The 40cm long target cell is at the top of the image. The green lines indicate lines-of-sight through the detector stack. They are probably generous in that they intersect with the middle of the pole face rather than the downstream edge.
Note that the Cerenkov PMTs should be well shielded from the endcaps by the BigBite yoke (>60cm of steel). The front face of the PMTs used to be flush with the cylinders you can see in this model. They were shifted 12.5 cm farther back (along the cylinder axis) to accommodate the additional magnetic shielding.
The witness PMT is on the beam-left side of the model, roughly centered on the light-blue platform and just to the beam-left of the Cerenkov PMTs. It should also be well shielded from the target.
So what's producing the (apparent) shower into the Cerenkov PMTs and the
witness PMT? Thoughts?
A copy of this log entry has been emailed to: meziani, jiang, bogdanw, jpchen