HT-7 Nd:YAG激光汤姆逊散射光学系统分析

 光学透过性能对信号微弱的激光汤姆逊散射测量系统极为重要。主要讨论了HT-7 Nd:YAG激光汤姆逊散射系统光学设计中消除杂散光和提高散射信号传输效率的方法，并对系统的光学性能进行了模拟计算。模拟结果显示，干涉滤光片分光谱仪的光学透过性能随电子温度的升高而增强，等离子体电子温度为1 keV时其透过率可达到10%；汤姆逊散射信号非常微弱，等离子体电子密度为1×10¹⁹/m³时每道信号仅有几百到上千个光子；等离子体电子温度在0.3～5.0 keV范围内时，光子量子统计涨落引起的电子温度测量误差在3%以下。

Optical system of the Nd:YAG laser Thomson scattering device on HT-7 Tokamak

Optical transmission is a key issue of the Thomson scattering system due to the weak scattered signal. In this paper, the methods of reducing the stray light and increasing the optical transmittance of the system is discussed. Simulation shows that the transmission of the polychromator is nearly proportional to the electron temperature and it reaches 10% when electron temperature is 1 keV. Scattered signal is very small and there are only hundreds of photons in each channel when electron density is 1×1019/m3. When the electron temperature is more than 300 eV, the measuring uncertainty of the system from photon fluctuation is less than 3%.