Optimization Of Back Support Structure Of Mirror Based On Response Surface Methodology

In recent years,considerable progress has been made in the research of inertial confinement fusion(ICF)devices with nuclear explosion simulation background,scientific research value and commercial prospects.The driving energy of ICF device has reached mega joule level in the world,and the related research and development of ICF device has begun in China.Compared with Shenguang Series III,Shooting range of ICF device has more beams,larger aperture,more complex optical path arrangement and higher integration level.One of the critical technologies that have a great impact on the structure of the shooting range is the performance of more than 1000 transmission mirrors,which are related to shooting accuracy and energy.The existing mirror support structure of domestic devices cannot meet the requirements of high beam integration and shooting in array of mega joule ICF devices,and the surface accuracy of the mirror cannot meet the requirements.Therefore,the research on the back support of the mirror in ICF devices is carried out to meet the requirements of the key performance such as surface accuracy.In this paper,the large-aperture transmission mirror widely used in ICF is taken as the research object,and the following aspects of work are carried out:(1)Based on an overview of the development of ICF devices and large-aperture mirrors at home and abroad,the main problems and the key technologies in the structural design of large-aperture mirrors in ICF devices are expounded.(2)Based on the mathematical description of the optimization problem of the back support of the mirror,the design of experiment the theory of response surface approximation model and the optimization algorithm are studied,which lay a theoretical foundation for the following design,analysis and optimization work.(3)By studying the influence of mirror's self-weight on mirror's deformation,the peak-valley value(PV value)of mirror shape accuracy is determined as the evaluation criterion of surface error,and the structural optimization of mirror support with minimum PV value of surface accuracy is carried out by response surface optimization method.To solve the problem that the PV value of surface accuracy cannot be used as the objective of finite element commercial software optimization,an optimization platform including finite element model updating,calculation and evaluation is established by using Ansys Workbench software process integration and process automation functions.(4)This paper proposes a two-step optimization strategy.Firstly,the rough precision response surface is established based on the whole design range,and the preliminary optimization results are obtained.Then,based on the preliminary optimization,a high-precision response surface is established to narrow the design range,and the position of support points is further optimized to obtain the optimal support structure.The results show that the optimal solution of response surface optimization is very close to the finite element calculation results at this point,and the error of the direct optimization results on the finite element model is acceptable,but the calculation efficiency has been greatly improved.(5)Through two-step response suface optimization method,the optimal solutions of the mirror surface PV value of the five-parameter mirror model and the three-parameter mirror model are obtained,which can be used to guide to choose the design parameters of the mirror's back support in practical engineering problems.