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None Example Hadr03: Conversion electrons and gammas after neutron capture incorrect 

Forum: Hadronic Processes
Date: 27 Sep, 2016
From: Dorothea Pfeiffer <Dorothea Pfeiffer>

Hi,

using the attached macro file for example Hard03 in Geant4 10.2.p02 (PhotoEvaporation3.2), I get 2 possible nuclear reactions for the neutron capture in Gd:

List of nuclear reactions:

                    neutron + Gd --> N gamma + Gd158:   27338   Q =  7.9374 MeV
               neutron + Gd --> N gamma + e- + Gd158:   72281   Q =  7.9161 MeV
                    neutron + Gd --> neutron + Gd157:     381   Q = 0.038964 eV 

                                     Number of gamma: N = 1 --> 2

Together with the flag G4NEUTRONHP_USE_ONLY_PHOTONEVAPORATION=1, I get the particles below. There are conversion electrons, but only from the first excitation level. The other levels are missing. For all other levels I get only gammas. In total, compared to the literature, the number of conversion electrons is slightly too high and the number of gammas too low.

List of generated particles:
          Gd157:     381  Emean = 0.038891 eV ( 0.00096043 eV  --> 0.19133 eV )
          Gd158:   99619  Emean =  210.68 eV  ( 194.17 eV  --> 226.3 eV )
             e-:   72281  Emean =  58.253 keV ( 29.264 keV --> 79.148 keV)
          gamma:  111468  Emean =  7.0419 MeV ( 79.508 keV --> 7.9372 MeV)

In Geant4 10.1 (PhotoEvaporation3.2) on the other hand, there were nuclear reactions with 2,3 and 4 conversion electrons, that are missing in the newest Geant4 version.

List of nuclear reactions:

          neutron + Gd157 --> N gamma + 2 e- + Gd158:    8465   Q =  7.9374 MeV
          neutron + Gd157 --> N gamma + 3 e- + Gd158:      22   Q =  7.9374 MeV
          neutron + Gd157 --> N gamma + 4 e- + Gd158:       1   Q =  7.9374 MeV
                 neutron + Gd157 --> N gamma + Gd158:   56274   Q =  7.9374 MeV
            neutron + Gd157 --> N gamma + e- + Gd158:   34882   Q =  7.9374 MeV
                 neutron + Gd157 --> neutron + Gd157:     356   Q = 0.035456 eV 

                                     Number of gamma: N = 2 --> 7

The generated particles in Geant4 10.1 contained also conversion electrons from higher levels, and lower energetic gammas. Further, the total number of conversion electrons was correct in Geant4 10.1 compared to the literature, and also the number of gammas.

 List of generated particles:
          Gd157:     356  Emean = 0.035851 eV 	( 0.0007276 eV  --> 0.16493 eV )
          Gd158:   99644  Emean =  106.47 eV 	( 0.018335 eV  --> 227.05 eV )
             e-:   51882  Emean =  56.753 keV	( 29.264 keV --> 1.1358 MeV)
          gamma:  242211  Emean =  3.2532 MeV	( 7.2426 keV --> 7.3982 MeV)

What has been changed in the latest version? Where have the nuclear reactions that produced 2,3 or 4 conversion electrons gone to? For me it looks like that in Geant4 10.2.p02 the excited 158Gd now de-excites down to the first excitation level, and for this level always produces a K,L or M shell conversion electrons. Somehow the ICC in the PhotoEvaporation3.2 data are ignored.

Cheers

Dorothea

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2016/09/27/06.06-80996-nCaptureGd.mac

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