I am unable to understand the following Geant4 output:
I implemented in both MCNP and Geant4 a pencil beam electron source of 150 keV that hit a tungsten target to produce electromagnetic radiation.
In MCNP, I scored the photons spectrum using F4 tally card (by creating a cell box and placing it in front of the tube’s opening) while in Geant4 I adopted command based scoring, creating a Probe (of the same size as the box in MCNP) and scored volumeFlux for gamma inside it, also placed in front of the tube’s opening.
In Geant4, I activated deexcitationIgnoreCut, Fluo, PIXE, Auger and AugerCascade and the PhysicsList class used was G4EmStandardPhysics_opt4.
My problem is that I obtain two different spectra, in Geant4 one can see that the continuous electromagnetic radiation is smaller than the one from MCNP.
Can someone explain to me why the continuous em radiation is smaller in Geant4, am I omitting to activate some physical processes?
Thank you in advance.
Below are the spectra and the X-ray tube I simulated: