The collection efficiency depends on where a photo-electron is emitted
on the photo-cathod surface. The above figure shows our scan results
of IceCube PMT(TA2026).
Two figures below show the relative efficiency in two azimuthal angle slices (0deg and 90deg) for TA2026. The efficiencies plotted here are normalized so that the average efficiency over entire photocathode is 100 %. You can see the efficiency varies photon locations to locations by +- 20 %. The difference between different tubes is also visible. We will implement these effects to the IceCube detector MC.