314 research outputs found
Universality of the p process
The solar abundances provide a concept of universality that the abundance ratios of the p-nucleus to the s-nucleus with the same atomic number are almost constant with the wide region for materials produced by individual stellar nucleosynthesis episode. We study this universality using g -process calculations with core-collapse supernova explosions under various conditions. The calculated results show that the g -process under the various conditions can occur but the ratios are almost constant with the wide region independent of the conditions. The shift of g -process layers, weak s-process and the b -decay after the g -process contribute to the manifestation of the universality
STUDY ON EMITTANCE DILUTION IN THE JAERI-FEL ENERGY-RECOVERY TRANSPORT
Abstract An isochronous recirculating beam transport is under construction at the JAERI-FEL facility for energy-recovery experiments, where FEL output power over 2kW will be available. Since the FEL performance depends largely on the beam emittance, it is important to estimate emittance dilution along the recirculation. In the present paper, we study the emittance dilution in our recirculating transport, which is caused by higher-order aberrations, space charge force and coherent synchrotron radiation force
Second Backbend in the Mass A ~ 180 Region
Within the framework of selfconsistent cranked Hartree-Fock- Bogoliubov
theory(one-dimensional) we predict second backbend in the yrast line of Os-182
at , which is even sharper than the first one observed
experimentally at .
Around such a high spin the structure becomes multi-quasiparticle type, but
the main source of this strong discontinuity is a sudden large alignment of
i_13/2 proton orbitals along the rotation axis followed soon by the alignment
of j_15/2 neutron orbitals. This leads to drastic structural changes at such
high spins. When experimentally confirmed, this will be observed for the first
time in this mass region, and will be at the highest spin so far.Comment: 13 pages, 4 ps figure
Nuclear structure of 30S and its implications for nucleosynthesis in classical novae
The uncertainty in the 29P(p,gamma)30S reaction rate over the temperature
range of 0.1 - 1.3 GK was previously determined to span ~4 orders of magnitude
due to the uncertain location of two previously unobserved 3+ and 2+ resonances
in the 4.7 - 4.8 MeV excitation region in 30S. Therefore, the abundances of
silicon isotopes synthesized in novae, which are relevant for the
identification of presolar grains of putative nova origin, were uncertain by a
factor of 3. To investigate the level structure of 30S above the proton
threshold (4394.9(7) keV), a charged-particle spectroscopy and an in-beam
gamma-ray spectroscopy experiments were performed. Differential cross sections
of the 32S(p,t)30S reaction were measured at 34.5 MeV. Distorted wave Born
approximation calculations were performed to constrain the spin-parity
assignments of the observed levels. An energy level scheme was deduced from
gamma-gamma coincidence measurements using the 28Si(3He,n-gamma)30S reaction.
Spin-parity assignments based on measurements of gamma-ray angular
distributions and gamma-gamma directional correlation from oriented nuclei were
made for most of the observed levels of 30S. As a result, the resonance
energies corresponding to the excited states in 4.5 MeV - 6 MeV region,
including the two astrophysically important states predicted previously, are
measured with significantly better precision than before. The uncertainty in
the rate of the 29P(p,gamma)30S reaction is substantially reduced over the
temperature range of interest. Finally, the influence of this rate on the
abundance ratios of silicon isotopes synthesized in novae are obtained via 1D
hydrodynamic nova simulations.Comment: 22 pages, 12 figure
Photo-disintegration cross section measurements on W, Re and Os: Implications for the Re-Os cosmochronology
Cross sections of the W, Re, Os() reactions
were measured using quasi-monochromatic photon beams from laser Compton
scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are
compared with the predictions of Hauser-Feshbach statistical calculations using
four different sets of input parameters. In addition, the inverse neutron
capture cross sections were evaluated by constraining the model parameters,
especially the strength function, on the basis of the experimental data.
The present experiment helps to further constrain the correction factor
for the neutron capture on the 9.75 keV state in Os.
Implications of to the Re-Os cosmochronology are discussed with a
focus on the uncertainty in the estimate of the age of the Galaxy.Comment: 11 page
Superdeformation in Asymmetric NZ Nucleus Ar
A rotational band with five -ray transitions ranging from 2 to
12 states was identified in Ar. This band is linked through
transitions from the excited 2, 4 and 6 levels to
the low-lying states; this determines the excitation energy and the spin-parity
of the band. The deduced transition quadrupole moment of 1.45 indicates that the band has a superdeformed shape. The nature of the band
is revealed by cranked Hartree--Fock--Bogoliubov calculations and a
multiparticle--multihole configuration is assigned to the band
s -process branching at W 185 revised
The neutron capture cross section of the unstable s-process branching nucleus
185W has been derived from experimental data of the inverse 186W(g,n)185W
photodisintegration taken with monochromatic photon beams from laser Compton
scattering. The result of sigma = 553 +- 60 mb at kT = 30 keV leads to a
relatively high effective neutron density in the classical s-process of N_n =
4.7 \times 10^8 cm^-3. A realistic model for the s-process in thermally pulsing
AGB stars overestimates the abundance of 186Os significantly because of the
relatively small neutron capture cross section of 185W.Comment: 10 pages, 3 figure
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