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Subject: Modelling Gamma Rays

Question:

We are attempting to model the interactions of gamma rays using a monte carlo simulation as part of our 3rd year Astrophysics degree. Could you tell me the assumptions/equations you used in calculating the gamma ray interactions and the detection method used.

Answer:

Thanks for your question. Our GLAST [Fermi] simulation uses Geant4 for the underlying particle transport (see http://wwwinfo.cern.ch/asd/geant4/geant4.html). The electromagnetic interactions are handled by EGS4 (see http://www.slac.stanford.edu/egs/).

Dr. Steven Ritz, NASA-GSFC
Fermi Deputy Project Scientist and LAT Instrument Scientist