The injection of energetic neutral atoms is a major component of plasma heating in fusion experiments. In order to fulfill the requirements of the ITER neutral beam injection (NBI), a RF-driven ion source for negative ions has been developed at the MPI für Plasma Physik (IPP Garching). Negative hydrogen ions are generated on a converter surface by impinging neutral particles and positive ions under the influence of magnetic fields and the plasma sheath potential. A 3D negative ion trajectory calculation including a Monte Carlo description of reactions and collisions with plasma particles was used to calculate the total and spatially resolved extraction probabilities for realistic field topologies and geometries of the large scale extraction system LAG. The experimentally observed increase in extracted ion current by the use of chamfered aperture collars agrees with the results of the ion transport simulation. Profiles of the extraction probability on the converter show that most of the extracted negative ions are created in the vicinity of the plasma grid apertures. These areas of intensified extraction probability are influenced by the magnetic field configuration. The ion extraction probability is affected by the long ranging magnetic filter field. The short ranging electron deflection field, however, which is generated by magnets near the converter surface, does not significantly influence the extraction probability.
高能中性原子注入是聚变实验中等离子体加热的主要组成部分。为了满足ITER中性束注入（NBI）的要求，马克斯·普朗克等离子体物理研究所（IPP Garching）开发了一种射频驱动的负离子源。负氢离子在转换器表面通过中性粒子和正离子在磁场和等离子体鞘层电势的影响下轰击而产生。利用包含蒙特卡洛描述的反应和粒子碰撞的三维负离子轨迹计算，对大型提取系统LAG在真实场拓扑和几何结构下的总提取概率和空间分辨提取概率进行了模拟。实验观察到的通过使用斜切孔径收集极使提取离子流增加的现象，与离子输运模拟结果一致。转换器上的提取概率分布表明，大部分提取的负离子产生于等离子体栅极孔径附近。这些提取概率增强的区域受到磁场构型的影响。长程磁场对离子提取概率有影响；然而，由靠近转换器表面的磁体产生的短程电子偏转磁场对提取概率没有显著影响。