SSNTD studies of lead nuclei fission induced by relativistic p, d, He and C-12 projectiles inside massive Pb and U targets

A series of experiments was carried out with relativistic protons, deuteron s, helium and carbon-12 projectiles accelerated at SYNCHOPHASOTRON LHE, Dub na which hit massive Pb and U targets. The beam profiles and intensities of both primary particles and secondary fast neutrons were measured using pla stic SSNTD inside the massive cylinder blocks of Cu, Pb and U by counting o f fission fragment tracks due to the induced fission of Pb nuclei. The beam diameter increases typically by 20-30 % at the depth 10 and 20 cm. With in creasing the energy of projectiles the number of secondary neutrons rises w ith the depth for protons, deuterons and helium ions. Nevertheless, for C-1 2 ions beams with changing the energy from 18 GeV to 44 GeV we first observ e the effect of significant increase both the yield of secondary fast neutr ons and the half-width of the beam. The observed enhanced yield of secondary fast neutrons confirms unusual beh avior of nuclear interaction cross section of 44 GeV C-12 ions observed ear lier in our studies with massive blocks of Cu, Pb and U.