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Warning Neutron Capture bug? Too many gammas 

Forum: Hadronic Processes
Date: 25 Apr, 2011
From: Manuel Julien <Manuel Julien>

Hi,

I'm working on thermal neutron capture on Boron 10. Most of the times, the reaction is 10B + n -> 7Li + alpha + gamma, which is well handled by the inelastic neutron process. I am talking here about the "real" neutron capture reaction 10B + n -> 11B* -> 11B + gammas, which his handled by the neutron capture process and maybe also photon evaporation. In the reaction 10B + n -> 11B*, the 11B* has 11.45 MeV to release. The problem is that the summed energies of the gammas produced by the neutron capture process is way over what is available, although the energies of the gammas are right in the sense that they are allowed transitions. Here are two examples :

First example (Tracking verbose set to 2) :

********************************************************************************************
* 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     -200      -87      -19   2.5e-08        0        0         0       World initStep
    1     -105      -87      -19   2.5e-08        0       95        95        AC_1 Transportation
    2     -104      -87      -19         0        0     1.01        96        AC_1 nCapture
    :----- List of 2ndaries - #SpawnInStep=  6(Rest= 0,Along= 0,Post= 6), #SpawnTotal=  6 --
    :      -104       -87       -19      4.71              gamma
    :      -104       -87       -19      4.71              gamma
    :      -104       -87       -19      4.44              gamma
    :      -104       -87       -19      4.45              gamma
    :      -104       -87       -19      4.45              gamma
    :      -104       -87       -19   0.00271           B11[0.0]
    :----------------------------------------------------------------- EndOf2ndaries Info --

Total gamma energy : 22.76 MeV

Second example (Tracking verbose set to 3) :

         Step Status         :            Undefined       PostStep Proc
         Process defined Step:            Undefined            nCapture
      -----------------------------------------------------------------------

    ++List of secondaries generated (x,y,z,kE,t,PID):  No. of secodaries = 6
      [Note]Secondaries from AlongStepDoIt included.
      -96.15731357144018 31.66011610716351 -22.93675300945488 8.920013346214214 50530.5323918245              gamma
      -96.15731357144018 31.66011610716351 -22.93675300945488 7.010987880020568 50530.5323918245              gamma
      -96.15731357144018 31.66011610716351 -22.93675300945488 7.011013572663825 50530.5323918245              gamma
      -96.15731357144018 31.66011610716351 -22.93675300945488 4.713002275090939 50530.5323918245              gamma
      -96.15731357144018 31.66011610716351 -22.93675300945488 4.712990775011796 50530.5323918245              gamma
      -96.15731357144018 31.66011610716351 -22.93675300945488 0.00114230216058786 50530.5323918245           B11[0.0]

Total gamma energy : 32.368 MeV

Here are references for 11B nuclear energy levels, the gammas should not have more than 11.45 MeV :

http://www.tunl.duke.edu/nucldata/TNC/11B.shtml
http://www.tunl.duke.edu/nucldata/figures/11figs/11_05_1990.gif

Manuel

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1 Idea: Re: Neutron Capture bug? Too many gammas   (Vladimir Ivanchenko - 28 Apr, 2011)
1 Feedback: Re: Neutron Capture bug? Too many gammas   (Manuel Julien - 29 Apr, 2011)
(_ Idea: Re: Neutron Capture bug? Too many gammas   (Vladimir Ivanchenko - 10 May, 2011)
2 None: Re: Neutron Capture bug? Too many gammas   (Koi, Tatsumi - 29 Apr, 2011)
1 Feedback: Re: Latest 4.9.4.p01   (Manuel Julien - 02 May, 2011)
3 News: Neither QGSP_BERT_HP or QGSP_BIC_HP work   (Manuel Julien - 10 May, 2011)
4 None: Re: Neutron Capture bug? Too many gammas   (Koi, Tatsumi - 10 May, 2011)
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