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Title: Disassembly of hot nuclear matter formed in Au-induced reactions near the Fermi energy

Abstract

Complex fragment emission has been studied in the 60 MeV/A 197Au + 12C, 27Al, 51V, natCu, and 197Au reactions. Velocity spectra, angular distributions and cross sections have been constructed for each target from the inclusive data. Coincidence data including 2-, 3-, 4-, and 5-fold events have also been examined. Furthermore neutron multiplicity distributions have been obtained for the above reactions by utilizing a novel neutron calorimetric approach.

Authors:
 [1]
  1. Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
10104778
Report Number(s):
LBL-34712
ON: DE94003260; TRN: 94:000223
DOE Contract Number:
AC03-76SF00098
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: TH: Thesis (Ph.D.); PBD: Sep 1993
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CARBON 12 TARGET; GOLD 197 REACTIONS; COPPER; VANADIUM 51 TARGET; GOLD 197 TARGET; ALUMINIUM 27 TARGET; NUCLEAR MATTER; PHASE TRANSFORMATIONS; NEUTRON DETECTORS; CALIBRATION; CROSS SECTIONS; 663450; 663520; 663530; 663540; 663550; 663580; HEAVY-ION-INDUCED REACTIONS AND SCATTERING; A = 6-19; A = 20-38; A = 39-58; A = 59-89; A = 190-219

Citation Formats

Delis, Dimitrios Nicholas. Disassembly of hot nuclear matter formed in Au-induced reactions near the Fermi energy. United States: N. p., 1993. Web. doi:10.2172/10104778.
Delis, Dimitrios Nicholas. Disassembly of hot nuclear matter formed in Au-induced reactions near the Fermi energy. United States. doi:10.2172/10104778.
Delis, Dimitrios Nicholas. Wed . "Disassembly of hot nuclear matter formed in Au-induced reactions near the Fermi energy". United States. doi:10.2172/10104778. https://www.osti.gov/servlets/purl/10104778.
@article{osti_10104778,
title = {Disassembly of hot nuclear matter formed in Au-induced reactions near the Fermi energy},
author = {Delis, Dimitrios Nicholas},
abstractNote = {Complex fragment emission has been studied in the 60 MeV/A 197Au + 12C, 27Al, 51V, natCu, and 197Au reactions. Velocity spectra, angular distributions and cross sections have been constructed for each target from the inclusive data. Coincidence data including 2-, 3-, 4-, and 5-fold events have also been examined. Furthermore neutron multiplicity distributions have been obtained for the above reactions by utilizing a novel neutron calorimetric approach.},
doi = {10.2172/10104778},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Sep 01 00:00:00 EDT 1993},
month = {Wed Sep 01 00:00:00 EDT 1993}
}

