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Graphical Environmental Tools for Application to Gamma-Ray Energy Tracking Arrays
In this CRADA, Oak Ridge National Laboratory (ORNL) assisted RIS Corporation of Knoxville, TN, in the development of graphical environment tools for the development and programming of high speed real-time algorithms to be implemented in a Field-Programmable Gate Array (FPGA). The primary application was intended to be digital signal processing for gamma-ray spectroscopy, in particular for Gamma-Ray Energy Tracking Arrays such as the GRETINA project. Key components of this work included assembling an evaluation platform to verify designs on actual hardware, and creating various types of Simulink functional blocks for peak-shaping and constant-fraction discrimination
K X-ray yields, M1 strength and the γ-ray quasicontinuum in 153Ho
The presence of highly converted transitions at high spin in the quasicontinuum spectrum of 153Ho was established from the measurement of K-shell ionization yields. The occurrence of these transitions and the onset of collectivity appear to be correlated. The quasicontinuum γ-ray spectrum was also measured. The X-ray yields cannot be explained solely by internal conversion of transitions with Eγ {slanted equal to or greater-than} 350 keV. Other sources are considered
Enhanced Fusion-Evaporation Cross Sections in Neutron-Rich Sn on Ni
Evaporation residue cross sections have been measured with neutron-rich
radioactive Sn beams on Ni in the vicinity of the Coulomb
barrier. The average beam intensity was particles per second
and the smallest cross section measured was less than 5 mb. Large subbarrier
fusion enhancement was observed. Coupled-channels calculations taking into
account inelastic excitation and neutron transfer underpredict the measured
cross sections below the barrier.Comment: 4 pages including 1 table and 3 figure
Anomalous Behavior of 2+ Excitations around 132Sn
In certain neutron-rich Te isotopes, a decrease in the energy of the first
excited 2+ state is accompanied by a decrease in the E2 strength to that state
from the ground state, contradicting simple systematics and general intuition
about quadrupole collectivity. We use a separable quadrupole-plus-pairing
Hamiltonian and the quasiparticle random phase approximation to calculate
energies, B(E2,0+ -> 2+) strengths, and g factors for the lowest 2+ states near
132Sn (Z >= 50). We trace the anomalous behavior in the Te isotopes to a
reduced neutron pairing above the N = 82 magic gap.Comment: 1 figure added. to be published in Phys. Rev.
Coexistence of 'alpha+ 208Pb' cluster structures and single-particle excitations in 212Po
Excited states in 212Po have been populated by alpha transfer using the
208Pb(18O,14C) reaction at 85MeV beam energy and studied with the EUROBALL IV
gamma multidetector array. The level scheme has been extended up to ~ 3.2 MeV
excitation energy from the triple gamma coincidence data. Spin and parity
values of most of the observed states have been assigned from the gamma angular
distributions and gamma -gamma angular correlations. Several gamma lines with
E(gamma) < 1 MeV have been found to be shifted by the Doppler effect, allowing
for the measurements of the associated lifetimes by the DSAM method. The
values, found in the range [0.1-0.6] ps, lead to very enhanced E1 transitions.
All the emitting states, which have non-natural parity values, are discussed in
terms of alpha-208Pb structure. They are in the same excitation-energy range as
the states issued from shell-model configurations.Comment: 21 pages, 19 figures, corrected typos, revised arguments in Sect.
III
Total -ray spectrum in Ho153: From the yrast line into the continuum
The radiation from Ho153 has been measured with Compton-suppressed Ge detectors. At least four components can be identified; the energy and spin removed by each of these have been measured, and their Doppler shifts analyzed. New fine structure is observed in the pre-yrast spectrum which arises from single-particle transitions forming the link between the yrast and continuum cascades. Near the yrast line the single-particle character of the states is preserved, but at higher energies collective modes begin to dominate
A one-dimensional lattice model for a quantum mechanical free particle
Two types of particles, A and B with their corresponding antiparticles, are
defined in a one dimensional cyclic lattice with an odd number of sites. In
each step of time evolution, each particle acts as a source for the
polarization field of the other type of particle with nonlocal action but with
an effect decreasing with the distance: A -->...\bar{B} B \bar{B} B \bar{B} ...
; B --> A \bar{A} A \bar{A} A ... . It is shown that the combined distribution
of these particles obeys the time evolution of a free particle as given by
quantum mechanics.Comment: 8 pages. Revte
Evaporation residue cross sections and average neutron multiplicities in the 64Ni+92Zr and 12C+144Sm reactions leading to 156Er
Evaporation residue cross sections and neutron multiplicity distributions have been measured for the 12C + 144Sm and 64Ni + 92Zr reactions leading to the same compound nucleous 156Er. Statistical model calculations can account for the data in the 12C-induced reaction. In contrast, the inhibition of neutron emission with respect to statistical model predictions seen in 64Ni + 92Zr cannot be explained even with the inclusion of the broad angular momentum distributions required to describe the fusion cross section data
Lifetime measurements in 184Pt and the shape coexistence picture
Lifetimes for levels in the yrast band of 184Pt have been measured up to spin 16+ using the recoil distance technique. The B(E2) values exhibit a marked increase in going from spin 2 to 10, consistent with a proposal that two bands of different deformations are mixing at low spin. This provides further support for shape coexistence occuring at low excitation energies in this region
Evolution of nuclear structure with increasing spin and internal excitation energy in 152Dy
The total γ ray spectrum emitted by 152Dy has been measured in two different reactions and decomposed into its constituent parts. From the measured decay times, multiplicities, multipolarities and spectral shapes, the average decay path has been reconstructed. The yrast single-particle structures have been shown to give way to highly collective bands at internal excitations energies > 1.5 MeV. A model, which takes into account the competition between statistical and collective decay at high spin and temperature, has been used to fit all features of the data, yielding Qt=7.0+2.5-1.5 e b for the collective bands
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