Radiation field characterization and shielding studies

The achieved performances in terms of energy and brightness of laser-accelerated particle beams require a proper shielding assessment for the primary and secondary ionizing radiation, especially when high intensity laser systems operate in repetition rate (typically in the range 0.1-10 Hz). In the frame of the ELI Beamlines project a general shielding study for both the 10 PW (0.016 Hz) and 2 PW (10 Hz) laser beamlines, dedicated to the high energy electron and proton acceleration, has been performed. All the work has been done keeping in mind that we deal with a rapidly evolving field, where not all the parameters that characterize the radiation fields can be completely set at this stage: the precise description of the source particle distributions, double-differential in energy and in angle, can evolve with the improved knowledge, and on the other hand the workload (in terms of shots/day), could be optimized in the future with the increased experience and technological improvements. The general philosophy has been therefore to maintain a realistic approach, always conservative, and adopt where possible flexible solutions. In the present work a summary of the analysis done and the solutions proposed for the longitudinal containment of the radiation in the proton acceleration experimental area is illustrated and discussed.