629 research outputs found
Vibration measurement by pulse differential holographic interferometry
Technique measures structural deformation of materials subjected to wide range of temperatures and other environmental conditions. Effects of convection currents are eliminated by operating a pulsed laser in double pulse mode that exposes hologram twice in quick succession
The impact of global nuclear mass model uncertainties on -process abundance predictions
Rapid neutron capture or `-process' nucleosynthesis may be responsible for
half the production of heavy elements above iron on the periodic table. Masses
are one of the most important nuclear physics ingredients that go into
calculations of -process nucleosynthesis as they enter into the calculations
of reaction rates, decay rates, branching ratios and Q-values. We explore the
impact of uncertainties in three nuclear mass models on -process abundances
by performing global monte carlo simulations. We show that root-mean-square
(rms) errors of current mass models are large so that current -process
predictions are insufficient in predicting features found in solar residuals
and in -process enhanced metal poor stars. We conclude that the reduction of
global rms errors below keV will allow for more robust -process
predictions.Comment: 5 pages, 3 figures, invited talk at the 15th International Symposium
on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15), to appear in
EPJ Web of Conference
Applications of holography to vibrations, transient response, and wave propagation
Applications of holography to vibrations, transient response, and wave propagatio
The sensitivity of r-process nucleosynthesis to the properties of neutron-rich nuclei
About half of the heavy elements in the Solar System were created by rapid
neutron capture, or r-process, nucleosynthesis. In the r-process, heavy
elements are built up via a sequence of neutron captures and beta decays in
which an intense neutron flux pushes material out towards the neutron drip
line. The nuclear network simulations used to test potential astrophysical
scenarios for the r-process therefore require nuclear physics data (masses,
beta decay lifetimes, neutron capture rates, fission probabilities) for
thousands of nuclei far from stability. Only a small fraction of this data has
been experimentally measured. Here we discuss recent sensitivity studies that
aim to determine the nuclei whose properties are most crucial for r-process
calculations.Comment: 8 pages, 4 figures, submitted to the Proceedings of the Fifth
International Conference on Fission and Properties of Neutron-Rich Nuclei
(ICFN5
Sensitivity of the r-process to nuclear masses
The rapid neutron capture process (r-process) is thought to be responsible
for the creation of more than half of all elements beyond iron. The scientific
challenges to understanding the origin of the heavy elements beyond iron lie in
both the uncertainties associated with astrophysical conditions that are needed
to allow an r-process to occur and a vast lack of knowledge about the
properties of nuclei far from stability. There is great global competition to
access and measure the most exotic nuclei that existing facilities can reach,
while simultaneously building new, more powerful accelerators to make even more
exotic nuclei. This work is an attempt to determine the most crucial nuclear
masses to measure using an r-process simulation code and several mass models
(FRDM, Duflo-Zuker, and HFB-21). The most important nuclear masses to measure
are determined by the changes in the resulting r-process abundances. Nuclei
around the closed shells near N=50, 82, and 126 have the largest impact on
r-process abundances irrespective of the mass models used.Comment: 5 pages, 4 figures, accepted in European Physical Journal
Sensitivity studies for r-process nucleosynthesis in three astrophysical scenarios
In rapid neutron capture, or r-process, nucleosynthesis, heavy elements are
built up via a sequence of neutron captures and beta decays that involves
thousands of nuclei far from stability. Though we understand the basics of how
the r-process proceeds, its astrophysical site is still not conclusively known.
The nuclear network simulations we use to test potential astrophysical
scenarios require nuclear physics data (masses, beta decay lifetimes, neutron
capture rates, fission probabilities) for all of the nuclei on the neutron-rich
side of the nuclear chart, from the valley of stability to the neutron drip
line. Here we discuss recent sensitivity studies that aim to determine which
individual pieces of nuclear data are the most crucial for r-process
calculations. We consider three types of astrophysical scenarios: a traditional
hot r-process, a cold r-process in which the temperature and density drop
rapidly, and a neutron star merger trajectory.Comment: 8 pages, 4 figures, submitted to the Proceedings of the International
Nuclear Physics Conference (INPC) 201
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Predictions for nuclear properties along the r-process path
The uniformity of different nuclear regions as a function of the number of valence protons and neutrons (counted from the nearest closed shell) has been exploited for the parameterization of calculations for nuclei far from stability within the IBA model. Predictions are given for low lying levels, E2 transition rates, and binding energies for nuclei in the r-process path in the A = 150 and A = 190 mass regions. 6 refs., 6 figs
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