43 research outputs found
CEM2k and LAQGSM as Event Generators for Space-Radiation-Shielding and Cosmic-Ray-Propagation Applications
The CEM2k and LAQGSM codes have been recently developed at Los Alamos
National Laboratory to simulate nuclear reactions for a number of applications.
We have benchmarked our codes against most available measured data at incident
particle energies from 10 MeV to 800 GeV and have compared our results with
predictions of other current models used by the nuclear community. Here, we
present a brief description of our codes and show illustrative results to show
that CEM2k and LAQGSM can be used as reliable event generators for
space-radiation-shielding, cosmic-ray-propagation, and other astrophysical
applications. Finally, we show the use of our calculated cross sections
together with experimental data from our LANL T-16 compilation to produce
evaluated files which we use in the GALPROP model of galactic particle
propagation to better constrain the size of the CR halo.Comment: 10 pages, 9 figures, LaTeX, talk given at the World Space Congress
2002, 34th COSPAR Scientific Assembly, Houston, Texas, USA, 10-19 October
2002, to appear in Advances in Space Researc
CEM03.03 and LAQGSM03.03 Event Generators for the MCNP6, MCNPX, and MARS15 Transport Codes
A description of the IntraNuclear Cascade (INC), preequilibrium, evaporation,
fission, coalescence, and Fermi breakup models used by the latest versions of
our CEM03.03 and LAQGSM03.03 event generators is presented, with a focus on our
most recent developments of these models. The recently developed "S" and "G"
versions of our codes, that consider multifragmentation of nuclei formed after
the preequilibrium stage of reactions when their excitation energy is above 2A
MeV using the Statistical Multifragmentation Model (SMM) code by Botvina et al.
("S" stands for SMM) and the fission-like binary-decay model GEMINI by Charity
("G" stands for GEMINI), respectively, are briefly described as well. Examples
of benchmarking our models against a large variety of experimental data on
particle-particle, particle-nucleus, and nucleus-nucleus reactions are
presented. Open questions on reaction mechanisms and future necessary work are
outlined.Comment: 94 pages, 51 figures, 5 tables, invited lectures presented at the
Joint ICTP-IAEA Advanced Workshop on Model Codes for Spallation Reactions,
February 4-8, 2008, ICTP, Trieste, Italy; corrected typos and reference
Propagation of secondary antiprotons and cosmic rays in the Galaxy
Recent measurements of the cosmic ray (CR) antiproton flux have been shown to
challenge existing CR propagation models. It was shown that the reacceleration
models designed to match secondary to primary nuclei ratios (e.g., B/C) produce
too few antiprotons. In the present paper we discuss one possibility to
overcome these difficulties. Using the measured antiproton flux AND B/C ratio
to fix the diffusion coefficient, we show that the spectra of primary nuclei as
measured in the heliosphere may contain a fresh local "unprocessed" component
at low energies perhaps associated with the Local Bubble, thus decreasing the
measured secondary to primary nuclei ratio. The independent evidence for SN
activity in the solar vicinity in the last few Myr supports this idea. The
model reproduces antiprotons, B/C ratio, and elemental abundances up to Ni
(Z<=28). Calculated isotopic distributions of Be and B are in perfect agreement
with CR data. The abundances of three "radioactive clock" isotopes in CR, 10Be,
26Al, 36Cl, are all consistent and indicate a halo size z_h~4 kpc based on the
most accurate data taken by the ACE spacecraft.Comment: 6 pages, 5 ps-figures, cospar.sty; Proc. of 34th COSPAR Scientific
Assembly (Houston, 10-19 October 2002). Submitted to Advances in Space
Research. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
High Energy Activation Data Library (HEAD-2009)
A proton activation data library for 682 nuclides from 1-H to 210-Po in the
energy range from 150 MeV up to 1 GeV was developed. To calculate proton
activation data, the MCNPX 2.6.0 and CASCADE/INPE codes were chosen. Different
intranuclear cascade, preequilibrium, and equilibrium nuclear reaction models
and their combinations were used. The optimum calculation models have been
chosen on the basis of statistical correlations for calculated and experimental
proton data taken from the EXFOR library of experimental nuclear data. All the
data are written in ENDF-6 format. The library is called HEPAD-2008
(High-Energy Proton Activation Data). A revision of IEAF-2005 neutron
activation data library has been performed: A set of nuclides for which the
cross-section data can be (and were) updated using more modern and improved
models is specified, and the corresponding calculations have been made in the
present work. The new version of the library is called IEAF-2009. The
HEPAD-2008 and IEAF-2009 are merged to the final HEAD-2009 library.Comment: 21 pages, 10 tables, 3 figures, only pdf, submitted to Nucl. Instrum.
Meth.
Small-angle fragmentation of carbon ions at 0.6 GeV/n: a comparison with models of ion-ion interactions
Momentum distributions of hydrogen and helium isotopes from 12C fragmentation at 3.5° were measured at 0.6 GeV/nucleon in the FRAGM experiment at ITEP TWA heavy ion accelerator. The fragments were selected by correlated time of flight and dE/dx measurements with a magnetic spectrometer with scintillation counters. The main attention was drawn to the high momentum region where the fragment velocity exceeds the velocity of the projectile nucleus. The momentum spectra of fragments span the region of the fragmentation peak as well as the cumulative region. The differential cross sections cover six orders of magnitude. The distributions measured are compared to the predictions of three ion-ion interaction models: BC, QMD and LAQGSM03.03. The kinetic energy spectra of fragments in the projectile rest frame have an exponential shape with two temperatures, being defined by their slope parameters
Spallation reactions. A successful interplay between modeling and applications
The spallation reactions are a type of nuclear reaction which occur in space
by interaction of the cosmic rays with interstellar bodies. The first
spallation reactions induced with an accelerator took place in 1947 at the
Berkeley cyclotron (University of California) with 200 MeV deuterons and 400
MeV alpha beams. They highlighted the multiple emission of neutrons and charged
particles and the production of a large number of residual nuclei far different
from the target nuclei. The same year R. Serber describes the reaction in two
steps: a first and fast one with high-energy particle emission leading to an
excited remnant nucleus, and a second one, much slower, the de-excitation of
the remnant. In 2010 IAEA organized a worskhop to present the results of the
most widely used spallation codes within a benchmark of spallation models. If
one of the goals was to understand the deficiencies, if any, in each code, one
remarkable outcome points out the overall high-quality level of some models and
so the great improvements achieved since Serber. Particle transport codes can
then rely on such spallation models to treat the reactions between a light
particle and an atomic nucleus with energies spanning from few tens of MeV up
to some GeV. An overview of the spallation reactions modeling is presented in
order to point out the incomparable contribution of models based on basic
physics to numerous applications where such reactions occur. Validations or
benchmarks, which are necessary steps in the improvement process, are also
addressed, as well as the potential future domains of development. Spallation
reactions modeling is a representative case of continuous studies aiming at
understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie