Difference between revisions of "Alpha Ionization"

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=Alpha Particles ionization simulation using GEANT4=
 
=Alpha Particles ionization simulation using GEANT4=
  
GEANT4 simulates the ionization of alpha particles in Ar/CO2 90/10 gas. Geant4 can simulate the ionization process for alpha particles, but unfortunately the value of the step function that determines the number of delta electrons is very low even by decreasing the cut to 1 nm. Also the range of alpha particles in Ar/CO2 gas is not accurate and does not match  the projected ranges using srim [[File:Alpha_range_ArCo2.txt]], the following table  shows the maximum range of the alpha particles that are emitted from the U-233, and the ranges calculated by srim.
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GEANT4 simulates the ionization of alpha particles in Ar/CO2 90/10 gas. Geant4 can simulate the ionization process for alpha particles. Unfortunately the value of the step function underestimates the number of delta electrons. This is an issue even after decreasing the step cut to 1 nm. Also, using GEANT4 overestimates the range of alpha particles in Ar/CO2 gas when compared to those that srim calculates [[File:Alpha_range_ArCo2.txt]], the following table  shows the maximum range of alpha particles that are emitted from the U-233, and the ranges calculated by srim.
  
 
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Based on the previous table, GEANt4 failed to calculate the expected alpha range for most energy, in addition to underestimating the number of alpha's delta electrons emitted through that range.
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Based on the previous table, GEANT4 failed to calculate the expected alpha range for most alpha energies, and underestimated the number of alpha's delta electrons emitted through that range.
  
 
=Calculating the number of the delta electrons without using GEANT4=
 
=Calculating the number of the delta electrons without using GEANT4=

Revision as of 01:42, 4 February 2014

Alpha Particles ionization simulation using GEANT4

GEANT4 simulates the ionization of alpha particles in Ar/CO2 90/10 gas. Geant4 can simulate the ionization process for alpha particles. Unfortunately the value of the step function underestimates the number of delta electrons. This is an issue even after decreasing the step cut to 1 nm. Also, using GEANT4 overestimates the range of alpha particles in Ar/CO2 gas when compared to those that srim calculates File:Alpha range ArCo2.txt, the following table shows the maximum range of alpha particles that are emitted from the U-233, and the ranges calculated by srim.

Alpha Energy (MeV) G4 Range (cm) Srim Range (um)
1.0 0.56599 129.49
2.0 1.1467 255.91
3.0 1.9024 417.27
4.0 2.8012 612.45
5.0 3.8425 839.91

Based on the previous table, GEANT4 failed to calculate the expected alpha range for most alpha energies, and underestimated the number of alpha's delta electrons emitted through that range.

Calculating the number of the delta electrons without using GEANT4

there is Another way to Calculate the number of delta electrons without using GEANT4. It starts by calculating the average energy loss [math] \Delta E_a[/math] by the alpha and average energy loss per unit length [math] {\zeta} [/math] in Ar/CO2 gas using Bethe-Block equation,then using the the following equation:

[math] \lambda = \frac{ \Delta E - \Delta E_a}{\zeta} [/math]

to calculate the actual energy loss by ionization [math] \Delta E [/math], where [math] \lambda [/math] represents random landau number. By dividing the energy loss by the minimum energy for producing a pair of ion/electron W, it gives the number of electrons emitted by ionization.

Srim can simulate the motion of an alpha particle in Ar/CO2 gas by considering the change in the stopping power per unit length, it can also show the ionization energy loss as shown in the following figure:

4.8MeV ionization ArCo2.jpeg

The figure shows the ionization energy loss of 999 alpha particles as they pass through a 0.85 mm Ar/CO2 gas. integrating the area under the curve, then dividing by (W*1000) will give the number of delta electrons produced by an alpha particle.