arXiv subjects

G. Tabacaru

Publications and source records attributed to G. Tabacaru.

25 records · Page 2Linked to original sources

arXiv2001

Liquid-Gas Coexistence Region in Central Xe+Sn Reactions

Charge partitions and distributions of fragments emitted in multifragmentation of fused systems produced in central collisions are studied over the incident energy range 32-50 MeV per nucleon. Most of the charged products are well identified thanks to the high performances of the INDRA 4pi array. Supported by dynamical calculations, charge correlations are used t$ evidence, or not, spinodal instabilities and consequently the liquid-gas coexistence region over the considered incident energy range. It was claimed in the last few years that mass/charge distributions should follow a power law behavior in the coexistence region. The Z distributions measured are discussed. A first attempt is made to derive in which Z region the border between liquid and gas parts is located.

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arXiv2001

Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions (Part I): recombination and delta -- electrons

A simple formalism describing the light response of CsI(Tl) to heavy ions, which quantifies the luminescence and the quenching in terms of the competition between radiative transitions following the carrier trapping at the Tl activator sites and the electron-hole recombination, is proposed. The effect of the delta rays on the scintillation efficiency is for the first time quantitatively included in a fully consistent way. The light output expression depends on four parameters determined by a procedure of global fit to experimental data.

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arXiv2001

Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions (Part II): calibration and identification in the INDRA array

The light output of the 324 CsI(Tl) scintillators of INDRA has been measured over a large range both in energy: 1 - 80 AMeV and in atomic number of incident ions: Z = 1 - 60. An analytical expression for the nonlinear total light response as a function of the energy and the identity of the ion is proposed. It depends on four parameters. For three of them, connected to CsI(Tl) intrinsic characteristics, recommended fixed values are proposed. They are issued from the comparative study of the forward scintillators of INDRA, based on intermediate mass fragment data. The fourth one, related to light collection and to the gain of the associated photomultiplier, is particular and may be accurately obtained afterwards, from light charged particle data. Two applications are presented: fragment identification in telescopes using a CsI(Tl) crystal as residual energy detector and the scintillator energy calibration. The results are successfully confronted to heavy fragment experimental data.

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arXiv2001

Evidence for Spinodal Decomposition in Nuclear Multifragmentation

Multifragmentation of a ``fused system'' was observed for central collisions between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products were well identified thanks to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but non ambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a ``fossil'' signal of spinodal instabilities in finite nuclear systems.

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arXiv2001

Experimental evidence for spinodal decomposition in multifragmentation of heavy systems

Multifragmentation of fused systems was observed for central collisions between 32 AMeV 129Xe and Sn, and 36 AMeV 155Gd and U. Previous extensive comparisons between the two systems led to the hypothesis of spinodal decomposition of finite systems as the origin of multifragmentation for incident energies around 30 AMeV. New results on velocity and charge correlations of fragments bring strong arguments in favor of this interpretation.

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arXiv2000

Effect of the intermediate velocity emissions on the quasi-projectile properties for the Ar+Ni system at 95 A.MeV

The quasi-projectile (QP) properties are investigated in the Ar+Ni collisions at 95 A.MeV taking into account the intermediate velocity emission. Indeed, in this reaction, between 52 and 95 A.MeV bombarding energies, the number of particles emitted in the intermediate velocity region is related to the overlap volume between projectile and target. Mean transverse energies of these particles are found particularly high. In this context, the mass of the QP decreases linearly with the impact parameter from peripheral to central collisions whereas its excitation energy increases up to 8 A.MeV. These results are compared to previous analyses assuming a pure binary scenario.

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arXiv2000

Multifragmentation of a very heavy nuclear system (II): bulk properties and spinodal decomposition

The properties of fragments and light charged particles emitted in multifragmentation of single sources formed in central 36AMeV Gd+U collisions are reviewed. Most of the products are isotropically distributed in the reaction c.m. Fragment kinetic energies reveal the onset of radial collective energy. A bulk effect is experimentally evidenced from the similarity of the charge distribution with that from the lighter 32AMeV Xe+Sn system. Spinodal decomposition of finite nuclear matter exhibits the same property in simulated central collisions for the two systems, and appears therefore as a possible mechanism at the origin of multifragmentation in this incident energy domain.

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