Experimental and numerical study on implosion protection of large format photo-multiplier tubes

As the hollow structures are prone to implosion in deepwater environments, which will result in catastrophic accidents, the implosion protection of photo-multiplier-tubes (PMTs) is an important issue in the design and operation of large format underwater neutrino detectors. In this paper, the implosion protection of dense layout large format PMT was investigated, and the implosion protective device was designed. Specifically, the steel-made compressive sealed container was used to simulate the deepwater environment, and the PMT implosion experiment was carried out at a water depth of 40 m. The underwater implosion process and flow field pressure were recorded. The experimental results showed that the protective device could significantly reduce the shock wave intensity generated by the implosion and diminish the occurrence of large-scale sympathetic implosion. In order to reveal the protection design mechanism, the PMT implosion simulation was carried out. The calculation results showed that the peak pressure of the shock wave generated by the implosion decreased as the hydrostatic pressure, the area and the impact angle of the water flow reduced respectively. Then, the empirical formula of hydrostatic pressure and the area of water flow with the peak of the shock wave pressure were obtained. This study laid a solid foundation of guidance for the engineering implosion protection design of large format PMT and other deepwater hollow structures.