Hello everyone,
I would like to ask how Geant4 simulates Total Reflection X-ray Fluorescence (TXRF). Is it sufficient to achieve this simulation by setting the material surface reflectivity?
I just want to know if Geant4 can simulate total reflection XRF. I tried using 8keV X-rays incident on a Fe metal surface at an angle of 0.1 degrees, but it seems that total reflection is not occurring.
I really need assistance.
Geant4 defines two different kinds of “photons,” which serve different purposes and have different processes associated with them. When simulating nuclear or atomic physics which produces gamma rays, X-rays, or even eV-scale “visible” transition lines, Geant4 uses the G4Gamma particle. This is the particle that participates in “EM physics,” Compton scattering, Thompson scattering, bremsstrahlung, etc.
For modeling the transport of visible light through transparent materials (like Cherenkov detectors, scintillators, etc.), Geant4 uses the G4OpticalPhoton particle. This particle only participates in reflection, refraction, and so on.
To model something like an X-ray telescope, with grazing incidence focusing, you would likely need to run two different simulations. First, run the simulation you want to generate X-rays, and record the position, energy and direction of each X-ray (G4Gamma) at some convenient reference plane. Then you need a second simulation, where you read back that data, and instantiate a G4OpticalPhoton for each entry. In the second geometry, make sure you define index of refraction, reflectivity, whatever for the optical physics processes at the appropriate energies.
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Thank you for your answer. It has been very helpful to me. I will go and consult the BookForApplicationDevelopers to learn how to use G4OpticalPhoton for simulation.