An activation database for materials used at high-intensity laser acceleration facilities

The ELI-Beamlines facility, which is expected to start operation in 2017, will be the high-energy, high repetition-rate laser pillar of the Extreme Light Infrastructure (ELI). The goal of the project is to deliver ultra-short, high-energy laser pulses for generation and applications of high-brightness X-ray sources and accelerated particles. Particle beams are expected to operate in an unprecedented energy range for laser-driven accelerators, going from 1 GeV up to 50 GeV for electrons and from 100 MeV up to 3 GeV for protons. The number of particles per laser shot is estimated to be 10^9-10^10 for electron beams and 10^10-10^12 for proton beams. The high energy and the large current per shot of the produced beams, together with the potentiality to operate at 10 Hz laser repetition rate, require an adequate evaluation of activation in structural materials in order to assess several radiation protection problems, such as minimization of residual dose rates close to and inside the experimental chambers and management of active materials (short and long-term storage and eventual decommissioning).
A large database covering all the energies and materials of interest is being developed using FLUKA, a Monte Carlo code successfully benchmarked for the production of radioactive nuclides. Results for electrons and protons at intermediate energies are presented. These results, although focused on the needs of laser-driven accelerators, are likely to be useful also when designing more conventional facilities.