Least fission fragment K.E needed for ionization
Simulation Conditions and constraints
Detector Construction
The detector is designed based on example N03, a Ar/CO2 (90-10) layer absorber of thickness 10 cm, and has 1 atmospheric pressure and 300 K temperature.
Physics List
G4hIonization is the process under the generic ion, electrons are expected to scatter in all directions, only the Bremsstrahlung process is concerned.
Projectiles
From the mass distribution spectrum below, a peak exists for A=103 and another for A=83 for Th-232 fission reaction.
The same fragments are used as projectiles toward the absorber.
One of the element tested is O-17, the minimum energy to emit a tracked electron is 8 MeV, otherwise the table will mention hionization.
- O-17 with K.E = 7 MeV
*********************************************************************************************************
* G4Track Information: Particle = O17[0.0], Track ID = 1, Parent ID = 0
*********************************************************************************************************
Step# X Y Z KineE dEStep StepLeng TrakLeng Volume Process
0 -7.2 mm 0 fm 0 fm 7 MeV 0 eV 0 fm 0 fm World initStep
1 -6 mm 0 fm 0 fm 7 MeV4.25e-16 eV 1.2 mm 1.2 mm World Transportation
2 4 mm 0 fm 0 fm 7 MeV3.54e-15 eV 1 cm 1.12 cm Layer Transportation
3 4.09 mm 0 fm 0 fm 6.87 MeV 125 keV 89.4 um 1.13 cm ArCO2 hIoni
4 4.11 mm 0 fm 0 fm 6.85 MeV 22.1 keV 21.8 um 1.13 cm ArCO2 hIoni
5 4.14 mm 0 fm 0 fm 6.82 MeV 37.2 keV 29.3 um 1.13 cm ArCO2 hIoni
6 4.41 mm 0 fm 0 fm 6.4 MeV 413 keV 272 um 1.16 cm ArCO2 hIoni
7 4.59 mm 0 fm 0 fm 6.17 MeV 231 keV 174 um 1.18 cm ArCO2 hIoni
8 6.65 mm 0 fm 0 fm 2.8 MeV 3.38 MeV 2.06 mm 1.39 cm ArCO2 hIoni
9 8.29 mm 0 fm 0 fm 0 eV 2.8 MeV 1.64 mm 1.55 cm ArCO2 hIoni
---> End of event: 0
Absorber: total energy: 7 MeV total track length: 4.28725 mm
Gap: total energy: 0 eV total track length: 0 fm
Run terminated.
Run Summary
Number of events processed : 1
User=0s Real=0.09s Sys=0s
--------------------End of Run------------------------------
mean Energy in Absorber : 7 MeV +- 0 eV
mean Energy in Gap : 0 eV +- 0 eV
mean trackLength in Absorber : 4.28725 mm +- 0 fm
mean trackLength in Gap : 0 fm +- 0 fm
------------------------------------------------------------
- O-17 K.E = 8 MeV
*********************************************************************************************************
* G4Track Information: Particle = O17[0.0], Track ID = 1, Parent ID = 0
*********************************************************************************************************
Step# X Y Z KineE dEStep StepLeng TrakLeng Volume Process
0 -7.2 mm 0 fm 0 fm 8 MeV 0 eV 0 fm 0 fm World initStep
1 -6 mm 0 fm 0 fm 8 MeV4.04e-16 eV 1.2 mm 1.2 mm World Transportation
2 4 mm 0 fm 0 fm 8 MeV3.37e-15 eV 1 cm 1.12 cm Layer Transportation
3 4.13 mm 0 fm 0 fm 7.83 MeV 167 keV 129 um 1.13 cm ArCO2 hIoni
4 4.18 mm 0 fm 0 fm 7.76 MeV 69.4 keV 49.6 um 1.14 cm ArCO2 hIoni
:----- List of 2ndaries - #SpawnInStep= 1(Rest= 0,Along= 0,Post= 1), #SpawnTotal= 1 ---------------
: 4.18 mm 0 fm 0 fm 994 eV e-
:----------------------------------------------------------------- EndOf2ndaries Info ---------------
5 4.27 mm -4.39 Ang -2.73 Ang 7.66 MeV 100 keV 88.3 um 1.15 cm ArCO2 hIoni
6 4.32 mm -7.02 Ang -4.36 Ang 7.58 MeV 81.4 keV 52.8 um 1.15 cm ArCO2 hIoni
7 4.33 mm -7.78 Ang -4.84 Ang 7.56 MeV 20.8 keV 15.2 um 1.15 cm ArCO2 hIoni
8 4.39 mm -1.05 nm -6.53 Ang 7.49 MeV 65.4 keV 54.7 um 1.16 cm ArCO2 hIoni
9 4.74 mm -2.79 nm -1.74 nm 7 MeV 499 keV 350 um 1.19 cm ArCO2 hIoni
10 4.81 mm -3.14 nm -1.95 nm 6.88 MeV 113 keV 68.8 um 1.2 cm ArCO2 hIoni
11 5.14 mm -4.77 nm -2.97 nm 6.4 MeV 477 keV 329 um 1.23 cm ArCO2 hIoni
12 6.15 mm -9.79 nm -6.09 nm 4.95 MeV 1.45 MeV 1.01 mm 1.33 cm ArCO2 hIoni
13 8.06 mm -19.3 nm -12 nm 1.61 MeV 3.34 MeV 1.91 mm 1.53 cm ArCO2 hIoni
14 9.53 mm -26.7 nm -16.6 nm 0 eV 1.61 MeV 1.47 mm 1.67 cm ArCO2 hIoni
*********************************************************************************************************
* G4Track Information: Particle = e-, Track ID = 2, Parent ID = 1
*********************************************************************************************************
Step# X Y Z KineE dEStep StepLeng TrakLeng Volume Process
0 4.18 mm 0 fm 0 fm 994 eV 0 eV 0 fm 0 fm ArCO2 initStep
1 4.19 mm 1.12 um 694 nm 0 eV 994 eV 57.2 um 57.2 um ArCO2 eIoni
---> End of event: 0
Absorber: total energy: 8 MeV total track length: 5.59051 mm
Gap: total energy: 0 eV total track length: 0 fm
Run terminated.
Run Summary
Number of events processed : 1
User=0s Real=0.1s Sys=0s
--------------------End of Run------------------------------
mean Energy in Absorber : 8 MeV +- 0 eV
mean Energy in Gap : 0 eV +- 0 eV
mean trackLength in Absorber : 5.59051 mm +- 0 fm
mean trackLength in Gap : 0 fm +- 0 fm
------------------------------------------------------------
Results and Conclusions
Based on the observation for O-17, for every hionization process we may consider minimum an electron released with a certain can be calculated if GEANT4 does not track the electron.
GEANT4 does not track the electron interaction after the ionization process, so may take the information given about any free electron then fire it again to record the processes occur in the medium or study just one process as bremsstrahlung.
- Defination
The amount of energy expended in the gas per per ion pair produced will be represented by w. <ref name="Valentine">J.M. valentine, C.Curran, Reports on progress in phyiscs,21, 1 (1958) 1-29 </ref >
The energy needed to release a number of free electrons by ionization is basically depending on:<ref name="Valentine"/>
1- Gas nature.For apha particles of energy 6 MeV in a helium gas, w=41.1 eV for highly pure helium, w=30 eV for helium with impurities to a level of of one part in a thousand.
2- The Ionizing particle's energy and type.
For Ar gas, w-values (in eV) are listed according to the incident particle :
| 9 keV x-rays | 10 keV electrons | 40 keV electrons | x-rays Ar-37(K-capture)(5-25 keV) + beta | alpha 7.68 MeV | 340 MeV protons |
| 27.9 +_ 1.5 | 27.3 | 25.4 | 27.0 +_ 0.5 | 26.25 | 25.5 |
References
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