PMT assembly
The goal is to couple the lens onto the PMT face with oil
Seal the edge of the PMT face to the PMT housing with 5 min epoxy - careful not to soil the plate above the photocathode
Add 30 - 50 ul of high viscosity oil
Place condensor lens on oil. Make sure there are no bubbles and carefully remove overflow oil from the housing.
Place a thin ring of quick seal (WPI) on the PMT housing around the lens