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
Tr
0 show different dependences upon
E
∗
.
T
6
Li
7
Li
3
Heα
0 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.
Reaction mechanisms have been studied for two nearly symmetrical systems of different total mass, between 25 and 74
A
MeV. It is shown that collisions are mostly binary whatever the system mass and ...the bombarding energy. From the slowing-down of the partners, it is possible to establish the continuous evolution from quasielastic to (completely) damped collisions. It turns out that results are independent of the total system mass if involved energies are expressed in
A
MeV. The occurrence of mid-rapidity emission is also considered and may be used to establish a link between mechanisms observed at low and high bombarding energy. Part of it corresponds to a fast decay of outgoing partners.
The pulse-height defect (PHD) of
36Ar,
58Ni,
129Xe,
181Ta and
197Au ions in the 180 passivated ion-implanted silicon detectors of the INDRA array has been measured. The detectors faced the target ...with the low electric field side. The charge encoding ensured a low ballistic deficit. Detectors with the same nominal characteristics and electric field strength show a PHD dependence on the individual silicon wafer. They are classified and calibrated by using an empirical parametrization which relates the PHD to the total energy through a
Z-depending power law. A PHD analytical formula, based on a simple recombination model, is also proposed. It considers a realistic charge density variation with the position coordinate on the ion path. This new formula is successfully confronted to some experimental data.
Vaporization events detected with the 4π array INDRA, where all species have atomic numbers lower than 3 are studied. Binary dissipative collisions are found to be the dominant mechanism responsible ...for the production of such events. Due to large fluctuations (energy damping and mass of partners), the excitation energy of the vaporizing partners covers a very broad range from 6 to 28
AMeV.
Kinematical properties and chemical composition of vaporizing sources observed in heavy-ion collisions are presented. Vaporizing sources detected with the 4π array INDRA, are defined as sources for ...which all detected species have atomic numbers lower than 3. The excitation energy of the sources covers a very broad range (6–28
AMeV). The occurrence of thermodynamical equilibrium is discussed by comparing the data with the results of two statistical models. The model describing a gas in thermal and chemical equilibrium reproduces rather well the data suggesting that thermodynamical equilibrium may have been reached for such sources.
The INDRA multidetector has been used to study multifragmentation processes in central collisions for the Xe + Sn reaction at 50
A MeV. A single isotropic source formed at an excitation energy of 12
...A MeV exhausting most of the emitted charged products has been isolated in such collisions. The fragment kinetic energy spectra indicate a fast disintegration of the system with a radial collective motion of about 2
A MeV. The light charged particle characteristics within this scenario are also discussed.
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.
Using the 4π multidetector INDRA, collisions between
36Ar and
58Ni have been investigated over a broad bombarding energy range, from 32 to 95 AMeV. The onset for complete vaporization of the system ...into neutrons, H and He isotopes as well as the evolution with energy of the isotopic composition of the vaporization events were determined. Initial excitation energy needed for vaporization is discussed.
The new 4π multidetector INDRA, designed for the study of hot nuclear systems decaying by multifragmentation, is available for experiments since the beginning of 1993. First results emphasize its ...very high detection capabilities. Preliminary results on multiplicity distributions and elemental charge distributions in the most violent collisions for the
36Ar+
58Ni and
129Xe+
natSn systems are presented.
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