An investigation on the precision mounting process of large-aperture potassium dihydrogen phosphate converters based on the accurate prediction model

Abstract

Potassium dihydrogen phosphate(KDP) converters are important optics applied in the final optics assembly of inertial confinement fusion(ICF) facilities. The efficiency of the second harmonic generation is greatly affected by the phase matching error, which is induced by microsurface distortion. Firstly, considering the strict requirements of surface distortion and the associated measurement difficulties in the final optics assembly, an effective prediction model based on mechanical analysis is proposed to accurately predict the surface distortion of converters during mounting. Second, through the numerical simulation based on the prediction model, key factors that could have more influence on the surface distortion are analyzed. Then, measurements of the key factors are carried out to further improve the model. Mounting and surface measurement experiment are performed at an optical assembly building, and the results verify the accuracy of the prediction model. Third, because it is difficult to perform a field experiment for a KDP converter under tilted installation attitudes and during the mounting process, the prediction model is employed to analyze more factors that will influence the surface distortion in these conditions, and the analysis results provide helpful suggestions to optimize the mounting process. The results and findings in this article are meaningful for controlling mounting-induced surface distortion of KDP converters within the requirement of 3.2 μm. Moreover, the prediction model will solve the problem of online measurement in ICF facilities.