Hot nuclei as viewed through 4 pi neutron multiplicity filters

Galin, J.; Jahnke, U.

doi:10.1088/0954-3899/20/8/005

Cited by 43 publications

(27 citation statements)

References 107 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The BNB [11] is a spherical tank with an outer diameter of 140 cm and a scintillator volume of 1500 l, housing a reaction chamber of 40 cm diameter at the center of which the targets were located. This detector was mainly used for counting evaporationlike neutrons in each reaction.…”

mentioning

confidence: 99%

“…For these low-energy neutrons, its efficiency was typically e ϳ ͑83285͒%. For cascade neutrons of higher energy (30-50 MeV), the efficiency decreases to the (40-25)% level [11], which means that the detector is rather transparent to neutrons from pre-equilibrium processes. The master trigger for the acquisition system was a coincidence of S1^S0 and the prompt light signal of the BNB, with the threshold set to ഠ10 MeV.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Heating of Nuclei with Energetic Antiprotons

Goldenbaum¹,

Bohne²,

Eades³

et al. 1996

Phys. Rev. Lett.

View full text Add to dashboard Cite

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...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Heating of Nuclei with Energetic Antiprotons

Goldenbaum¹,

Bohne²,

Eades³

et al. 1996

Phys. Rev. Lett.

View full text Add to dashboard Cite

show abstract

“…Such a limitation has been observed in the fragmentation of Uranium projectiles at relativistic energies [4]. This limitation was also suggested by the observation of the saturation of the evaporated neutron multiplicity when the incident energy increases [5].…”

Section: Discussionmentioning

confidence: 69%

“…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

View full text Add to dashboard Cite

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...

show abstract

“…Calculation of neutron production and neutron multiplicity distributions have been performed for proton, pion (π + , π − ), antiproton (p − ), H 2 , He 3 -induced spallation/fission reaction in the energy range from ∼0.5 GeV up to 5.0 GeV on Ag, Au, Ta, Pb, Bi, U targets of various geometries. The most detailed measurements of neutron multiplicity distributions were carried out in [11][12][13] with a 4π neutron detector with the mean efficiency ϵ about 70-80% [13]. Figures 3 and 4 show the results of simulations for neutron multiplicity distributions performed with from 2.0 GeV proton-and 2.0 GeV He 3 -induced reactions on Ag, Au, Bi, U thin targets.…”

Section: Nuclear Reactions On Thin and Thick Targetsmentioning

confidence: 99%

QGSM development for spallation reactions modeling

Baznat

Chigrinov

Gudima

2012

EPJ Web of Conferences

View full text Add to dashboard Cite

Abstract. The growing interest in spallation neutron sources, accelerator-driven systems, R&D of rare isotope beams, and development of external beam radiation therapy necessitated the improvement of nuclear reaction models for both stand-alone codes for the analysis of nuclear reactions and event generators within the Monte Carlo transport systems for calculations of interactions of high-energy particles with matter in a wide range of energy and in arbitrary 3D geometry of multicomponent targets. The exclusive approach to the description of nuclear reactions is the most effective for detailed calculation of inelastic interactions with atomic nuclei. It provides the correct description of particle production, single-and double-differential spectra, recoil, and fission product yields. This approach has been realized in the Quark Gluon String Model (QGSM) for nuclear reactions induced by photons, hadrons, and high energy heavy ions. In this article, improved versions of the QGSM model and a corresponding code have been developed tested and bench marked against experimental data for neutron production in spallation reactions on thin and thick targets in the energy range from a few MeV to several GeV/nucleon.

show abstract

Hot nuclei as viewed through 4 pi neutron multiplicity filters

Cited by 43 publications

References 107 publications

Heating of Nuclei with Energetic Antiprotons

Heating of Nuclei with Energetic Antiprotons

Limitation of energy deposition in classicalNbody dynamics

QGSM development for spallation reactions modeling

Contact Info

Product

Resources

About