10月21日 Diagnostic development and transport in LHD

报告题目：Diagnostic development and transport in LHD

报告时间：10月21日（星期二）下午15:00

报告地点：EAST大厅3楼会议室

主持人：刘海庆 研究员

报告人简介：Toshiki Kinoshita, assistant professor in Kyushu university. Majors is diagnostic development and plasma confinement.

Achievements: Discovered the turbulence transition and background physics of the confinement isotope effect in LHD (IAEA-FEC2023 Poster Award, PRL2024). Achieved real-time turbulence control in LHD (IAEA-FEC2025 Oral Talk). 

报告简介：

In fusion research, it is essential to suppress anomalous transport through an understanding of turbulence characteristics in order to achieve high triple product. To this goal, the LHD has introduced a two-wavelength laser interferometer and two-dimensional phase contrast imaging (2D-PCI). The two-wavelength laser interferometer comprises a CO₂ laser and a quantum cascade laser. Using the quantum cascade laser as the second laser enables stable operation and reduces the vibrations in the CO₂ laser's phase by around 80%. Phase contrast imaging (PCI) is a technique used to measure line-integrated electron density fluctuations, and has been installed to many devices. Notably, the LHD uses the world's only two-dimensional detector to measure a radial profile of turbulence.

We addressed the following challenges using these diagnostics.

Improved confinement of deuterium plasma has been observed in both tokamak devices and the LHD. The improvement in confinement in tokamak devices can be explained by existing physics. However, the improvement in confinement in the LHD could not be explained by the same principles. Recently, precise turbulence measurements and simulations have led to the discovery of ITG-RI (resistive interchange mode) turbulence transitions. The negative dependence of this RI on ion mass makes it possible to explain the confinement improvement in deuterium plasma. Furthermore, last year's LHD experiments implemented turbulence control based on this transition to improve confinement. This resulted in suppressed turbulence and an improved H-factor. This presentation will detail these findings and also introduce progress on the development of instruments currently underway at QUEST.