Development of vertical edge Thomson scattering diagnostic on HL-2M Tokamak

• Published in: Fusion engineering and design Vol. 193; p. 113846
• Main Authors: Gong, S.B., Zhang, T.C., Guo, W.P., Hou, Z.P., Zhai, W.Y., Liu, C.H., Deng, B.H., Shi, Z.B., Yu, L.M., Chen, W., Zhong, W.L., Xu, M., Duan, X.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2023
• Subjects: Electron density; Electron temperature; HL-2M; Thomson scattering; Electron temperature; Electron density; Thomson scattering; HL-2M
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2023.113846

•Analyzing the propagation characteristics of non-Gaussian beam.•Designing an in-vacuum collection optics with stable safety shutter structure.•Developing a new compact polychromator suitable for multi-point measurements. A vertical edge Thomson scattering diagnostic system on HL-2 M Tokamak has been developed recently. A Nd: YAG laser (1064 nm, 0.6–2.0 J, 30 Hz, 15 ns) is used as the probe beam. The laser beam propagates vertically through the plasma region and the scattered light is observed horizontally. The combination of a half-wave plate and a polarized beam splitter is used for stray light suppression. A group of in-vacuum collection lens is designed to image the 400 mm scattered region onto the rectangular fiber arrays. The laser beam waist and vertical spatial resolution are 2 mm and 10 mm, respectively. Scattered light is imaged on the 2.20 × 2.86 mm (10 × 13) fiber optic bundle. The development of collection optics with a special designed safety shutter ensures a reliable scattered signal, where the solid angle at central field of view (FOV) is 0.018 sr. A compact polychromator is developed to measure the scattered light. Relative calibration of the filter response (1060 nm, 1052 nm, 1029 nm and 982 nm) and absolute calibration by nitrogen Raman scattering have been completed. In the 2022 plasma campaign of HL-2M, the scattering signal is measured at E0 = 1.2 J, confirming the capability of the system for pedestal measurement in the future H-mode campaign.