Mechanical design of multi-PMTs for IWCD

Approximately 500 multi-PMTs (mPMTs) will be used as the photosensors for Intermediate Water Cherenkov Detector (IWCD), a new near detector approved Hyper-Kamiokande experiment that built by 2025. The IWCD mPMT design has nineteen 3” PMTs enclosed in water-tight pressure vessel, along with associated electronics. provide excellent spatial imaging of neutrino-induced light ring. This work focus on mechanical vessel. In particular, acrylic dome, use optical gel to couple dome PMTs, assembly procedures and PMT sub-assembly (including necessary jigs / fixtures), feed-through & plans testing results from several prototypes.