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None Gamma emission from Pa234 and alpha decay energy  

Forum: Hadronic Processes
Date: 20 May, 2015
From: Young Soo Yoon <Young Soo Yoon>

While I work on decays of U238 and daughter particle, I found some strange events with higher deposited energies that Q-values, from Th234 to Pa234. In the log, a gamma was emitted at Pa234[186.7] state and it remain at the sate state. Lots of gamma were emitted at the same state in one event. Some part of log are below.

* G4Track Information:   Particle = Pa234[186.7],   Track ID = 68,   Parent ID = 64

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0     26.6     73.4    -65.3         0        0        0         0 CMOPhys initStep
    1     26.6     73.4    -65.3         0        0        0         0 CMOPhys RadioactiveDecay
    :----- List of 2ndaries - #SpawnInStep=  3(Rest= 3,Along= 0,Post= 0), #SpawnTotal=  3 ---------------
    :      26.6      73.4     -65.3         0       Pa234[186.7]
    :      26.6      73.4     -65.3   0.00286                 e-
    :      26.6      73.4     -65.3     0.109              gamma
    :----------------------------------------------------------------- EndOf2ndaries Info ---------------
Track (trackID 68, parentID 64) is processed with stopping code 2

Among 10^6 events of U238 decay, 3095 events (~3%) showed this behaviour. Specially, it happened whenever decay product from Th234 was Pa234[177.3] and Pa[186.7] in GEANT 4.9.6. When I run in GEANT 4.10.0, events with those behaviour were reduced quietly, (0.014%), but some events still showed similar behaviour, when decay product of Th234 is Pa234[182.27]. Levels and intensity of Pa234 in Radioactive Decay files kept changed from 3.6, 4.0, and 4.2.

I thought, migration to GEANT 4.10.0 might be an alternate solution. However, I noticed that energy of alpha particle in alpha decay has ~40keV higher energy than result from GEANT 4.9.6. I think, it might be the same issue reported earlier (message 1415). I havn't tested this yet in GEANT 4.10.1, but I couldn't fine any updated information about Hadronic Process in GEANT 4.10.1 release note. I hope these to be fixed in next patch or version release.


Young Soo

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