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Question Gadolinium neutron capture - missing conversion electrons 

Forum: Hadronic Processes
Date: 06 May, 2014
From: Dorothea Pfeiffer <Dorothea Pfeiffer>

Dear colleagues,

I'm trying to simulate the neutron capture of Gadolinium with Geant4.10 on lxplus. As starting point I use the rdecay2 example with the attached macro. My environment variables are in the file env.txt.

I choose the QGSP_BIC_HP physics list. The neutron capture and the generation of prompt gammas work, but I do not see any conversion electrons. The Gd158 does not appear in its excited state, but is already in the ground state after the neutron capture and gamma emission.

*********************************************************************************************************
* G4Track Information:   Particle = neutron,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0        0        0       -5   2.5e-08        0        0         0      Target initStep
    1        0        0    -4.99         0        0  0.00796   0.00796      Target nCapture
    :----- List of 2ndaries - #SpawnInStep=  3(Rest= 0,Along= 0,Post= 3), #SpawnTotal=  3 ---------------
    :         0         0     -4.99      5.87              gamma
    :         0         0     -4.99     0.997              gamma
    :         0         0     -4.99  8.48e-05              Gd158
    :----------------------------------------------------------------- EndOf2ndaries Info ---------------

*********************************************************************************************************
* G4Track Information:   Particle = Gd158,   Track ID = 4,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0        0        0    -4.99  8.48e-05        0        0         0      Target initStep
    1 -4.17e-11 -5.9e-11    -4.99         0 8.48e-05 3.36e-06  3.36e-06      Target ionIoni
    2 -4.17e-11 -5.9e-11    -4.99         0        0        0  3.36e-06      Target RadioactiveDecay

*********************************************************************************************************
* G4Track Information:   Particle = gamma,   Track ID = 3,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0        0        0    -4.99     0.997        0        0         0      Target initStep
    1 -0.00155 -0.000766       -5     0.997        0  0.00815   0.00815  OutOfWorld Transportation

*********************************************************************************************************
* G4Track Information:   Particle = gamma,   Track ID = 2,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0        0        0    -4.99      5.87        0        0         0      Target initStep
    1    0.932     1.16        5      5.87        0     10.1      10.1  OutOfWorld Transportation

I tried to the SetICM flag in the radioactive decay and modified the physics list of the example

G4RadioactiveDecay* radioactiveDecay = new G4RadioactiveDecay(); radioactiveDecay->SetHLThreshold(nanosecond); radioactiveDecay->SetICM(true); //Internal Conversion radioactiveDecay->SetARM(true); //Atomic Rearangement G4PhysicsListHelper* ph = G4PhysicsListHelper::GetPhysicsListHelper(); ph->RegisterProcess(radioactiveDecay, G4GenericIon::GenericIon());

But this also did not produce conversion electrons. I assume because after the neutron capture, the Gd158 is already in its final state.

On the other hand, if for test purposes I directly fire an excited Gd158

/gps/particle ion /gps/ion 64 158 0 2000 keV

I do get conversion electrons. That proofs that the ENDF files contain data entries for the decay of the excited 158Gd.

Any help would be highly appreciated!

Cheers

Dorothea

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/05/06/02.23-99293-Gd_neutron.mac
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/05/06/02.23-37719-env.txt

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