Development of Theoretical Models and Numerical Calculations of Primary Radiation Damage Production in Irradiated Graphite Collimator Materials for LHC by Protons with the Energy 450 GeV

A theoretical model is developed for the investigations and numerical calculations of primary radiation-induced point defect production in graphite collimator material for LHC due to formation of secondary fast particles in different nuclear reaction channels during irradiation of this material with the 450 GeV protons. On the basis of calculated elastic and inelastic scattering cross sections of neutrons on carbon atoms from the database ENDF-VII (neutron energies up to 150 MeV) and the data obtained using FLUKA, (neutron energy over 150 MeV) the numerical calculations of generation rates for primary point radiation defects are made due to formation of secondary fast neutrons. It is shown that the greatest generation rate of point radiation defects in graphite materials is determined by secondary pions with the generation rate of point defect formation an order of magnitude higher than the production rates of point defects due to secondary fast neutrons and other fast secondary particles. So the generation rate of primary point radiation defects in the interaction of pions and electrons with graphite collimator materials of LHC are comparable in order of magnitude (0.004 dpa/s per bunch) for each type of secondary particles. The contribution of secondary electrons and pions in the generation rate of primary point radiation defect formation is higher comparing with the contribution of secondary neutrons and protons and this val ue is varied from 5 to 10 times on average. Corresponding values in the generation rate of formation of primary point radiation defects for secondary neutrons and protons are not exceeding the value of 0.001 dpa/s per bunch for 450 GeV proton beam.