Ionization and Number of the the electrons produced

Introduction

Fission reactions produces fragments of different energies, these fragments interact with the medium and causes ionization. Fission fragments stopped by the medium in different ranges, the range is dependent on the following :

1- Mass of fission fragments

2- Charge.

3- Kinetic energy gained after the fission reaction.

4- The medium surrounding the fission fragments.

The aim of this study to calculate the number of electrons produced by the fission fragments travels in a gas chamber has an electric field (E).

In this study the fission fragment will treated as ions without any electrons surrounding the nucleus.

Ion Interactions with matter

As the ion is traveling through the material, it causes a number of interactions because of Energy loss, like energy struggling , charge exchange, and multiple scattering. those interactions help in determining the energy dispersion, range and emittance. The previous interactions take place in gas chamber of the detector and produce electrons. This electron multiplication occurs inside an electric field area, the electric field is responsible for collecting the electrons, so the detected total charge density of the electrons depends on the electric field.

GEANT4 Simulation

Geant4 is adjusted to have a chamber that contains Ar (90 percent) ands CO2 (10 percent). as the beam runs, the fission fragments are produced but the effect of the ionization does not appear, i.e there are not any electrons tracked by geant4 after ionizing the gas by the fission fragments. the follwing is the result of a 10 MeV neutron beam fired on 1 um Th target twice, the first time 1M neutrons fired and the 2nd 2M neutrons fired.

10	1   0   0.333764   6.1989   -1.1297   -24.2403   1.01235   0   1   0   0.333764   6.1989   -1.1297   -24.2403   774930   0   
10	1   0   5.67408   -63.8003   46.5152   66.7862   0.57652   0   1   0   5.67408   -63.8003   46.5152   66.7862   116133   0   
10	1   0   0.349451   -21.6604   -6.25107   -12.1876   0.177055   0   1   0   0.349451   -21.6604   -6.25107   -12.1876   887380   0   
10	1   0   0.43515   4.9144   -27.8918   3.97335   0.512674   0   1   0   0.43515   4.9144   -27.8918   3.97335   769016   0   
10	1   0   0.429285   -9.55169   -4.57634   -26.357   0.0494969   0   1   0   0.429285   -9.55169   -4.57634   -26.357   808294   0   
10	1   0   1.57973   -24.2319   -14.5394   46.6094   1.09783   0   1   0   1.57973   -24.2319   -14.5394   46.6094   87708.7   0   

In both cases SteppingVerbose is changed to detect every particle produced by geant4 but not Th-nuclei.

 
10	1   0   0.333764   6.1989   -1.1297   -24.2403   1.01235   0   1   0   0.333764   6.1989   -1.1297   -24.2403   774930   0   
10	1   0   5.67408   -63.8003   46.5152   66.7862   0.57652   0   1   0   5.67408   -63.8003   46.5152   66.7862   116133   0   
10	1   0   0.349451   -21.6604   -6.25107   -12.1876   0.177055   0   1   0   0.349451   -21.6604   -6.25107   -12.1876   887380   0   
10	1   0   0.43515   4.9144   -27.8918   3.97335   0.512674   0   1   0   0.43515   4.9144   -27.8918   3.97335   769016   0   
10	1   0   0.429285   -9.55169   -4.57634   -26.357   0.0494969   0   1   0   0.429285   -9.55169   -4.57634   -26.357   808294   0   
10	1   0   1.57973   -24.2319   -14.5394   46.6094   1.09783   0   1   0   1.57973   -24.2319   -14.5394   46.6094   87708.7   0   
10	1   0   0.586143   31.2118   -10.8034   -3.30112   0.531741   0   1   0   0.586143   31.2118   -10.8034   -3.30112   797617   0   
10	1   0   0.33299   -18.3319   13.3851   10.5179   0.682332   0   1   0   0.33299   -18.3319   13.3851   10.5179   1.0235e+06   0   
10	1   0   0.361038   25.9736   0.627582   1.88285   0.501458   0   1   0   0.361038   25.9736   0.627582   1.88285   752191   0   
10	1   0   0.272656   13.6254   -8.25379   -16.0827   0.603347   0   1   0   0.272656   13.6254   -8.25379   -16.0827   1.05565e+06   0   
10	105   42   75.3375   -2860.35   127.919   2555.86   0.670899   42   105   42   75.3321   -2860.25   127.926   2555.76   8606.03   42   
10	1   0   0.777481   -4.13192   -23.5454   29.8351   0.811851   0   1   0   0.777481   -4.13192   -23.5454   29.8351   96105.8   0   
10	104   43   84.4619   342.214   344.013   -4015.15   0.161916   43   104   43   84.4597   342.209   344.029   -4015.1   5370.19   43   
10	1   0   1.16073   -2.99891   -46.351   5.01026   0.503952   0   1   0   1.16073   -2.99891   -46.351   5.01026   755933   0   

To track the electron charge produced through the ionization, the fragment itself should be fired on Ar-CO2 target, then we check the track. since unfortunately having the electrons simultaneously from the fission event needs more search (may be new programming for steppingVerbose to have a tracking Verbose 3 for the 2nd secondaries)

References

1-Claudio Tuniz, W. Kutschera, D. Fink, Gregory F. Herzog 2009,Accelerator Mass Spectrometry: Ultrasensitive Analysis for Global Science,Taylor and Francis p279.

2- Facina,M. 2004. A gas catcher for the selective production of radioactive beams through laser ionization,Heverlee, Master Thesis, Instituut voor Kern- en Stralingsfysica,211p. File:Thesis Facina ionization in Ar.pdf

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