A question about useless sheild

[F-xy520]

I want to simulate such a system:A source at the middle ,and a wall made of iron beside it,I put 64 detector around them to show the influce the wall make to the transmit of particles.
But I find that the wall make no influence,and my detector almost receive no signal.
What's wrong with my settings.If anyone could tell my the reasons,I'll be very gratefull.
egsinp.txt

[rtownson]

You have your detectors inside world_box, but then try to envelope everything into world_box again.

:start geometry:
    name = all_detectors
    library = egs_genvelope
    base geometry = world_box
...

:start geometry:
    name = full_geometry
    library = egs_genvelope
    base geometry = world_box
    inscribed geometries =  all_detectors iron_wall
:stop geometry:

This is not allowed, because all inscribed geometries must be entirely inside the base geometry, and must not be touching other inscribed geometries. Instead of using world_box as the base geometry for all_detectors, create a smaller box just around the detectors. Or better, just place all your detectors inscribed into world_box at the same time as iron_wall, without the intermediate step.

Use egs_view to confirm that it looks correct. If you looked at the input file you sent, you would see that iron_wall was not visualized.

[F-xy520]

Thank you. It is solved.