Maxime Louvel

Surveying the nuclear caloric curve

Abstract The 4π array INDRA was used to detect nearly all charged products emitted in Ar + Ni collisions between 52 and 95 MeV/u. The charge, mass and excitation energy E ∗ of the quasi-projectiles have been reconstructed event by event. Excitation energies up to 25 MeV per nucleon are reached. Apparent temperatures obtained from several double isotopic yield ratios Tr0 show different dependences upon E ∗ . T6Li7Li3Heα0 yields the highest values, as well as the high energy slopes Ts of the kinetic energy spectra. Two statistical models, sequential evaporation and gas in complete equilibrium, taking into account side feeding and discrete excited states population, show that the data can be explained by a steady increase of the initial temperature with excitation energy without evidence for a liquid-gas phase transition.

Disappearance of flow as a function of impact parameter and energy in nucleus-nucleus collisions☆

Abstract The dependence of collective nuclear flow on impact parameter and beam energy from 25 to 85 MeV/u has been measured for Ar+Al with the 4 π array Mur+Tonneau. The flow of the particles emitted from the interaction region falls to zero at a beam energy in the range 70–80 MeV/u for impact parameters below 2 fm. This energy increases with the impact parameter. This study as a function of the impact parameter and the energy should allow information both on the nucleon-nucleon crosss section in medium and the EOS of nuclear matter to be obtained.

IS REDUCIBILITY IN NUCLEAR MULTIFRAGMENTATION RELATED TO THERMAL SCALING

Abstract Thermal scaling (Arrhenius law for an “elementary” probability p of binomial function) and reducibility in intermediate mass fragments (IMFs) production are examined for data of the reaction 129Xe+ natSn at 50 MeV/u. The study of the longitudinal velocities and of the average transverse energies of the IMFs contradicts the assumption that the total transverse energy of all detected particles Et is related to a well defined temperature. The separation of Et into the total transverse energy of light charged particles (Z=1,2) and that of IMFs elucidates the algorithm which induces a linear behavior of log(1/p) versus 1/ E t . Even in the case of a single thermalized source, calculations based on a sequential statistical model show that the Arrhenius law cannot be observed if Et is taken as an estimation of the thermal energy.