Modeling and optimization of electron linac exit systems for nuclear technologies

The possibility of producing linac-based high-intensity sources of high-energy bremsstrahlung ( > 10 15 photons / cm 2 s ) and photoneutrons (up to 10 14 neutrons / cm 2 s ) holds much promise for the use of these sources in various branches of applied nuclear physics (medical isotope production, transmutation studies of nuclear-cycle long-lived by-products, testing materials for long-term immobilization of radioactive waste, etc.). An accelerator with an energy of ⩾ 30 MeV , beam power of > 10 kW and the highest possible beam-current density appears appropriate for the generation of secondary radiation with the required parameters. However, the electron beam handling presents some thermophysical problems on account of high power absorption in the accelerator exit window, the bremsstrahlung converter and the target. Therefore, each of the technologies mentioned demands optimization of both the geometry and design of the exit systems and the accelerator beam parameters. This report offers some solutions to the problems mentioned by means of computer simulation based on GEANT and PENELOPE systems. The codes developed are supplemented with data on excitation functions of the corresponding photonuclear reactions.