全超导托卡马克装置(EAST)充气成像系统光学设计

Design of GPI system on EAST

为了观测全超导托卡马克装置（EAST）中充气成像系统（gas puff imaging,GPI）的谱线强度,提出一套GPI光学观察系统。以匹兹伐型物镜为初始结构进行优化,使系统像差控制在1/4λ内,在观察波长656.2nm/587.6nm下,设计系统光学传递函数在16lp/mm下达到了0.76。对温度参数在20°-250°范围内作多重结构分析,选取的透镜材料热膨胀系数非常相近,光学频率在16lp/mm时,子午方向的光学传递函数几乎无变化,而弧氏方向的光学传递函数由0.82变化到了0.69。根据光学观察窗口所在物理环境,对其进行静力学、热力学仿真研究,可以看到石英窗口的形变量达到了1/5λ,将该形变代入光学设计中进行容差分析,系统的MTF≥0.5。通过快速相机捕捉到的系统成像光谱画面图显示,该系统能清晰地观察物面的谱线强度分布以及变化。

To observe the light spectrum of the gas puff imaging（GPI）on experimental advanced superconducting tokamak（EAST）,a GPI diagnostic optical window was designed.Based on the initial structure of the Petzwal lens,the optimization of the system was conducted.The aberration of the designed system was controlled within 1/4λ,and the modulation transfer function（MTF）was 0.76 at 16lp/mm with the wavelength of 656.2/587.6nm.Then the multi-configuration at the temperature of 20°-250°was analyzed,the lens material which had the similar coefficient of thermal expansion was selected,and the MTF at 16lp/mm was almost invariable in T direction,but it was changed from 0.82 to 0.69 in S direction,which was still in the design range.In addition,according to the physical environment of the optical window,the statics and the thermodynamic simulation was done to the window,the deformation of the window was 1/5λ,the tolerance analysis based on the value of the deformation showed that the optical system＇s MTF was still bigger than 0.5.Finally,the spectral images captured by rapid camera showed that the distribution and the change of the intensity could be clearly observed by the optical system.