Alpha Ionization

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 the alpha particles, but unfortunately the value of the step function of the step function that determines the number of delta electrons is very low even by decreasing the cut to 1 nm. Also 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.

Alpha Energy (MeV)	G4 Range (cm)	Srim Range (um)
1	0.566	129.49
2	1.147	255.91
3	1.902	417.27
4	2.801	612.45
5	3.843	839.91

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.