Radioactive decay Am-241 and Pb-210

Physics Processes, Models and Cross Sections
1

Hello, I simulated the radioactive decay of some radionuclides (Am241, Co60, Cs134, Cs137, Pb-210).
My tutor said that the deposited energy in the crystal by C060, Cs134 and Cs137 are good, while the Am241 and Pb210 are wrong). There is a problem in Geant4 for these radionuclides. My tutor said me that Am241 and Pb210 have radioactive sons then he think that maybe GEANT4 simulates all the decays instead of just Am241 and Pb210.
Does anyone know something about the simulation of these two radionuclides and how to fix??

Here the obtained spectra

Am241

DepositedEnergy_logy
DepositedEnergy_logy1276×996 8.59 KB

Pb210

DepositedEnergy_logy
DepositedEnergy_logy1276×996 8.06 KB

2

You simulated these radioactive decays but didn’t mention how you specified the radionuclides. Did you use /gps/ commands in a macro?
In the past I had the opposite problem, i.e. the decay of (very) long-living states ‘polluted’ my spectrum, therefore, I think Geant4 simulates the full decay chain. But you should be able to easily check this yourself using the tracking verbosity.

3

Hello @svanlang , yes I use a macro to define the radionuclides:

/gps/particle ion
/gps/ion 82 210 0 0
/gps/energy 0. eV

I found this old topic Incorrect Am241 decay spectrum and I read @mkelsey reply in wich he suggested to limit the radionuclide by the /grdm/nucleusLimits command then I added in my code

for Pb210
/grdm/nucleusLimits 210 210 82 82

and for Am241
/grdm/nucleusLimits 241 241 95 95

and now I get

for Pb210

Pb210
Pb2101276×996 6.06 KB

and Am241

Am241
Am2411276×996 7.12 KB

I’m almost sure about Pb210 because on Table of Isotopes decay data I read only a peak at 45.5keV…
Regarding the Am241 I’ve some doubts because on Table of Isotopes decay data it gives so many peaks. Nevertheless, the Igamma% is at energy 59.6keV and I see a peak for this energy value.

I also tried to follow the radioactivedecay example, as suggested by @maire , then:

  1. I wrote trackingaction.cc , trackingaction.hh, trackingmessenger.cc, trackingactionmessenger.cc

TrackingAction.cc (3.9 KB)
TrackingMessenger.cc (2.9 KB)

  1. I added the code in actionvisualization
  TrackingAction* trackingAction = new TrackingAction(eventAction);
  SetUserAction(trackingAction);

B1ActionInitialization.cc (3.1 KB)

  1. I added in the macro

/rdecay01/fullChain false

Using this method, I don’t get errors during compiling and method, but I don’t get the deposited energy.

Thank you

1 Like
4

I also faced the similar issue with Am-241 and have not resolved it yet. The scheme works well for Cs-137, Eu-192 etc, didn’t try Pb-210 though. Even with FLUKA this issue is there for Am-241.

5

Hi, this macro command worked fine for me (my boss confirmed it)

/grdm/nucleusLimits 241 241 95 95

i.e. you have to limit the simulation only to the Am241 decay, without simulating its sons.

6

I am not sure if you have solved it yet. The reason why Am giving very high energy lines might be due to the spontaneous fission of 241Am. Again as mentioned by so many others in this post /grdm/nucleusLimts can solve the problem I think