Benoit Lott

Dynamical production of intermediate-mass fragments in peripheral 209Bi+136Xe collisions at ElabA=28 MeV

Abstract Intermediate-mass fragments (IMF) from the reaction 209 Bi+ 136 Xe at E lab A =28 MeV have been measured in coincidence with other charged reaction products, as well as with neutrons. The IMF emission patterns are seen to exhibit signatures of two mechanisms — statistical emission from the fully accelerated massive reaction partners and a fast dynamical emission from a single effective source. The latter mechanism, possibly involving a multiple neck rupture, becomes dominating for least dissipative collisions characterized by low associated light particle multiplicities.

A simple pulse processing concept for a low-cost pulse-shape-based particle identification

Abstract A simple method of pulse processing is described, which allows one to achieve at a very low cost a high-quality pulse-shape discrimination, using two commonly gated current-integrating ADCs. Results of application tests for a liquid NE213 scintillator detector (neutron-γ discrimination), as well as for a CsI(Tl) detector (p, d, t, α discrimination) are presented.

Light Particle Production in Spallation Reactions Induced by Protons of 0.8-2.5 GeV Incident Kinetic Energy

Absolute production cross sections have been measured simultaneously for neutrons and light charged particles in 0.8-2.5 GeV proton induced spallation reactions for a series of target nuclei from aluminum up to uranium. The high detection efficiency both for neutral and charged evaporative particles provides an event-wise access to the amount of projectile energy dissipated into nuclear excitation. Various intra nuclear cascade plus evaporation models have been confronted with the experimental data showing large discrepancies for hydrogen and helium production.

From Dissipative Collisions to Multiple Fragment Production — A Unified View

Over the last decade, much of the effort in intermediate-energy heavy-ion reaction studies has been focused on multifragmentation, [1, 2, 3, 4] a phenomenon leading to multiple intermediate-mass fragments (IMF) in the reaction exit channel. Since the standard statistical model appeared to be unable to account for the large observed IMF multiplicities, various models and scenarios have been proposed [5, 6, 7], which favor copious production of IMFs. On the other hand, in several recent studies [8, 9, 10], it was found that even in the Fermi energy domain, the binary dissipative collision scenario, well established at lower bombarding energies,[11] still accounts for most of the reaction cross section. The present paper shows that, like dissipative collisions, multiple-IMF emission is a dynamical process, driven by the kinetic energy of relative motion of projectile- and target-like fragments. A new, more complete, intermediate-energy heavy-ion reaction scenario is proposed that connects in a natural way the domains of dissipative collisions and multiple IMF production.