Analysis of the Effect of Ambient Loads on the SG-III TIL Structure Stability

ICF (Inertial Confinement Fusion) drivers are large-scale precision optical facilities. Structure stability is an important design index for ICF drivers and it has a direct influence on the quality of beam shooting. The total positioning error budget designed for the SG-III Technical Integration Experiment Line (TIL) built in China is 30 micrometers (μm) at the target plane or its equivalent, among which the allocated stability budget is 27μm and the translation of a single optical element should be less than 1μm under the effect of ambient loads. Based on the previous evaluation of the TIL environment, the microvibration and thermal load are two main factors which can affect stability of the optical system. To obtain the data of the two ambient loads, acceleration seism sensors and high precision temperature sensors are used to measure the ambient vibration and temperature change for a long time. The finite element model is then built for a typical optical element and its support structure and the measured loads are exerted on the model to obtain the response of the optical system. The results show that both stability of a single optical element and stability of the laser beam can satisfy the designed index. This research is very helpful for the building of the SG-III main facility.