L. Lebreton

Emission time scale of light particles in the system Xe+Sn at 50 AMeV. A probe for dynamical emission?

Abstract: Proton and deuteron correlation functions have been investigated with both impact parameter and emission source selections. The correlations of the system 129Xe+NatSn at 50 AMeV have been measured with the 4π INDRA which provides a complete kinematical description of each event. The emission time scale analyzed with a quantum model reveals the time sequence of the light particles emitted by the projectile-like fragment. The short and constant emission time of the proton, independent of the impact parameter, can be attributed to a preequilibrium process.

Gas chambers for identification of charged particles in 4π systems

Abstract Gas ionization chambers of a special shape adapted for 4π detector systems are presented. Different anode wire configurations are discussed for three working gases: Ar + methane(10%), isobutane, and tetrafluoromethane.

Evolution of Fragment Distributions and Reaction Mechanisms for the Ar+Ni System from 32 to 95 A.MeV

Within the framework of flow and multifragmentation study, the 36Ar+58Ni experiment has been performed at seven incident energies from 32 to 95 A.MeV with the INDRA detector at GANIL. After a brief description of the experimental set-up, the main trends as well as the evolution of fragment distributions will be presented. Some results about reaction mechanisms for particular classes of events will conclude this report.

Origin of complex fragments from32S+natAg reaction at 37.5 A·MeV

Fragment emission from collisions of32S withnatAg at 37.5 A·MeV has been studied with the 4π multi-detector AMPHORA. Production of intermediate mass and heavy fragments as well as of light charged particles has been measured. The total charged particle multiplicity and polar angular distributions have been used to select various classes of collisions. Analysis of angular and energy distributions of fragments and light particles in central collisions indicates the formation of a hot source (excitation energy of≈4.4 A·MeV) with an additional contribution from a preequilibrium process at more forward angles. Azimuthal angle correlations of He-Li, Li-Li, B-B, and C-C pairs have been used as a tool to study the origin of complex fragments. Data at backward angles are well described by considering a thermalized emitter with an angular momentum around 70ℏ and a fragment emission time of the order of 200 fm/c. A microscopic approach of BNV type confirms these emission times and angular momenta indicating the persistence of an incomplete fusion process responsible for the emission of complex fragments at backward angles.