Generation of photon in mother logical volume


I am new to Geant4 and am trying to describe my problem as thoroughly as possible. I have built a custom geometry of a PhotoMultiplier Tube (PMT) consisting of roughly 20 logical volumes inside a mother logical volume, which is a simple cube with dimensions of 0.5m x 0.5m x 0.5m.

Now, using this PMT as a baseline, I am creating 19 copies in different .cc files, placing them on a support structure inside another mother volume—a cube with dimensions of 1m x 1m x 1m. Each PMT is positioned at different locations and angles on a hemisphere object.

I am facing two problems here:

  1. Each PMT is coming with a logical volume, i.e., a cube with dimensions of 0.5m x 0.5m x 0.5m. How can I eliminate this local mother volume?
  2. When I am generating a photon in the mother logical volume, it’s not interacting with my geometry and is choosing an arbitrary direction, even though I am generating it perpendicular to my geometry at zero degrees. I suspect the particle is being generated with respect to the local mother volume.

Please let me know how I can instruct my generator to generate photons in the mother physical volume.