Thesis/Dissertation:
Other availability
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  • The decay of hot nuclei formed in the reactions 139La + 27Al, 51V, natCu, and 139La were studied by the coincident detection of up to four complex fragments (Z > 3) emitted in these reactions. Fragments were characterized as to their atomic number, energy and in- and out-of-plane angles. The probability of the decay by an event of a given complex fragment multiplicity as a function of excitation energy per nucleon of the source is nearly independent of the system studied. Additionally, there is no large increase in the proportion of multiple fragment events as the excitation energy of themore » source increases past 5 MeV/nucleon. This is at odds with many prompt multifragmentation models of nuclear decay. The reactions 139La + 27Al, 51V, natCu were also studied by combining a dynamical model calculation that simulates the early stages of nuclear reactions with a statistical model calculation for the latter stages of the reactions. For the reaction 139La + 27Al, these calculations reproduced many of the experimental features, but other features were not reproduced. For the reaction 139La + 51V, the calculation failed to reproduce somewhat more of the experimental features. The calculation failed to reproduce any of the experimental features of the reaction 139La + natCu, with the exception of the source velocity distributions.« less
  • This thesis contains the signficant results of an experiment designed to search for new nuclear states which might be produced in the interaction of nuclei with high energy protons. This experiment in which the nuclear fragment's charge, mass and kinetic energy were determined is described. Inclusive fragment isotopic yields and kinetic energy spectra are obtained through data analysis for fragment charge 3 less than or equal to Z/sub f/ less than or equal to 13 from Xenon and Krypton targets. The relative fragment mass yields are observed to follow a power law as a function of mass number with powermore » approx.2.65. The significance of this observation is explored through a study of phase transitions and critical phenomena. The fragmentation process is treated as condensation near the critical point. In analogy to a hot Van der Waals gas, fragmentation is envisaged as the formation of droplets of nucleons in an excited nuclear system near the critical point of nuclear matter. Fragments are interpreted as these droplets in a multibody nuclear disintegration. A critical temperature of 3.28 MeV is extracted. The fragment kinetic energy distributions are fit with a functional form which follows from the supposition that the fragments are formed inside an excited system. The characteristic 15 MeV slope of the K.E. spectra is interpreted as representative of the Fermi momentum. With the excitation temperature incorporated into the distribution the most probable Coulomb repulsion energies are obtained. Within a simple model these energies are translated into the most probable fragment locations inside the remnant which indicate that heavy fragments are formed predominantly near the remnant center.« less
  • The effect of free-particle collisions in simple ''knockout'' reactions of the form (a,aN) and in more complex nuclear reactions of the form (a,X) was investigated by using protons and pions. Cross sections for the 48Ti(p,2p) 47Sc and the 74Ge(p,2p) 73Ga reactions were measured from 0.3 to 4.6 GeV incident energy. The results indicate a rise in (p,2p) cross section for each reaction of about (25 ± 3) percent between the energies 0.3 and 1.0 GeV, and are correlated to a large increase in the total free-particle pp scattering cross sections over the same energy region. Results are compared to previousmore » (p,2p) excitation functions in the GeV energy region and to (p,2p) cross section calculations based on a Monte Carlo intranuclear cascade-evaporation model. Cross section measurements for (π ±, πN) and other more complex pion-induced spallation reactions were measured for the light target nuclei 14N, 16O, and 19F from 45 to 550 MeV incident pion energy. These measurements indicate a broad peak in the excitation functions for both (π,πN) and (π,X) reactions near 180 MeV incident energy. This corresponds to the large resonances observed in the free-particle π +p and π -p cross sections at the same energy. Striking differences in (π,πN) cross section magnitudes are observed among the light nuclei targets. The experimental cross section ratio sigma(π --n)/ sigma(π +,πN) at 180 MeV is 1.7 ± 0.2 for all three targets. The experimental results are compared to previous pion and analogous proton-induced reactions, to Monte Carlo intranuclear cascade-evaporation calculations, and to a semi-classical nucleon charge exchange model.« less
  • The ..delta..(1232) plays an important role in determining the properties of nuclear and neutron matter. The effects of the ..delta.. resonance are incorporated explicitly by using a coupled channel formalism. A method for constraining a lowest order variational calculation, appropriate when nucleon internal degrees of freedom are made explicity, is presented. Different N-N potentials were calculated and fit to phase shift data and deuteron properties. The potentials were constructed to test the relative importance of the ..delta.. resonance on nuclear properties. The symmetry energy and incompressibility of nuclear matter are generally reproduced by this calculation. Neutron matter results lead tomore » appealing neutron star models. Fermi liquid parameters for /sup 3/He are calculated with a model that includes both direct and induced terms. A convenient form of the direct interaction is obtained in terms of the parameters. The form of the direct interaction ensures that the forward scattering sum rule (Pauli principle) is obeyed. The parameters are adjusted to fit the experimentally determined F/sub 0//sup s/, F/sub 0//sup a/, and F/sub 1//sup s/ Landau parameters. Higher order Landau parameters are calculated by the self-consistent solution of the equations; comparison to experiment is good. The model also leads to a preferred value for the effective mass of /sup 3/He. Of the three parameters only one shows any dependence on pressure. An exact sum rule is derived relating this parameter to a specific summation of Landau parameters.« less