Saturation of the thermal energy deposited in Au and Th nuclei by Ar projectiles between 27 and 77 MeV/u

Jiang, D. X.; Doubre, H.; Galin, J.; Guerreau, D.; Piasecki, E.; Pouthas, J.; Sokolov, A.M.; Cramer, B.; Ingold, Gert‐Ludwig; Jahnke, U.; Schwinn, E.; Charvet, J. L.; Fréhaut, J.; Lott, B.; Magnago, C.; Morjean, M.; Patin, Y.; Pranal, Y.; Uzureau, J.; Gatty, B.; Jacquet, D.

doi:10.1016/0375-9474(89)90249-2

Cited by 63 publications

(15 citation statements)

References 26 publications

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“…A similar saturation has been observed in an earlier work by Jiang et al [48] using a completely different experimental method, based on the measurement of neutron multiplicities. The authors claimed the saturation of the thermal energy deposited in hot nuclei formed in collisions of Ar + Au and Ar + Th in the energy range 27-77 AMeV.…”

Section: Discussion Of Resultssupporting

confidence: 88%

“…In [48] the authors concluded that the observed saturation was due to the increasing inefficiency of the reac-tion mechanism to deposit thermal energy in to the hot nuclei it produced, rather than it being related to reaching the limits of excitation energy or temperature that a nucleus may support. In discussing the results of the present work we must ask ourselves the same question, but the situation is complicated by the fact that here we are dealing with several heated nuclei per event which may themselves result from the break-up of some other heavy, hot system.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

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Characteristics of the fragments produced in central collisions of129Xe+natSnfrom 32Ato 50AMeV

Hudan¹,

Chbihi²,

Frankland³

et al. 2003

Phys. Rev. C

106

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Characteristics of the primary fragments produced in central collisions of129 Xe + nat Sn from 32 to 50 AMeV have been obtained. By using the correlation technique for the relative velocity between light charged particles (LCP) and fragments, we were able to extract the multiplicities and average kinetic energy of secondary evaporated LCP. We then reconstructed the size and excitation energy of the primary fragments. For each bombarding energy a constant value of the excitation energy per nucleon over the whole range of fragment charge has been found. This value saturates at 3 AMeV for beam energies 39 AMeV and above. The corresponding secondary evaporated LCP represent less than 40% of all produced particles and decreases down to 23% for 50 AMeV. The experimental characteristics of the primary fragments are compared to the predictions of statistical multifragmentation model (SMM) calculations. Reasonable agreement between the data and the calculation has been found for any given incident energy. However SMM fails to reproduce the trend of the excitation function of the primary fragment excitation energy and the amount of secondary evaporated LCP's.

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Section: Discussion Of Resultssupporting

confidence: 88%

Section: Discussion Of Resultsmentioning

confidence: 99%

Characteristics of the fragments produced in central collisions of129Xe+natSnfrom 32Ato 50AMeV

Hudan¹,

Chbihi²,

Frankland³

et al. 2003

Phys. Rev. C

106

View full text Add to dashboard Cite

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“…By increasing the excitation energy from 150 to 1000 MeV for Au, the thus defined energy resolution decreases from 50% to 11% if deduced from M LCP , it increases from 12% to 23% for M n , and assumes a constant value of 7% for M LP . We conclude that M LP is indeed a reliable observation for E ‫ء‬ up to 1 GeV or more but that the observation of M n [13,15] and of M LCP [2] alone (which have been applied before for this purpose) is less sensitive to and the resolution depends strongly on the excitation energy. Since the next best choice are LCP's, at least for high excitation energies, we have also reconstructed the excitation energy distributions by using M LCP only.…”

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confidence: 91%

Heating of Nuclei with Energetic Antiprotons

Goldenbaum¹,

Bohne²,

Eades³

et al. 1996

Phys. Rev. Lett.

