The study of control of "partial" detached plasma and heat transport

偏滤器最有吸引力的特点是预期的能力，以创造一个密集和冷分离等离子体与低中性回流的主要等离子体。然而，等离子体压力的损失通常仅沿着几毫米宽的窄通量表面区域发生，并且通常仅发生在分界线附近。这种部分分离的等离子体产生于高温偏滤器区域和低温偏滤器区域之间的狭窄区域中。部分分离等离子体是一种非常复杂的现象，伴随着原子和分子的碰撞过程。利用热负荷、朗缪尔探针等常用的诊断方法难以控制分离和部分分离等离子体，在线性偏滤器等离子体模拟器TPD-SheetIV中，提出了一种基于负氢离子密度n_<H^->反馈控制的稳定分离等离子体的新方法。少量的二次吹气大大降低了靶板Q的热负荷，并迅速增加了等离子体外围的n_<H^->，而不增加辐射复合和三体复合。通过快速改变气体流量比G，使n_<H^->最大化，并保持气压P恒定，使分离的等离子体稳定地保持在靶板区域。新系统实现了降低分离等离子体中的Q和G量的目标。

The most attractive feature of the divertors has been the expected capability to create a dense and cold detached plasma with low neutral back flow to the main plasma. However, a loss of plasma pressure often only occurs along a narrow flux surface region of a few millimeters width and often occurs only near the separatrix. This partially detached plasma is produced in a narrow zone between the high and low temperature divertor regions. The partially detached plasma is a very complex phenomenon with atomic and molecular collision processes. It is difficult to control the detached and partially detached plasmas by commonly used diagnostics, such as heat loads, Langmuir probes, etc.We have developed a new way to stably maintain a detached plasma based on feedback control of the negative hydrogen ion density n_<H^-> in the linear divertor plasma simulator, TPD-SheetIV. A small amount of secondary gas puffing strongly reduced heat load of target plate Q and rapidly increased n_<H^-> in the periphery of the plasma without increased radiative and three-body recombination. The detached plasma is steadily maintained in the region of the target plate by rapidly varying gas flow ratio G so as to maximize the value of n_<H^-> and keep gas pressure P constant. The new system has achieved the goal of reducing both Q and amount of G in a detached plasma.