Pellet Developments and Plasma Diagnostics

了解等离子体输运是在聚变装置中实现高性能等离子体约束的关键。将杂质芯注入聚甾体胶囊中会引起局部等离子体扰动，但会出现一些额外的杂质，如胶囊中所含的碳。因此，建议使用由大块等离子体成分（即氢同位素）制成的冰丸作为胶囊。当这种颗粒进入等离子体时，外层的固体氢层首先被烧蚀，使杂质核心不被烧蚀到等离子体柱轴。这导致了核心的强烈烧蚀，提供了沉积的示踪离子的小定位。实验观察了杂质离子的演化过程，为体等离子体扩散系数的分析计算提供了数据。因此，开发了一种新的围绕杂质芯制备固体氢球的进样器，用于大型螺旋装置等离子体输运研究。采用了一种新技术，将直径为0.2 mm的碳芯或聚脂芯从枪弹匣自动装入轻气枪管。该喷射器配有冷冻机，能够在7-8 K温度下，在6分钟内形成长3.2 mm、直径3mm的圆柱形固体氢球，其中心有杂质芯，并将其注入到速度为1 km/s的光气枪中。进样器造球和加速的可靠性和技术是充分和有效的。在喷射器和LHD之间设计并安装了一个带有导管的差动泵系统，用于将颗粒输送到等离子体并切断推进剂气体。

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.