This study proposes a method for evaluating the axial decay length of the plasma pressure in detached helium plasmas with a fixed-point laser Thomson scattering and spectroscopic measurements in the linear divertor plasma simulator NAGDIS-II. By controlling the neutral gas pressure, the highly volume-recombining region called the “recombination front” was moved along the magnetic field. The differential terms for the electron pressure and the recombination-front position with respect to the neutral pressure were obtained. By using these two terms, the decay length of the plasma pressure was qualitatively calculated. In addition, from the movable Langmuir probe measurement, difference between the locally estimated decay length around the recombination front and the decay lengths over a wide axial range was discussed. The proposed method can be applied even in the huge heat flux condition where direct-contact measurements such as the Langmuir probe are not available.

这项研究提出了一种方法，用于在线性偏滤器等离子体模拟器NAGDIS-II中使用定点激光Thomson散射和光谱测量来评估分离的氦等离子体中的等离子体压力的轴向衰减长度。通过控制中性气体压力，被称为“复合前沿”的高体积复合区域沿着磁场移动。获得了电子压力和相对于中性压力的复合前位置的微分项。通过使用这两项，定性地计算出等离子体压力的衰减长度。此外，通过可移动的Langmuir探针测量，讨论了重组前沿周围的局部估计衰变长度与宽轴向范围内的衰变长度之间的差异。