The screened relativistic treatments for electrons, protons and ions [Geant4: Class G4IonCoulombScatteringModel (2014)], and only for Coulomb interaction, are included in Geant4 simulation code. Some tests were carried on to verify consistency of the latest version of Geant4 (10.1) with respect to the SR-NIEL analytical treatment.
Some bugs were spotted and corrected in the next patches that will be distributed in the coming months. The lastest version of the SR-NIEL classes is available in this website.
The following results are obtained with the patch already applied.
Protons in Silicon
The easiest geometry was used in these tests: Protons incident on a slice of Silicon. The numer of incident protons and the thickness of the slice were tuned to get enough statistic with resonable computing time.
Total Cross Section (Coulomb Interactions)
Total Cross section in Geant4 code and in SR-NIEL for Coulomb interactions were computed and compared for Protons incident on a Silicon target.
The mean difference is less than 0.1%.
Differential Cross Section (Coulomb Interactions)
107 Protons were generated for traversing a slice of silicon 10 Å thick and 3.8x105 interactions were produced. The thickness was kept as thin as possible to reduce the multiple scattering effects in the angle distribution Y(θ) and the energy loss of the trasmitted particles. The differential cross section was calculated as:
where Y(θ) is the number of particle deflected between θ and θ+dθ, n0 is number of incident particles, N the number density of silicon atoms, x the thickness of the target slice and ΔΩ the solid angle between θ and θ+dθ.
The calculated differential cross section was compared to the analytical one contained in SR-NIEL code for Coulomb interactions:
Nuclear Stopping Power (Coulomb Interactions)
Following is the results of Nuclear Stopping Power coming from simulations in Geant4 compared with the SR-NIEL results for Coulomb interactions. A variable number (to obtain ~105 displaced atoms) of protons were generated for traversing a slice of Silicon 1μm thick.
Non Ionizing Energy Loss (Coulomb Interactions)
Following is the results of the Non Ionizing Energy Loss (NIEL) coming from simulations in Geant4 compared with the SR-NIEL results for Coulomb interactions. A variable number (to obtain ~105 displaced atoms) of protons were generated for traversing a slice of Silicon 1μm thick. The threshold energy for displacement was set to 21 eV.
Geant4: Class G4IonCoulombScatteringModel~(2014).
Class Description: Single Scattering Model for protons, alpha and heavy Ions (Ref.~Boschini et al. 2011), Software Reference Manual
Source Code Version: Geant4 10.0 (December 2013) avaliable at the website
See also Sections~6.5--6.5.7 of Physics Reference Manual for version 10.0 available at the website: