Pellet Developments and Plasma Diagnostics

等离子体输运的知识是实现聚变装置中高性能等离子体约束的关键。将杂质芯注入聚苯乙烯胶囊中，会产生局部等离子体扰动，但胶囊中会出现一些额外的杂质，如碳。因此，建议使用由散装等离子体组分（即氢同位素）的冰制成的丸粒作为胶囊。当这样的弹丸进入等离子体，外部的固体氢层首先被烧蚀，保持杂质核心从烧蚀到等离子体柱轴。这导致芯的强烈烧蚀，从而提供沉积的示踪离子的小的局部化。实验观察到的杂质离子的演变提供了数据的解析计算的大块等离子体的扩散系数。因此，我们研制了一种新的注入器，用于在大螺旋装置中研究等离子体的输运。本文介绍了一种将直径为0.2 mm的碳或聚苯乙烯弹芯从轻气炮杂志自动装填到炮管中的新技术。该注入器装有低温制冷器，能在6分钟内在7-8 K温度下形成长3.2mm、直径3 mm的圆柱形固体氢芯块，芯块中心有一个杂质核，并能以1 km/s的速度注入轻气炮。喷射器中弹丸形成和加速的可靠性和技术是充分和有效的。已经设计了一个带有导管的差动泵送系统，用于将弹丸输送到等离子体并切断推进剂气体，该系统正在安装在喷射器和LHD之间。

Knowledge of plasma transport is a key for achieving high performance plasmas confinement in fusion devices. Injection of impurity cores inserted into polysterene capsules gives a local plasma perturbation, however, some extra impurities such as carbon contained in the capsule appear. Thus, it is proposed to use pellets made from ice of bulk plasmas components, i.e. hydrogen isotopes, as capsules. When such pellet enters the plasma, the outer solid hydrogen layer is ablated first, keeping the impurity core from ablation up to the plasma column axis. This results in an intensive ablation of the core providing the small localization of the deposited tracer ions. Experimentally observed evolution of the impurity ions gives data for analytical calculation of diffusion coefficient of the bulk plasmas. Thus, a new injector for making solid hydrogen pellets around impurity cores has been developed for plasma transport study in Large Helical Device. A new technique has been employed for automatic loading carbon or polysterene cores of 0.2 mm diameter from a gun magazine to a light-gas gun barrel. The injector is equipped with a cryorefrigerator and is able to form a 3.2 mm long and 3 mm diameter cylindrical solid hydrogen pellet at 7-8 K with an impurity core in its center within 6 minutes and to inject it in the light-gas gun up to 1 km/s. The reliability and technology of pellet formation and acceleration in the injector was sufficient and efficient. A differential pumping system with a guide tube for pellet transportation to the plasma and cutting off a propellant gas has been designed and is being installed between the injector and LHD.