Physical rigour is maximised by employing the available cross sections and sampling distributions and the most complete physical model for describing the transport and production of the photon/electron/positron cascade from 20.0 MeV down to 1.0 kev. FOTELP/EM is developed for photon, electron and positron numerical experiments by Monte Carlo for dosimetry, radiation damage, radiation therapy and other applications.
For photon history the trajectory is generated by following it from scattering to scattering using corresponding inverse distribution between collision, types of target, types of collisions, types of secondaries, their energy and scattering angles. Photon interactions are: photoelectric absorption, incoherent scattering, pair production, and coherent scattering. The secondary photons which are followed include bremsstrahlung and positron-electron annihilation radiation.
The condensed history Monte Carlo method (Berger 1963) is used for the electron and positron transport simulation. During a history the particles lose energy in collisions, and the secondary particles are generated on the step according to the probabilities of their occurrence. Electron (positron) energy loss is through inelastic electron-electron (e-,e-) and positron-electron (e+,e-) collisions and bremsstrahlung generation. The fluctuation of energy loss (straggling) is included according to the Landau's or Blunk-Westphal distributions with 9 gaussians. The secondary electrons which follow history of particles include knock-on, pair Compton and photoelectric electrons. The secondary positrons which follow pair production are included, too. With atomic data, the electron and positron Monte Carlo simulation is broadened to treat atomic ion relaxation after photoeffect and impact ionization. In the presence of electric and/or magnetic fields, FOTELP/EM estimates trajectory of charge particles on the step in the actual zone. Flexibility of the codespermits them to be tailored to specific applications and allows the capabilities of the codes to be extended to more complex applications.