The optical design of near-infrared phase contrast imaging (NI-PCI) diagnosis on HL-2A is introduced in this paper. This scheme benefits from the great progress of near-infrared laser technology and is a broadening of traditional phase contrast technology. This diagnostic can work as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations. Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed. The 1550 nm laser is chosen as the probe beam and high-precision optical components are designed to fit the laser beam, in which a phase plate with a 194-nm-deep silver groove is the key. Compared with the conventional 10.6 m laser-based PCI system on HL-2A, NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm⁻¹ to 32.6 cm⁻¹.

中文翻译：

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HL-2A 托卡马克新型近红外相衬成像 (NI-PCI) 诊断的光学设计

介绍了HL-2A近红外相衬成像(NI-PCI)诊断的光学设计。该方案受益于近红外激光技术的巨大进步，是传统相衬技术的拓宽。这种诊断可以作为一种敏锐的工具，通过推断弦积分等离子体密度波动来测量等离子体波数谱。详细设计了前光路（激光进入托卡马克等离子体之前的路径）和后光学系统（激光穿过等离子体之后的路径）。选择1550 nm激光器作为探测光束，并设计了适合激光束的高精度光学元件，其中带有194 nm深银槽的相位板是关键。与传统10.6相比 与HL-2A上基于激光的PCI系统相比，NI-PCI显着克服了不需要的相位闪烁效应，并提高了高波数湍流的测量能力，最大可测量波数从15 cm ^-1增加到32.6 cm ^-1。