Pellet Developments and Plasma Diagnostics

对等离子体输运的了解是实现聚变装置中高性能等离子体约束的关键。将杂质核注入聚甾烯胶囊会产生局部等离子体微扰，但也会出现一些额外的杂质，如胶囊中含有的碳。因此，建议使用由大量等离子体组分的冰制成的颗粒，即氢同位素作为胶囊。当这种小球进入等离子体时，外部的固体氢层首先被烧蚀，防止杂质核烧蚀到等离子体柱轴。这导致了核心的密集烧蚀，提供了沉积的示踪离子的少量局部化。实验观测到的杂质离子演化为分析计算大块等离子体的扩散系数提供了数据。因此，为了研究大型螺旋装置中的等离子体输运，研制了一种新型的在杂质核周围制备固体氢球的注入器。采用了一种新技术，将直径0.2 mm的碳芯或聚甾烯芯子从枪库自动装载到轻气炮身管中。该注入器配备了制冷机，能够在7~8K的温度下，在6分钟内形成长3.2 mm、直径3 mm、中心有杂质核的圆柱形固体氢球，并将其注入轻气炮，最大射速可达1 km/S。设计了一种带有导向管的差动泵送系统，用于将颗粒输送到等离子体并切断推进剂气体，并安装在喷射器和铲运机之间。

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.