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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

DPUNS--A Differential-Plunger For Lifetime Measurements Of Tagged Exotic/Unbound Nuclear States

This contribution focused on research to measure the lifetimes of unbound nuclear states using a differential-plunger technique combined with recoil-proton decay tagging. The results of the first lifetime measurements of unbound states in the spherical proton emitter, {sup 109}I, were discussed along with the limits to the technique. In order to proceed further, a new differential-plunger device, DPUNS, has been designed and is currently being built at the University of Manchester. DPUNS has been optimised to work with the GREAT/RITU/TDR setup at the University of Jyvaeskylae and the status of the new device is discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Experimental Studies Of An Exotic Decay Mode At The Proton Drip-Line: The Two-Proton Radioactivity

Two-proton radioactivity is an exotic decay mode for very proton-rich nuclei. It was observed experimentally for the first time in 2002 for the nucleus {sup 45}Fe but the two protons could not be directly detected. So a new detector has been developed, a Time Projection Chamber, to individually observe the two protons emitted. It was used successfully during two experiments for the study of {sup 45}Fe and {sup 54}Zn. Energy correlations have been studied and the relative angle between the two protons is calculated.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Direct Observation of Two Protons in the Decay of {sup 54}Zn

The two protons emitted in the decay of {sup 54}Zn have been individually observed for the first time in a time projection chamber. The total decay energy and the half-life measured in this work agree with the results obtained in a previous experiment. Angular and energy correlations between the two protons are determined and compared to theoretical distributions of a three-body model. Within the shell model framework, the relative decay probabilities show a strong contribution of the p{sup 2} configuration for the two-proton emission. After {sup 45}Fe, the present result on {sup 54}Zn constitutes only the second case of a direct observation of the ground state two-proton decay of a long-lived isotope.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Precision measurements of proton emission from the ground states of {sup 156}Ta and {sup 160}Re

The decays of the {pi}d{sub 3/2} ground states of {sup 156}Ta and {sup 160}Re have been studied in detail using the GREAT spectrometer. More than 7000 {sup 160}Re nuclei were produced in reactions of 290- and 300-MeV {sup 58}Ni ions with an isotopically enriched {sup 106}Cd target and separated in flight using the RITU separator. The proton and {alpha} decays of the {pi}d{sub 3/2} level were confirmed and the half-life and branching ratios of this state were determined with improved precision to be t{sub 1/2}=611{+-}7 {mu}s and b{sub p}=89{+-}1% and b{sub {alpha}=}11{+-}1%, respectively. The {alpha}-decay branch populated the ground state of {sup 156}Ta, allowing improved values for the proton-decay energy and half-life to be obtained (E{sub p}=1011{+-}5 keV; t{sub 1/2}=106{+-}4 ms). The {beta} decay of this level was identified for the first time and a branching ratio of b{sub {beta}=}29{+-}3% was deduced. The spectroscopic factors deduced from these measurements are compared with predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Assigning {gamma} deformation from fine structure in exotic nuclei

The nonadiabatic quasiparticle model for triaxial shapes is used to perform calculations for decay of {sup 141}Ho, the only known odd-Z even-N deformed nucleus for which fine structure in proton emission from both ground and isomeric states has been observed. All experimental data corresponding to this unique case namely, the rotational spectra of parent and daughter nuclei, decay widths and branching ratios for ground and isomeric states, could be well explained with a strong triaxial deformation {gamma}{approx}20. The recent experimental observation of fine structure decay from the isomeric state, can be explained only with an assignment of I{sup {pi}} = 3/2{sup +} as the decaying state, in contradiction with the previous assignment, of I{sup {pi}} 1/2{sup +}, based on adiabatic calculations. This study reveals that proton emission measurements could be a precise tool to probe triaxial deformations and other structural properties of exotic nuclei beyond the proton dripline.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Effects of isospin mixing in the A=32 quintet

For the A=32, T=2 quintet we provide a unified theoretical description for three related aspects of isospin mixing: the necessity of more than three terms in the isobaric mass multiplet equation, isospin-forbidden proton decay in {sup 32}Cl, and a correction to the allowed Fermi {beta}{sup +} decay of {sup 32}Ar. We demonstrate that all three effects observed in experiment can be traced to a common origin related to isospin mixing of the T=2 states with T=1 states.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Equilibrium and pre-equilibrium processes in the {sup 55}Mn({sup 6}Li,xp) and {sup 57}Fe({alpha},xp) reactions

