Ultra-fast Langmuir probe measurements in MAST-U edge plasma

朗缪尔探针通常用于测量聚变和工艺等离子体中的等离子体参数，如电子温度、离子饱和电流和浮动电位。传统的朗缪尔探针系统，然而，不太适合等离子体湍流调查由于空间或时间分辨率的限制。实验表明，聚变等离子体的边缘区域是非常湍流的。例如，快速瞬态对流结构将等离子体粒子和热量径向向外传输穿过开放的磁场线（刮除层）。在探针头处安装有多个电极的中平面往复运动器是测量刮除层中细丝特性的关键诊断器。一种基于现场可编程门阵列（FPGA）的新型超快速朗缪尔探针系统目前正在由UKAEA、利物浦大学和麻省理工学院合作开发，预计将于2023年3月结束。预期这将使用单个电极提供所有三个等离子体参数的实时输出（~ 1 MHz时间分辨率）。这一拟议的主要是实验性的项目将继续发展这一系统，并将使用诊断来研究MAST-U球形托卡马克边缘等离子体区域的快速输运现象。

Langmuir probes are commonly used to measure plasma parameters such as electron temperature, ion saturation current and floating potential in fusion and technological plasmas. Conventional Langmuir probe systems, however, are not well suited for plasma turbulence investigations due to either a spatial or temporal resolution limitation. Experiments have shown that the edge region in a fusion plasma is very turbulent. For example, fast transient filamentary structures transport plasma particles and heat radially outward across the open magnetic field lines (scrape-off-layer). The midplane reciprocator, fitted with several electrodes at the probe head, is a key diagnostic for measuring filament properties in the scrape-off-layer.A novel ultra-fast Langmuir probe system, based on a field programmable gate array (FPGA), is currently being developed through a collaboration between UKAEA, University of Liverpool and MIT and is due to end in March 2023. This is expected to provide real-time outputs (-1 MHz temporal resolution) of all three plasma parameters using a single electrode. This proposed, primarily experimental, project will continue the development of this system and will use the diagnostic to investigate fast transport phenomena in the edge plasma region of the MAST-U spherical tokamak.