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The annihilation of energetic (1.2 GeV) antiprotons is exploited to deposit maximum thermal excitation (up to 1000 MeV) in massive nuclei (Cu, Ho, Au, and U) while minimizing the contribution from collective excitation such as rotation, shape distortion, and compression. Excitation energy distributions ds͞dE ‫ء‬ are deduced from eventwise observation of the whole nuclear evaporation chain with two 4p detectors for neutrons and charged particles. The nuclei produced in this way are found to decay predominantly statistically, i.e., by evaporation.[ S0031-9007(96) The study of such decay modes of very highly excited nuclei as fission, multifragmentation, cracking, and vaporization is presently a major objective in nuclear physics because of its bearing on the lesser-known bulk properties of hot nuclear matter, such as heat capacity, specific heat, viscosity, and phase transitions. Unfortunately, the decay pattern is also very sensitive to the dynamics of the excitation process, especially when collective degrees of freedom like rotation, shape distortion, and compression are strongly induced. These may have to be envisaged in the most often used [1-3] heavy-ion reactions. This ambiguity makes it difficult to correlate the observed decay pattern with either thermally or dynamically induced decay.In order to minimize the influence of the entrance channel on the decay modes, we have, for the first time, investigated the nuclear excitation following annihilation of energetic antiprotons. Antiprotons annihilate on a single nucleon at the surface of, or even inside the nucleus, thereby producing a pion cloud containing an average of about 5 particles. Because of the high centerof-mass velocity (b c.m.0.63) of this cloud, it is focused forward into the nucleus. Since the pion momenta are comparable to the Fermi momentum of the nucleons in the nucleus, the pions heat the nucleus in a soft radiationlike way [4], probably even softer and more efficient than can be expected in proton-or other lightion-induced spallation reactions, which have also been exploited recently for this purpose [5][6][7].Intranuclear cascade (INC) calculations have been found to provide a reasonable description of this mechanism. They predict that the spin remains low (below maximum 25h) and that shape distortion and density compression are negligible [8], in contrast to what is expected in heavy-ion reactions. The reaction time for achievement of equilibrium conditions is only about 30 fm͞c or 10 222 s [9], which is much shorter in general than the dynamical period in heavy-ion reactions [10]. This is all the more important at high temperature (T ഠ 6 MeV) when the characteristic evaporation time reduces to t , 10 222 s, implying little cooling of the compound nucleus during heating.In this Letter we concentrate on the use of a new method to determine the thermal excitation energy produced with energetic antiprotons. This method is based on the eventwise observation of the whole nuclear evaporation chain, including both neutrons and charged particles...

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“…The maximum amount of energy which can be stored in hot equilibrated nuclei has been studied both experimentally [1,2,3,4,5,6] and theoretically [7,8]. Such studies have mainly been motivated by the determination of a plateau in the so called caloric curve (the evolution of the temperature with the excitation energy) which could be a signature of a first order liquid-gas phase transition [9,10].…”

mentioning

confidence: 99%

Limitation of energy deposition in classicalNbody dynamics

Cussol

2003

Phys. Rev. C

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Energy transfers in collisions between classical clusters are studied with Classical N Body Dynamics calculations for different entrance channels. It is shown that the energy per particle transferred to thermalised classical clusters does not exceed the energy of the least bound particle in the cluster in its "ground state". This limitation is observed during the whole time of the collision, except for the heaviest system. PACS numbers: 24.10.Cn, 25.70.-z Keywords: Classical N-body dynamics, nucleus-nucleus collisions, energy depositionThe question of energy deposition in nuclei during nucleus-nucleus collisions is of great importance for nuclear matter studies. The maximum amount of energy which can be stored in hot equilibrated nuclei has been studied both experimentally [1,2,3,4,5,6] and theoretically [7,8]. Such studies have mainly been motivated by the determination of a plateau in the so called caloric curve (the evolution of the temperature with the excitation energy) which could be a signature of a first order liquid-gas phase transition [9,10].Experimentally, a lot of work has been done to determine the amount of thermal energy stored in nuclei. For central collisions, large energy deposits up to 22.5 A.MeV have been determined [9,11]. Other studies have shown that the excitation energy in primary products in multifragmenting systems is around 3-4 A.MeV [3,4,12,13], far below the total available energy in the center of mass frame. This energy does not seem to evolve strongly with the incident energy. These two measurements seem to be in contradiction. Possible limitations of energy deposition could result from prompt emission of energetic light charged particles at early times in the reaction [14,15,16].Theoretically, the maximum energy that a equilibrated nucleus can withstand corresponds to the energy (or temperature) at which the surface tension vanishes. This is often characterised by a critical temperature T c whose value is around 16 MeV [7,8]. This temperature is linked to the equation of state of nuclear matter. The main drawback of such studies is that they assume that the system is fully equilibrated and hence do not take into account possible limitations coming from the reaction mechanism.The aim of the present article is to study energy deposition during collisions between finite size systems in a well controlled framework. Results from the Classical N Body Dynamics code [17] will be shown and the mechanism of energy deposition in classical clusters will be studied. We will be interested in this paper by the energy transfered to thermally equilibrated clusters which corresponds to the energy that long-lived clusters can withstand. The paper is organised as follows. In a first section, the Classical N Body Dynamics will be briefly described. The excitation energy in clusters will be shown for various systems and incident energies in the second section. The third section will be devoted to the mechanism of energy deposition in clusters. Conclusions will be drawn in the last section I. DESCRIPT...

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Saturation of the thermal energy deposited in Au and Th nuclei by Ar projectiles between 27 and 77 MeV/u

Cited by 63 publications

References 26 publications

Characteristics of the fragments produced in central collisions of129Xe+natSnfrom 32Ato 50AMeV

Characteristics of the fragments produced in central collisions of129Xe+natSnfrom 32Ato 50AMeV

Heating of Nuclei with Energetic Antiprotons

Limitation of energy deposition in classicalNbody dynamics

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