Accueil > Thèmes de recherche

The research program of the INDRA collaboration is mainly focused on the dynamics of nucleus-nucleus collisions at low and intermediate energies and on the thermodynamics of warm and hot nuclei produced in those collisions.

The central topics are the nuclear energy density functional, the de-excitation properties of nuclei and the phase transition of hot nuclei. For each topic, studies with the introduction of the N/Z degree of freedom are in progress. Constraints on the different functionals produced by theory are brought by

experimental data on collision dynamics. De-excitation properties concern compound nuclei, multifragmentation and vaporization of nuclei. The phase transition of hot nuclei early related to multifragmentation is studied in the context of first-order phase transitions in non-extensive systems and so nucleus-nucleus collisions are a unique laboratory of statistical mechanics of finite systems.

In the last decade scientific achievements of the INDRA collaboration were the following :

**collision dynamics :** mid-rapidity emission, aligned fission, stopping, directed

and elliptic flow, pre-equilibrium emission, isospin diffusion,

**vaporization of hot nuclei :** identification of a real gas of fermions and

bosons in thermal and chemical equilibrium,

**multifragmentation of hot nuclei :** fragment excitation energy limitation

around 3.0-3.5 MeV/nucleon, determination of freeze-out properties,

entrance channel effects – expansion energy, freeze-out volumes, partitions,

**scalings and order parameter of a phase transition :** delta scaling of the

heaviest fragment (order parameter), Fisher scaling,

**signals of a 1st order phase transition in finite non-extensive systems :**

dynamics of the transition (spinodal fluctuations), negative heat capacity,

bimodality of the size distribution of the heaviest fragment, extraction

of the coexistence zone of the transition, first estimate of the associated

latent heat,

**multiparticle correlation functions :** structure of light nuclei,

**detection physics :** interaction of heavy ions with silicon detectors and CsI(Tl) scintillators.

For the near future the main priorities can be summarized as follows :

**collision dynamics :** constraints on the symmetry term of the energy density

functional (density and temperature dependence) brought by pre-equilibrium,

mid-rapidity emission, stopping, isospin diffusion,

**compound nuclei de-excitation :** influence of neutron enrichment on the

decay mechanism and on the level density parameters,

**multifragmentation of hot nuclei :** evolution of properties with N/Z of

fragmenting nuclei, N/Z contents of fragments (surface and volume

terms of symmetry energy)

**scaling and order parameter of a phase transition :** delta scaling of the

heaviest fragment (order parameter),

**signals of a 1st order phase transition in finite non-extensive systems :**

dynamics of the transition in relation with the introduction of the N/Z degree

of freedom, neutron enrichment of the gas phase.

To achieve such studies, an expanding range of exotic beams becomes available. Moreover the multidetector INDRA will be used in conjunction with FAZIA modules, providing isotopic determination for fragments, and with other devices such as spectrometers or neutron detectors.