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Description
Abstract: ECEI (Electron Cyclotron Emission Imaging) has been widely used in multiple nuclear fusion experimental devices and is one of the most important diagnostic systems on the HL-3 Tokamak for measuring the two-dimensional electron temperature perturbations. The optical system, as a key component of the ECEI diagnostic, determines the spatial resolution, field of view, and signal-to-noise ratio of the temperature perturbation images. In this paper, the laboratory test and calibration of the ECEI optical system on the HL-3 Tokamak will be reported, including the local oscillator (LO) coupled optics and the radio frequency (RF) receiving optics, to ensure good operation during the experimental campaign. The LO lens, focal lens and zoom adjust lens can be remotely controlled by stepping motors independently. Additionally, the imaging performance of the optical devices was further verified through advanced numerical simulations. The LO optics successfully drove the antenna array and the mixer diodes, and the beam intensity of the upper/lower antennas detecting the plasma edge was more than 36% relative to the center antenna detecting the plasma core. The focal region of the RF optics covered the entire region of interest without harmonic overlap and could work in narrow, medium, and wide zoom modes to meet different physical requirements, such as macro-scale MHD or micro-scale turbulence studies. The poloidal spatial resolutions in narrow, medium, and wide zoom modes are 3cm,3.5cm and 3.8cm, respectively. In the wide zoom mode, almost all image surfaces were very flat with a maximum offset of about 5cm, which matched well with the electron cyclotron emission layer in the plasma and ultimately resulted in good localization and spatial resolution of the ECEI measurements. Preliminary data of ECEI measurement have been obtained in the 2024 HL-3 experimental campaign and the behaviors of MHD, such as tearing mode etc., will be presented.
This work was supported by Innovation Program of Southwestern Institute of Physics （Grants No. 202301XWCX001-02) and Sichuan Science and Technology Program (Grant No. 2023ZYD0014）
