Can detector acts as its own "source"?

[kitu.utkarsh]

Hello all,

I have a really silly question,

Suppose I make a cylindrical crystal and assign its material as 60Co (or any radioactive ion). I make this my scoring volume to deposit the energy absorbed.
Just a clarification, this is not my source, as in not defined in the event generator but rather in detector construction. The relevant G4Radioactive and G4Decay classes have been included in the physics list.

When I run the simulation will this material undergo radioactive decay and also contribute to the resulting spectra?

Can someone please share their thoughts on the same?

Thanks in advance!

[kitu.utkarsh]

I think I have got my answer from

Decay of Cobalt 60 in slab

You’ve discovered the difference between G4Isotope, which is part of the G4Material framework for defining geometry elements, and G4Ions, which are active trackable particles corresponding to nuclei. You can make your geometry out of anything you want. It won’t decay. It won’t get activated. It’s absolutely passive stuff which is identical from event to event in your simulation. It’s the “ground” within which all the tracks do their thing. If you want to generate events simulating Co-60 de…

[mkelsey]

You found the correct answer. It is possible to use GPS to specify a region of the world (a “volume”, but not a true G4LogicalVolume) within which to generate events. You could set up your GPS so that the source region corresponds to your “detector crystal”, and throw Co-60 decays in that region.

In our experiment, we are very concerned about radiocontaminants in both the support structures and the detectors themselves, and this is the main way we generate simulated events. We wrote code where you can pass in a specific G4 volume by name (either LV or PV), and it picks random positions in the corresponding G4VSolid for each event.

[kitu.utkarsh]

Thanks, Michael,
Yes, this approach is quite helpful of “overlapping” source and detector regions is quite helpful.
Just a follow up though are there any examples/codes that achieve the tasks of simulating decays uniformly inside a given region (cylindrical or other geometry)?
Thanks

[mkelsey]

Looks like there are several. I used the commands

cd <g4-source-dir>/examples
find . -name '*.mac'|xargs grep -l '/gps/.*Volume'

and got 26 different file matches, covering four examples. You should look at them yourself and see which one best aligns with the kind of simulation you want to do.

[maire]

In particular examples/extended/radioactivedecay/Activation

error !
extended/hadronic/NeutronSource

[kitu.utkarsh]

Thanks a lot, @maire. I will look for this example.