Spallation reactions

Spallation reactions are important in various fields of research such as astrophysics, neutron sources and production of radioactive beams. To get a quantitative understanding of the spallation mechanism and to improve its modeling, which is needed for accurate simulations of, e.g., sub-critical reactors coupled with high-intensity proton beams designed as radioactive waste burners, exclusive measurements of the reaction channels are mandatory. First experiments in this direction were performed [1] at GSI at the ALADIN/LAND facility with high-energy (1 GeV/nucleon) Fe beams impinging on a liquid hydrogen target. Such studies are most interesting to be extended to heavier systems, which is prohibited at present, however, due to experimental limitations. We intend to measure spallation with two heavy beams, ²⁰⁸Pb and ²³⁸U. The first one constitutes the main component of the spallation target in accelerator driven systems, while the second allows studying the role of fission in spallation reactions. The R³B facility provides the ideal setup for such studies making use of the large-acceptance dipole magnet with its large bending power. The goal will be to identify all the products in mass and nuclear charge (isotopic distributions) of the reactions and measure their velocities so that a complete reconstruction of the excited system at the end of the first stage of the reaction could be achieved. This would allow, for the first time for heavy projectiles, for a detailed study of the competition between the different de-excitation mechanisms (evaporation, fission, emission of intermediate-mass fragments, see also the sections on fission, projectile fragmentation).

[1] J.E. Ducret et al., SPALADIN experiment, performed at GSI, proposal S248.