Unexpected β spectra of Pb210 using G4 example rdecay01

Physics Processes, Models and Cross Sections
1

Hi,

I’m encountering an issue when using the Geant4 example rdecay01 to simulate the beta spectra of Pb210. Specifically, I’ve noticed that one of the decay products, Bi210[46.539], always has a kinetic energy of 0 keV, which seems physically unrealistic during a decay process.

Macro File:

/control/cout/ignoreThreadsExcept 0
/control/verbose 2
/run/verbose 1

/process/had/rdm/thresholdForVeryLongDecayTime 1.0e+70 year

/gun/particle ion
/gun/ion 82 210

/rdecay01/fullChain false

/analysis/setFileName run1
/analysis/h1/set 1 100 0. 100 keV #e+ e-

/run/printProgress 10000
/run/beamOn 100000

In this simulation, the Bi210[46.539] decay product is consistently assigned a kinetic energy of 0 keV, which I find puzzling because I expected it to have some kinetic energy after decay. This issue seems to persist regardless of the number of events or other settings in the macro file.

Has anyone encountered a similar issue or could provide some insight into why this might be happening? Is there something I might be overlooking in the setup, or could it be related to how the decay process is being handled in the rdecay01 example?

Any guidance or suggestions on how to resolve this issue would be greatly appreciated!

Thank you!

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Geant4 Version: 11.2.2
Operating System: Windows 11
Compiler/Version: MSVC 19.39.33523
CMake Version: 3.29.3

2

With other macros in rdecay01, you can see that kinetic energy of secondaries is non null in all cases, as far as I can see …
Therefore the problem, if any, is not in rdecay01 itself.
Maybe, in data set, either RadioactiveDecay or PhotonEvaporation, of Pb210 or Bi210 …

3

I have tried modifying the RadioactiveDecay parameters for Pb210, for example changing the intensity and even removing all other levels, leaving only Bi210[46.539]. Despite these changes, the kinetic energy of Bi210[46.539] still remains 0.

Additionally, I’m unsure why PhotonEvaporation would be relevant in this simulation. As I understand it, this simulation focuses on the beta decay process, and gamma decay should have little influence on the kinetic energy of the decay products.