The use of Monte Carlo radiation transport codes in radiation physics and dosimetry

Transport and interaction of electromagnetic radiation Interaction models and simulation schemes implemented in modern Monte Carlo codes for the simulation of coupled electron-photon transport will be briefly reviewed. In these codes, photon transport is simulated by using the detailed scheme, i.e., interaction by interaction. Detailed simulation is easy to implement, and the reliability of the results is only limited by the accuracy of the adopted cross sections. Simulations of electron and positron transport are more difficult, because these particles undergo a large number of interactions in the course of their slowing down. Different schemes for simulating electron transport will be discussed. Condensed algorithms, which rely on multiple-scattering theories, are comparatively fast, but less accurate than mixed algorithms, in which hard interactions (with energy loss or angular deflection larger than certain cut-off values) are simulated individually. The reliability, and limitations, of electron-interaction models and multiple-scattering theories will be analyzed. Benchmark comparisons of simulation results and experimental data will also be presented, together with examples from applications in radiotherapy, detector response studies and microanalysis. Transport and interaction of hadronic radiation The physical bases for the description of medium and high energy hadron transport and interactions in Monte Carlo codes will be briefly reviewed. Atomic processes (dE/dx, multiple Coulomb scattering, etc) will not be discussed in details, because of their similarities with those of electron and positrons (discussed in the second lecture). The lecture will mostly concentrate on modelling of hadron nuclear interactions. The various steps customarily used in describing nuclear interactions 1) Hadron-nucleon interactions 2) Glauber-Gribov cascade 3) (Generalized) IntraNuclear cascade 4) Preequilibrium 5) Evaporation/fission/fragmentation 6) Gamma deexcitation will be introduced and discussed mainly focusing on their relative role in determining final state properties of relevance for radiation protection and dosimetry. Examples from real life codes and comparisons with experimental data will be also presented. Application of Monte Carlo codes in radiation shielding and dosimetry This lecture will review some of the applications of Monte Carlo codes in radiation physics and dosimetry, providing a number of examples with comparison with experimental results where available. The following topics will be addressed: 1) calculation of radiation shielding and energy deposition studies for the LHC and for future CERN high-power accelerators; 2) induced radioactivity in accelerators, its impact on accelerator operation and on accelerator decommissioning (the example of LEP); 3) exposure of man at commercial flight altitudes, modelling of aircraft to assess influence of material distribution around passengers and crew, and modelling the cosmic neutron field on earth; 4) example of designing radiation protection instrumentation; 5) calculations of fluence to dose conversion coefficients used to estimate the radiation risk to humans; 6) evaluation of radiation risk caused by exposure to narrow beams at high-energy accelerators (gas bremsstrahlung and high-energy protons).