The role of collective radial expansion in determining multifragmentation partition properties ha... more The role of collective radial expansion in determining multifragmentation partition properties has previously been explored by comparing different-sized sources of the same excitation energy per nucleon formed by very different reaction mechanisms: excited quasi-projectiles from semi-peripheral Au+Au collisions and quasi-fused sources from central Xe+Sn collisions. New data has been obtained with INDRA on 181 Ta+ 66 Zn collisions in order to allow comparison of Xe+Sn data with quasi-fused systems having the same mass, charge and excitation energy per nucleon formed in mass-asymmetric reactions, for which a smaller initial compression is expected. Preliminary results confirm that, ceteris paribus, smaller radial flow leads to less fragments with more asymmetric partitions.
Experimental investigation of the sub-barrier fusion of neutron-rich light nuclei is important in... more Experimental investigation of the sub-barrier fusion of neutron-rich light nuclei is important in understanding the crusts of neutron stars, the structure of neutron-rich nuclei, and fusion dynamics of neutron-rich nuclei. It has recently been proposed that X-ray superbursts may originate from carbon burning ignited by heat from the fusion of neutron-rich oxygen nuclei in the crusts of accreting neutron stars
A study of identification properties of a Si-Si ΔE-E telescope exploiting an underdepleted residu... more A study of identification properties of a Si-Si ΔE-E telescope exploiting an underdepleted residual-energy detector has been performed. Five different bias voltages have been used, one corresponding to full depletion, the others associated with a depleted layer ranging from 90% to 60% of the detector thickness. Fragment identification has been performed using either the ΔE-E technique or the Pulse Shape Analysis (PSA). Both detectors are reverse mounted: particles enter from the low field side, to enhance the PSA performance. The achieved charge and mass resolution has been quantitatively expressed using a Figure of Merit (FoM). Charge collection efficiency has been evaluated and the possibility of energy calibration corrections has been considered. We find that the ΔE-E performance is not affected by incomplete depletion even when only 60% of the wafer is depleted. Isotopic separation capability improves at lower bias voltages with respect to full depletion, though charge identification thresholds are higher than at full depletion. Good isotopic identification via PSA has been obtained from a partially depleted detector, whose doping uniformity is not good enough for isotopic identification at full depletion.
Within the framework of flow and multifragmentation study, the 36 Ar+ 58 Ni experiment has been p... more Within the framework of flow and multifragmentation study, the 36 Ar+ 58 Ni 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 setup , 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.
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licenc... more Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Nuclear Physics at Border Lines - Proceedings of the International Conference, 2002
Heavy ion collisions at intermediate energies offer the possibility to investigate the role of th... more Heavy ion collisions at intermediate energies offer the possibility to investigate the role of the isospin degree of freedom in determining the evolution of the reaction mechanism in an energy domain dominated by the competition between one body and two body nuclear dynamics. The REVERSE experiment has been carried on the period September 1999 - May 2000, at the Laboratory
De-excitation modes of compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40... more De-excitation modes of compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40 Ca and 86 Kr+ 48 Ca collisions at 10 A.MeV, are investigated. In particular, the competition between the various disintegration decay paths of medium mass compound nuclei, formed by fusion processes and the isospin (related to N/Z) of the entrance channel influence on the decay process, are studied. Data were taken at the INFN-Laboratori Nazionali del Sud (LNS) in ISODEC experiment, by using the CHIMERA array. The experiment complements and improves the previous experiment performed at GANIL where the same mechanisms were studied at lower excitation energies. The results show the presence of a relaxed component in the reaction mechanism, evident staggering effects in the Z distributions, as well as different isotopic composition and neutron enrichment for the reaction products in the two systems.
The skin nucleus 8 He is investigated by measuring the angular distribution of the elasticly scat... more The skin nucleus 8 He is investigated by measuring the angular distribution of the elasticly scattered 8 He and the 6,4 He fragments produced in the collision with a 208 Pb target at 22 MeV, just above the Coulomb barrier. The experiment was carried out at SPIRAL/GANIL in 2010. Here we present preliminary results for the elastic scattering.
Cross sections, kinetic energy and angular distributions of fragments with charge 6 ≤ Z ≤ 28 emit... more Cross sections, kinetic energy and angular distributions of fragments with charge 6 ≤ Z ≤ 28 emitted in 78,82 Kr +40 C at 5.5 MeV/A reactions were measured at the GANIL facility using the INDRA apparatus. This experiment aims to investigate the influence of the neutron enrichment on the decay mechanism of excited nuclei. Data are discussed in comparison with predictions of transition state and Hauser-Feshbach models.
For nuclear reactions in which super-heavy nuclei can be formed, the essential difference between... more For nuclear reactions in which super-heavy nuclei can be formed, the essential difference between the fusion process followed by fission and non-equilibrium processes leading to fissionlike fragments is the reaction time. Quite probable non-equilibrium processes, characterized by very short reaction times, are highlighted thanks to mass-angle correlations. However, long lifetime components associated with fission following fusion have been observed with two independent experimental techniques, providing evidence for the formation of compound nuclei with Z = 120 and 124, followed by mass asymmetric fission.
Physics of Unstable Nuclei - Proceedings of the International Symposium on the ISPUN07, 2008
By contrast to composite systems with Z = 120 and Z = 124, no evidence for long lifetime componen... more By contrast to composite systems with Z = 120 and Z = 124, no evidence for long lifetime components could be found for composite systems with Z = 114 formed in the reaction 208Pb + Ge at 6.16 MeV/u.
Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of ¹... more Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of ¹²Xe projectiles with ¹¹²Sn nuclei at E/A=50 MeV is examined. Charge correlations reveal that symmetric breakups occur with significant probability. By selecting on the parallel velocity of the heaviest fragment we minimize the entrance channel dynamics. Calculations with the statistical decay code GEMINI failed to reproduce the experimental
The role of collective radial expansion in determining multifragmentation partition properties ha... more The role of collective radial expansion in determining multifragmentation partition properties has previously been explored by comparing different-sized sources of the same excitation energy per nucleon formed by very different reaction mechanisms: excited quasi-projectiles from semi-peripheral Au+Au collisions and quasi-fused sources from central Xe+Sn collisions. New data has been obtained with INDRA on 181 Ta+ 66 Zn collisions in order to allow comparison of Xe+Sn data with quasi-fused systems having the same mass, charge and excitation energy per nucleon formed in mass-asymmetric reactions, for which a smaller initial compression is expected. Preliminary results confirm that, ceteris paribus, smaller radial flow leads to less fragments with more asymmetric partitions.
Experimental investigation of the sub-barrier fusion of neutron-rich light nuclei is important in... more Experimental investigation of the sub-barrier fusion of neutron-rich light nuclei is important in understanding the crusts of neutron stars, the structure of neutron-rich nuclei, and fusion dynamics of neutron-rich nuclei. It has recently been proposed that X-ray superbursts may originate from carbon burning ignited by heat from the fusion of neutron-rich oxygen nuclei in the crusts of accreting neutron stars
A study of identification properties of a Si-Si ΔE-E telescope exploiting an underdepleted residu... more A study of identification properties of a Si-Si ΔE-E telescope exploiting an underdepleted residual-energy detector has been performed. Five different bias voltages have been used, one corresponding to full depletion, the others associated with a depleted layer ranging from 90% to 60% of the detector thickness. Fragment identification has been performed using either the ΔE-E technique or the Pulse Shape Analysis (PSA). Both detectors are reverse mounted: particles enter from the low field side, to enhance the PSA performance. The achieved charge and mass resolution has been quantitatively expressed using a Figure of Merit (FoM). Charge collection efficiency has been evaluated and the possibility of energy calibration corrections has been considered. We find that the ΔE-E performance is not affected by incomplete depletion even when only 60% of the wafer is depleted. Isotopic separation capability improves at lower bias voltages with respect to full depletion, though charge identification thresholds are higher than at full depletion. Good isotopic identification via PSA has been obtained from a partially depleted detector, whose doping uniformity is not good enough for isotopic identification at full depletion.
