The design of the small prototype for the central detector of JUNO

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) is a multipurpose neutrino experiment designed to determine neutrino mass hierarchy, precisely measure oscillation parameters and study solar neutrinos, supernova neutrinos and geo-neutrinos. The JUNO Central Detector 20 kton liquid scintillator target mass is contained by a huge acrylic sphere with a 35.4 m inner diameter, supported by a stainless steel structure, and the sphere is eventually submerged in pure water. Before the JUNO Central Detector is built, a small prototype has been designed and static loading experiments will be carried out to verify the consistency of the finite-element calculations and static loading experiments and test the subsystems performances, such as the monitoring system and liquid scintillator filling system. The small prototype is composed of an acrylic sphere with a 3 m inner diameter and an aluminum alloy support structure. In this article, the structure of the small prototype is briefly described. A detailed simulation study using finite element analysis is conducted to account for liquid-filled condition, temperature variation and existence of high load (due to vacuum pumping) and demonstrate a satisfying mechanical performance of the small prototype. The experimental plan about the prototype on the basis of the simulation will also be mentioned.