Kim Dong-Kwon, Lee Jaehyun, Lee Dong Jae, Yun Gunsu S
Department of Physics, POSTECH, Pohang, Gyeongbuk 37673, Korea.
Korea Institute of Fusion Energy, Daejeon 34133, Korea.
Rev Sci Instrum. 2024 Aug 1;95(8). doi: 10.1063/5.0219245.
The two electron cyclotron emission imaging (ECEI) systems installed at adjacent ports (G and H) on the KSTAR tokamak incorporate large-aperture mm-wave optics, broadband electronics, and high speed digitization (up to 1 MSa/s) for 2D and quasi-3D visualization of MHD-scale fluid dynamics. Recently, the ECEI systems have been proved to be capable of visualization of smaller scale fluctuations albeit with a limited spatiotemporal resolution and even capable of measurement of ion cyclotron harmonic waves by direct high-speed sampling of the ECE IF signals. A four-channel prototype subsystem with a higher sampling rate up to 16 GS/s has been integrated into the G-port ECEI system, enabling the measurement of plasma waves in the GHz range in the form of modulated ECE signals and characterization of high-frequency turbulence during the evolution of pedestal. To achieve higher toroidal resolution in the turbulence measurement, the H-port ECEI system is now being upgraded to have a toroidally dual detector array of 2(toroidal) × 12(vertical) × 8(radial) channel configuration and a high-speed subsystem of 2(toroidal) × 4 channel configuration. The new mm-wave optics has been designed via beam propagation simulation, and the measured performance of the fabricated lens indicates a toroidal resolution of 8-10 cm depending on the focus position and zoom factor, allowing for the measurement of parallel wavenumber up to k‖ ∼ 0.8 cm-1.
安装在韩国超导托卡马克先进研究装置（KSTAR）托卡马克相邻端口（G和H）的两个电子回旋辐射成像（ECEI）系统，集成了大孔径毫米波光学器件、宽带电子设备和高速数字化技术（高达1 MSa/s），用于对磁流体动力学（MHD）尺度的流体动力学进行二维和准三维可视化。最近，ECEI系统已被证明能够可视化较小尺度的波动，尽管时空分辨率有限，甚至能够通过对ECE中频信号进行直接高速采样来测量离子回旋谐波。一个采样率高达16 GS/s的四通道原型子系统已集成到G端口ECEI系统中，能够以调制ECE信号的形式测量GHz范围内的等离子体波，并在基座演化过程中对高频湍流进行表征。为了在湍流测量中实现更高的环向分辨率，H端口ECEI系统目前正在升级，以拥有一个2（环向）×12（垂直）×8（径向）通道配置的环向双探测器阵列和一个2（环向）×4通道配置的高速子系统。新的毫米波光学器件已通过光束传播模拟进行设计，所制造透镜的测量性能表明，根据聚焦位置和变焦系数，环向分辨率为8-10厘米，能够测量高达k‖ ∼ 0.8厘米-1的平行波数。