Within the framework of flow and multifragmentation study, the 36 Ar+ 58 Ni experiment has been p... more Within the framework of flow and multifragmentation study, the 36 Ar+ 58 Ni 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 setup , 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.
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licenc... more Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Nuclear Physics at Border Lines - Proceedings of the International Conference, 2002
Heavy ion collisions at intermediate energies offer the possibility to investigate the role of th... more Heavy ion collisions at intermediate energies offer the possibility to investigate the role of the isospin degree of freedom in determining the evolution of the reaction mechanism in an energy domain dominated by the competition between one body and two body nuclear dynamics. The REVERSE experiment has been carried on the period September 1999 - May 2000, at the Laboratory
De-excitation modes of compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40... more De-excitation modes of compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40 Ca and 86 Kr+ 48 Ca collisions at 10 A.MeV, are investigated. In particular, the competition between the various disintegration decay paths of medium mass compound nuclei, formed by fusion processes and the isospin (related to N/Z) of the entrance channel influence on the decay process, are studied. Data were taken at the INFN-Laboratori Nazionali del Sud (LNS) in ISODEC experiment, by using the CHIMERA array. The experiment complements and improves the previous experiment performed at GANIL where the same mechanisms were studied at lower excitation energies. The results show the presence of a relaxed component in the reaction mechanism, evident staggering effects in the Z distributions, as well as different isotopic composition and neutron enrichment for the reaction products in the two systems.
The skin nucleus 8 He is investigated by measuring the angular distribution of the elasticly scat... more The skin nucleus 8 He is investigated by measuring the angular distribution of the elasticly scattered 8 He and the 6,4 He fragments produced in the collision with a 208 Pb target at 22 MeV, just above the Coulomb barrier. The experiment was carried out at SPIRAL/GANIL in 2010. Here we present preliminary results for the elastic scattering.
Cross sections, kinetic energy and angular distributions of fragments with charge 6 ≤ Z ≤ 28 emit... more Cross sections, kinetic energy and angular distributions of fragments with charge 6 ≤ Z ≤ 28 emitted in 78,82 Kr +40 C at 5.5 MeV/A reactions were measured at the GANIL facility using the INDRA apparatus. This experiment aims to investigate the influence of the neutron enrichment on the decay mechanism of excited nuclei. Data are discussed in comparison with predictions of transition state and Hauser-Feshbach models.
For nuclear reactions in which super-heavy nuclei can be formed, the essential difference between... more For nuclear reactions in which super-heavy nuclei can be formed, the essential difference between the fusion process followed by fission and non-equilibrium processes leading to fissionlike fragments is the reaction time. Quite probable non-equilibrium processes, characterized by very short reaction times, are highlighted thanks to mass-angle correlations. However, long lifetime components associated with fission following fusion have been observed with two independent experimental techniques, providing evidence for the formation of compound nuclei with Z = 120 and 124, followed by mass asymmetric fission.
Physics of Unstable Nuclei - Proceedings of the International Symposium on the ISPUN07, 2008
By contrast to composite systems with Z = 120 and Z = 124, no evidence for long lifetime componen... more By contrast to composite systems with Z = 120 and Z = 124, no evidence for long lifetime components could be found for composite systems with Z = 114 formed in the reaction 208Pb + Ge at 6.16 MeV/u.
Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of ¹... more Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of ¹²Xe projectiles with ¹¹²Sn nuclei at E/A=50 MeV is examined. Charge correlations reveal that symmetric breakups occur with significant probability. By selecting on the parallel velocity of the heaviest fragment we minimize the entrance channel dynamics. Calculations with the statistical decay code GEMINI failed to reproduce the experimental
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