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 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