Study on dimensional metrology of EAST vacuum vessel internal components

In this paper, a high precision measurement network was built with 64 fiducials placed on the EAST vacuum vessel(VV) inner surface for dimensional metrology of internal components. Unified Spatial Metrology Network(USMN) analysis showed that the average uncertainty of this network can be less than 0.15mm. The three coordinate flexible measuring system was used to do the dimension inspection in VV and with leapfrog type transfer station method to confirm there were no blind areas of measurement. During the whole assembly process of VV inner components, the different temperature and gravity distribution would make the VV inner surface get different deformations which will produce small drift to the coordinate system of the measurement network. Mechanical analysis was done to get the deformation distribution of the VV during the assembly process, the analysis results were compared with the actual measured values to estimate the authenticity of this variation. Base on the above research, the coordinate system of the measurement network was corrected by different compensation during different assembly stage to obtain higher measurement accuracy.