PMT Simulation

This section of the manual will outline how the PMT-reflector arrangement has been implemented into SNOMAN. The operation of the PMt code is analogous to that of the rest of SNOMAN, though for reasons of speed, the ZEBRA data structure is not used. The code has two "processors'' - a track processor, which queries the PMT geometry routines to determine which surface is struck next, and a vertex processor which determines what will happen at that boundary. The photon is followed until one of the following occurs:

• A hit is scored.

• The photon exits the front face of the model, and is returned to the jurisdiction of the main code.

• The photon is absorbed; this can happen at any of the boundaries with omega, aluminium or photocathode material. In this case the photon does not score a `hit'.

• The photon is lost. Certain degrees of complexity (see the User manual) do not include the internal structure of the PMT. Any photon entering that area is then deemed to be lost.

The geometry is essentially a set of spheres toroids and cylinders. Please note that the discussion may be a little difficult to follow as it relies on a number of postscript diagrams, and it is not currently clear to me that everyone uses postscript, or that the system for incorporating such pictures is the same everywhere. Anybody interested can mail me (m.lay1@uk.ac.ox.physics) and I will send them out.