备的兴趣所在，即核聚变等离子体的NBI加热。为此，在实验、理论和计算（即粒子模拟）上研究了提高体积源中H^-产生和H^-提取的基本过程。(1)从理论上很好地阐明了快电子e_f在H^-生成过程中的作用。振动分子H_2^*，对于H^-的产生是必不可少的。在H_2^*的几种生产工艺中，e_f对H_2^*的碰撞激发是提高H^-产率最重要的。(2)实验明确了等离子体栅极优化的H^-离子提取与桶源等离子体参数之间的关系。(3)新设计了双等离子体型负离子源。在该源中，通过改变两个等离子体之间的电位差可以很好地控制e_f的能量分布和数量。由所谓的两步过程引起的氢离子的批量生产在实验上得到了很好的证实。(4)采用二维静电粒子模拟的方法研究了磁滤波器中能量依赖的电子输运，以及H^-离子的提取。(5)氘等离子体生成良好，提取出体积生成的D^-离子。同位素效应目前正在研究中。

High current hydrogen/deuterium negative ion sources are of interest to the fusion community for the preparation of neutral beams, namely NBI heating of fusion plasmas. To this end, basic processes for enhancement of H^- production and H^- extraction in volume sources have been studied experimentally, theoretically and computationally (i. e. particle simulation).(1) The role of fast electrons e_f in H^- production processes is well clarified theoretically. Vibrational molecules H_2^*, are essential to H^- production. Among some production processes of H_2^*, the collisional excitation of H_2^* by e_f is most important to enhance the H^- yield.(2) Relationship between extraction of H^- ions optimized by plasma grid potential and plasma parameters in a bucket source is clarified experimentally.(3) A double plasma type negative ion source is newly designed. In this source, the energy distribution of e_f and its quantity are well controlled by changing the potential difference between two plasmas. Volume production of H^- ions caused by the so-called two step process is well confirmed experimentally.(4) Two dimensional electrostatic particle simulation is implemented to study energy dependent electron transport across a magnetic filter, and to study extraction of H^- ions.(5) Deuterium plasmas are well produced, and volume produced D^- ions are extracted. Isotope effects are now under study.