10,854 research outputs found
Incorporating Radial Flow in the Lattice Gas Model for Nuclear Disassembly
We consider extensions of the lattice gas model to incorporate radial flow.
Experimental data are used to set the magnitude of radial flow. This flow is
then included in the Lattice Gas Model in a microcanonical formalism. For
magnitudes of flow seen in experiments, the main effect of the flow on
observables is a shift along the axis.Comment: Version accepted for publication in Phys. Rev. C, Rapid Communicatio
Temperature determination from the lattice gas model
Determination of temperature from experimental data has become important in
searches for critical phenomena in heavy ion collisions. Widely used methods
are ratios of isotopes (which rely on chemical and thermal equilibrium),
population ratios of excited states etc. Using the lattice gas model we propose
a new observable: where is the charge multiplicity and
is the charge of the fragmenting system. We show that the reduced multiplicity
is a good measure of the average temperature of the fragmenting system.Comment: 11 pages, 2 ps file
Tracking the phase-transition energy in disassembly of hot nuclei
In efforts to determine phase transitions in the disintegration of highly
excited heavy nuclei, a popular practice is to parametrise the yields of
isotopes as a function of temperature in the form
, where 's are the measured yields
and and are fitted to the yields. Here would be
interpreted as the phase transition temperature. For finite systems such as
those obtained in nuclear collisions, this parametrisation is only approximate
and hence allows for extraction of in more than one way. In this work we
look in detail at how values of differ, depending on methods of
extraction. It should be mentioned that for finite systems, this approximate
parametrisation works not only at the critical point, but also for first order
phase transitions (at least in some models). Thus the approximate fit is no
guarantee that one is seeing a critical phenomenon. A different but more
conventional search for the nuclear phase transition would look for a maximum
in the specific heat as a function of temperature . In this case is
interpreted as the phase transition temperature. Ideally and would
coincide. We invesigate this possibility, both in theory and from the ISiS
data, performing both canonical () and microcanonical ()
calculations. Although more than one value of can be extracted from the
approximate parmetrisation, the work here points to the best value from among
the choices. Several interesting results, seen in theoretical calculations, are
borne out in experiment.Comment: Revtex, 10 pages including 8 figures and 2 table
Model of multifragmentation, Equation of State and phase transition
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. We draw a p-V diagram for the model and compare with a p-V
diagram obtained from a mean-field theory. We investigate the question of
chemical instability in the multifragmentation model. Phase transitions in the
model are discussed.Comment: Revtex, 9 pages including 6 figures: some change in the text and Fig.
Caloric Curves for small systems in the Nuclear Lattice Gas Model
For pedagogical reasons we compute the caloric curve for 11 particles in a
lattice. Monte-Carlo simulation can be avoided and exact results are
obtained. There is no back-bending in the caloric curve and negative specific
heat does not appear. We point out that the introduction of kinetic energy in
the nuclear Lattice Gas Model modifies the results of the standard Lattice Gas
Model in a profound way.Comment: 12 pages, Revtex, including 4 postscript figure
Application of Solid Reductant Processes for Direct Reduction in India
Efforts to develop commercially acceptable direct redu-ction processes during the last two decades are possibly
a revival of efforts made in this direction some two cent-uries ago. In 1792, Samuel Lucas obtained a patent for converting iron ore to metal using charcoal as reductant. (1) Adrien Chenot also took a patent some time in the middle of the last century to produce sponge iron util-ising iron ore concentrates and charcoal in a retort. (2) There are many other names and attempts associated with the early development of direct reduction which are only of historic interest today
Isospin fluctuations in spinodal decomposition
We study the isospin dynamics in fragment formation within the framework of
an analytical model based on the spinodal decomposition scenario. We calculate
the probability to obtain fragments with given charge and neutron number,
focussing on the derivation of the width of the isotopic distributions. Within
our approach this is determined by the dispersion of N/Z among the leading
unstable modes, due to the competition between Coulomb and symmetry energy
effects, and by isovector-like fluctuations present in the matter that
undergoes the spinodal decomposition. Hence the widths exhibit a clear
dependence on the properties of the Equation of State. By comparing two systems
with different values of the charge asymmetry we find that the isotopic
distributions reproduce an isoscaling relationship.Comment: 18 RevTex4 pages, 6 eps figure
Microcanonical Lattice Gas Model for Nuclear Disassembly
Microcanonical calculations are no more difficult to implement than canonical
calculations in the Lattice Gas Model. We report calculations for a few
observables where we compare microcanonical model results with canonical model
results.Comment: 7 pages, Revtex, 3 postscript figure
The Liquid-Gas Phase Transitions in a Multicomponent Nuclear System with Coulomb and Surface Effects
The liquid-gas phase transition is studied in a multi-component nuclear
system using a local Skyrme interaction with Coulomb and surface effects. Some
features are qualitatively the same as the results of Muller and Serot which
uses relativistic mean field without Coulomb and surface effects. Surface
tension brings the coexistance binodal surface to lower pressure. The Coulomb
interaction makes the binodal surface smaller and cause another pair of binodal
points at low pressure and large proton fraction with less protons in liquid
phase and more protons in gas phase.Comment: 20 pages including 7 postscript figure
First Order Phase Transition in Intermediate Energy Heavy Ion Collisions
We model the disassembly of an excited nuclear system formed as a result of a
heavy ion collision. We find that, as the beam energy in central collisions in
varied, the dissociating system crosses a liquid-gas coexistence curve,
resulting in a first-order phase transition. Accessible experimental signatures
are identified: a peak in specific heat, a power-law yield for composites, and
a maximum in the second moment of the yield distribution
- âŠ