Optimization of large-aperture optics clean assembly method

The contamination on optical surface is an important factor that causes laser-induced damage. In the assembly process of the SGIII, the traditional manual assembly method poses a great challenge in terms of the cleanliness of optical components. So the contamination introduced by the manual assembly is studied including particulate and non-volatile residue (NVR). The use of vacuum system device to clamp is an important means to achieve automated clean assembly. The contact contamination is the main source of contaminants in the vacuum-clamping process. One source is the organic residue left on the optical surface, by comparing the residue of different sealing rubber after absorbing the optics, we find that FPM (fluorine rubber) brings the least contamination. The second source is the coating debris causing by the compressive and shear stress on the optical surface during the vacuum clamping process. We have established a theoretical model, through the numerical simulation method to obtain the stress under different assembly conditions. For different optical films, the stress during the assembly process cannot exceed the fatigue limit of the optical coating to prevent the film from being destroyed and debris contamination. The cleanliness level of the vacuum clamp assembly process is evaluated through experiments. The results show that the contamination generated by assembling large-aperture optics with a vacuum gripper meets the optical surface cleanliness requirements.