266 research outputs found
Cascade-Exciton Model Analysis of Nucleon-Induced Fission Cross Sections of Lead and Bismuth at Energies from 45 to 500 MeV
An extended version of the Cascade-Exciton Model (CEM) of nuclear reactions
is applied to analyze nucleon-induced fission cross sections for Bi-209 and
Pb-208 nuclei in the 45-500 MeV energy range. The available data on linear
momentum transfer are analyzed as well. The results are compared with
analytical approximations resulting from a comparative critical analysis of all
available experimental data. Systematic discrepancies between calculations and
experimental data are revealed. A modification of the CEM is proposed, which
significantly improves the model predictions for projectile energies above 100
MeV.Comment: 38 pages, 16 figures, 7 tables, LaTeX, submitted to Nucl. Sci. En
Superconducting Hilacs
We wish to report briefly on the progress of the Caltech study of the feasibility of building a superconducting hilac, and then to mention some points to stimulate further discussion
Fission-fragment mass distributions from strongly damped shape evolution
Random walks on five-dimensional potential-energy surfaces were recently
found to yield fission-fragment mass distributions that are in remarkable
agreement with experimental data. Within the framework of the Smoluchowski
equation of motion, which is appropriate for highly dissipative evolutions, we
discuss the physical justification for that treatment and investigate the
sensitivity of the resulting mass yields to a variety of model ingredients,
including in particular the dimensionality and discretization of the shape
space and the structure of the dissipation tensor. The mass yields are found to
be relatively robust, suggesting that the simple random walk presents a useful
calculational tool. Quantitatively refined results can be obtained by including
physically plausible forms of the dissipation, which amounts to simulating the
Brownian shape motion in an anisotropic medium.Comment: 14 pages, 11 ps figure
Current status of MCNP6 as a simulation tool useful for space and accelerator applications
For the past several years, a major effort has been undertaken at Los Alamos
National Laboratory (LANL) to develop the transport code MCNP6, the latest LANL
Monte-Carlo transport code representing a merger and improvement of MCNP5 and
MCNPX. We emphasize a description of the latest developments of MCNP6 at higher
energies to improve its reliability in calculating rare-isotope production,
high-energy cumulative particle production, and a gamut of reactions important
for space-radiation shielding, cosmic-ray propagation, and accelerator
applications. We present several examples of validation and verification of
MCNP6 compared to a wide variety of intermediate- and high-energy experimental
data on reactions induced by photons, mesons, nucleons, and nuclei at energies
from tens of MeV to about 1 TeV/nucleon, and compare to results from other
modern simulation tools.Comment: 4 pages, 3 figures, Proc. 11th Conference on the Intersections of
Particle and Nuclear Physics (CIPANP 2012), St. Petersburg, FL, May 28 - June
3, 201
Shape parametrization for liquid-drop studies
We present a new method for defining axially symmetric shapes which is particularly appropriate for describing elongated and multineck configurations. This shape parametrization is used to describe the static properties of incompressible, charged liquid drops. In particular, we calculate the properties of binary-fission saddle points and compare these with results using other methods. We also present the geometrical properties and normal mode analyses of the two-and three-necked saddle-point families
Pion-induced transport of π mesons in nuclei
A large body of data for pion-induced neutral pion continuum spectra spanning outgoing energies near 180 MeV shows no dip there that might be ascribed to internal strong absorption processes involving the formation of Δ’s. This is the same observation previously made for the charged pion continuum spectra. Calculations in an intranuclear cascade model or a cascade exciton model with free-space parameters predict such a dip for both neutral and charged pions. We explore several medium modifications to the interactions of pions with internal nucleons that are able to reproduce the data for nuclei from 7Li through Bi
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