Spectra of outgoing neutrons and protons from the {sup 6}Li + {sup 55}Mn reaction and protons from the {alpha} + {sup 57}Fe reaction have been measured with beams of 15-MeV {sup 6}Li ions and 30-MeV {alpha} particles. These reactions proceed through the same {sup 61}Ni nucleus at the same excitation energy, thus allowing the difference in reaction mechanisms to be studied. It is shown that spectra from the first reaction measured at backward angles are due to emission from a traditional compound nucleus reaction, in which the intermediate nucleus has reached statistical equilibrium; the spectra from the second reaction contain a significant fraction of pre-equilibrium emission at all angles. Level density parameters of the residual nucleus {sup 60}Co have been obtained from the first reaction. Both emission spectra and angular distributions have been measured for the second reaction. It was found that the pre-equilibrium component exhibits a forward-peaked angular distribution, as expected, but with a steeper slope than predicted and with an unusual slight rise at angles above 120 deg. The backward-angle rise is explained qualitatively by the dominance of the multistep compound mechanism at backward angles.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Nuclear Data Sheets for A = 56

The 1999 publication of Nuclear Data Sheets for A=56 (1999Hu04) has been updated using experimental nuclear structure data and decay data available before November 2009. The information for {sup 56}K, {sup 56}Ca, {sup 56}Sc, {sup 56}Ti, {sup 56}V, {sup 56}Cr, {sup 56}Mn, {sup 56}Fe, {sup 56}Co, {sup 56}Ni, {sup 56}Cu, and {sup 56}Zn from various reaction and decay experiments together with their adopted levels and {gamma} transition properties is summarized and presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Nuclear Data Sheets for A = 33

The experimental data are evaluated for known nuclides of mass number A=33 (Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K). Detailed evaluated level properties and related information are presented, including adopted values of level and {gamma}-ray energies, decay data (energies, intensities and placement of radiations), and other spectroscopic data. This work supersedes earlier full evaluations of A=33 published by 1990En08 (also 1998En04 update) and 1978En02. Experimental studies for the identification of the {sup 33}Ne and {sup 33}K nuclides have not met with success as yet. Values of S(n) and S(p) from systematics for {sup 33}Ne and {sup 33}K, respectively suggest that these nuclei are likely to be unstable to particle emission. The radioactive decay schemes of {sup 33}Na and {sup 33}Al seem incomplete in view of large Q values and known excitations much below than allowed by the Q values. The {sup 33}S and {sup 33}Cl nuclides remain as the most extensively studied from many different reactions and decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

The puzzle of {sup 32}Mg

An analysis of results of the {sup 30}Mg(t,p) {sup 32}Mg reaction demonstrates that the ground state is the normal state and the excited 0{sup +} state is the intruder, contrary to popular belief. Additional experiments are suggested.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Cu-67 Photonuclear Production

Cu-67 is considered as one of the most promising radioisotopes for cancer therapy with monoclonal antibodies. Current production schemes using high-flux reactors and cyclotrons do not meet potential market need. In this paper we discuss Cu-67 photonuclear production through the reaction Zn-68({gamma},p)Cu-67. Computer simulations were done together with experiments to study and optimize Cu-67 yield in natural Zn target. The data confirms that the photonuclear method has potential to produce large quantities of the isotope with sufficient purity to be used in medical field.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2019

Defining Processing Times for Accelerator Produced 225Ac and Other Isotopes from Proton Irradiated Thorium

During the purification of radioisotopes, decay periods or time dependent purification steps may be required to achieve a certain level of radiopurity in the final product. Actinum-225 (Ac-225), Silver-111 (Ag-111), Astatine-211 (At-211), Ruthenium-105 (Ru-105), and Rhodium-105 (Rh-105) are produced in a high energy proton irradiated thorium target. Experimentally measured cross sections, along with MCNP6-generated cross sections, were used to determine the quantities of Ac-225, Ag-111, At-211, Ru-105, Rh-105, and other co-produced radioactive impurities produced in a proton irradiated thorium target at Brookhaven Linac Isotope Producer (BLIP). Ac-225 and Ag-111 can be produced with high radiopurity by the proton irradiation of a thorium target at BLIP.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2011

Emergence of the N=16 shell gap in {sup 21}O

The spectroscopy of {sup 21}O has been investigated using a radioactive {sup 20}O beam and the (d,p) reaction in inverse kinematics. The ground and first excited states have been determined to be J{sup {pi}=}5/2{sup +} and 1/2{sup +}, respectively. Two neutron unbound states were observed at excitation energies of 4.77(10) and 6.17(11) MeV. The spectroscopic factor deduced for the lower of these, interpreted as a 3/2{sup +} level, reveals a relatively pure (60%) 0d{sub 3/2} single-particle configuration, in good agreement with shell-model calculations that predict {sup 26}O to be unbound. The large energy difference between the 3/2{sup +} and 1/2{sup +} states is indicative of the emergence of the N=16 shell gap, which is estimated to be 5.1(11) MeV. For the higher-lying resonance, which has a character consistent with a spin-parity assignment of 3/2{sup +} or 7/2{sup -}, a 0.71(22) branching ratio to the first 2{sup +} state in {sup 20}O has been observed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