Research on thermoforming process of JUNO large acrylic spherical panel

Introduction Jiangmen Underground Neutrino Observation (JUNO) focuses on determining neutrino mass hierarchy and other physical purposes. The central detector is one of the keys to the JUNO. The main structure of the central detector is an acrylic spherical container with a diameter of 35.4 m, which will be the largest acrylic spherical vessel in the world. Its construction will inevitably face many great challenges and difficulties. Method The thermoforming process of large acrylic spherical panel is introduced, which is a very important step in panel production. The effect of temperature on the curvature of panel during thermoforming is discussed. The thermal deformation of panel in thermoforming process is analyzed by finite element method. The bending experiment and curvature measurement are carried out, and the influence of deformation of the panel under gravity on the curvature of the panel is analyzed. Results The current thermoforming process makes the curvature of panel smaller than that of mold. The measurement results show that the curvatures are different due to the influence of gravity when the panel is placed on the mold or vertically. Some suggestions for improving the shape of spherical panels are put forward. In the thermoforming process, the temperature of the concave–convex surfaces of the panel should be controlled at the same level as far as possible. Another feasible method is to increase the radius of the forming mold to obtain a spherical panel with designed radius.