Dear All,
I have a problem with the free neutron lifetime. The setup involves a target of Galactic in a world of Galactic.
I do not See a decay of cirka 15 mins for neutrons of various low energies. Can anyone help me here. Actually Ive never seen this. Is there physics that I am missing.
best wishes, David Batchelor
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Gean4 11.4
Tahoe 26.3
XCode 26.0
CMake 4.0.3
What is your physics list and primary generator/macro look like? A truly thermal neutron is moving at about 2 km/second which would require a world that 1800 kilometers in size
Hallo Jrelin,
thanks for the pointers, food for thought (I used .1 meV neutrons to be sure it was in the volume). The decay was on as I changed the target volume and could activate the material and saw nice activation and decay (but didn’t see anything at start?). Anyway I will look again at the hadronic examples.
thanks again for your reply and jolting me from my present orbit :-).
Using the Physics list from the NeutronSource example improved the behaviour. I now have neutrons decaying at non zero kinetic energy with a correct lifetime. Don’t understand it fully- I believe I should see more decay for higher energies. But this has helped and will investigate further.
best, David.
Pushing the World volume up to 1E-4 A.U.^3 has made things accessible/clearer- difficult to do in the Lab 
thanks for the feedback