[Gate-users] possibly a bug in ROOT output

[nehmehs at MSKCC.ORG]

Dear All,

I am afraid there is a tiny bug when writing the hits file. I have a 511 kev gamma source irradiating scintillation crystal. The gamma information in the root file look like they are lagging by one entry compared to the geant track output. In the example below, the gamma goes into two compton interactions; the 1st at X=201 mm and the 2nd at X=182 mm. The positions at which the compton scatters occur are  however written in the root file as X=130 mm (this corresponds to the  step " crystal_phys Transportation" which preceded the 1st compton interaction) and the X=201 mm (this corresponds to the 1st interaction rather than the 2nd). Am I missing smth?

Thanks,

Sadek


Root output:
************************************************************************************
*    Row   *   eventID * nCrystalC * PDGEncodi *      posX * processNa *      edep *
************************************************************************************
*        7 *         5 *         1 *        22 *       130 *   Compton *         0 *
*        8 *         5 *         2 *        22 * 200.95007 *   Compton *         0 *
*        9 *         5 *         2 *        11 * 182.13983 * ElectronI * 0.0747875 *
*       10 *         5 *         2 *        11 * 200.95007 * ElectronI * 0.3246354 *
************************************************************************************

Geant output for the same event:
 *********************************************************************************************************

[G4] * G4Track Information:   Particle = gamma,   Track ID = 1,   Parent ID = 0

[G4] *********************************************************************************************************

[G4] 

[G4] Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName

[G4]     0        0        0        0     0.511        0        0         0 scanner_phys initStep

[G4]     1      130        0        0     0.511        0      130       130 crystal_phys Transportation

[G4]     2      201        0        0     0.186        0       71       201 crystal_phys Compton

[G4]     3      182    -3.38    -16.7     0.112        0     25.4       226 crystal_phys Compton

[G4]     4      230     15.2    -8.08     0.112        0     52.1       278 scanner_phys Transportation

[G4]     5      250       23     -4.5     0.112        0     21.8       300  world_phys Transportation

[G4]     6    2e+03      704      309     0.112        0  1.9e+03   2.2e+03  OutOfWorld Transportation

[G4] 

[G4] *********************************************************************************************************

[G4] * G4Track Information:   Particle = e-,   Track ID = 3,   Parent ID = 1

[G4] *********************************************************************************************************

[G4] 

[G4] Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName

[G4]     0      182    -3.38    -16.7    0.0748        0        0         0 crystal_phys initStep

[G4]     1      182     -3.4    -16.7         0   0.0748   0.0846    0.0846 crystal_phys ElectronIonisation

[G4] 

[G4] *********************************************************************************************************

[G4] * G4Track Information:   Particle = e-,   Track ID = 2,   Parent ID = 1

[G4] *********************************************************************************************************

[G4] 

[G4] Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName

[G4]     0      201        0        0     0.325        0        0         0 crystal_phys initStep

[G4]     1      202   0.0348    0.172         0    0.325    0.926     0.926 crystal_phys ElectronIonisation

 
 
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