Engineering topics

Greene, J. P.

Publications and source records attributed to Greene, J. P..

23 records · Page 2

DOE OSTI2020

Study of the ${{^{25}}}$Mg(d,p)${{^{26}}}$Mg reaction to constrain the ${{^{25}}}$Al(p,${\gamma }$)${{^{26}}}$Si resonant reaction rates in nova burning conditions

The rate of the 25 Al( p,γ) 26 Si reaction is one of the few key remaining nuclear uncertainties required for predicting the production of the cosmic γ-ray emitter 26 Al in explosive burning in novae. This reaction rate is dominated by three key resonances (J π = 0 + , 1 + and 3 + ) in 26 Si. Only the 3 + resonance strength has been directly constrained by experiment. A high resolution measurement of the 25 Mg(d, p) reaction was used to determine spectroscopic factors for analog states in the mirror nucleus, 26 Mg. A first spectroscopic factor value is reported for the 0 + state at 6.256 MeV, and a strict upper limit is set on the value for the 1 + state at 5.691 MeV, that is incompatible with an earlier ( 4 He, 3 He) study. These results are used to estimate proton partial widths, and resonance strengths of analog states in 26 Si contributing to the 25 Al( p,γ) 26 Si reaction rate in nova burning conditions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2019

Fast-timing measurements in the ground-state band of Pd 114

Using a hybrid Gammasphere array coupled to 25 LaBr 3 ( Ce ) detectors, the lifetimes of the first three levels of the yrast band in Pd 114 , populated via Cf 252 decay, have been measured. The measured lifetimes are τ 2 + = 103 ( 10 ) ps , τ 4 + = 22 ( 13 ) ps , and τ 6 + ≤ 10 ps for the 2 1 + , 4 1 + , and 6 1 + levels, respectively. Palladium-114 was previously predicted to be the most deformed isotope of its isotopic chain, and spectroscopic studies have suggested it might also be a candidate nucleus for low-spin stable triaxiality. From the lifetimes measured here, reduced transition probabilities B ( E 2 ; J → J - 2 ) are calculated and compared with interacting boson model, projected shell model, and collective model calculations from the literature. The experimental ratio R B ( E 2 ) = B ( E 2 ; 4 1 + → 2 1 + ) / B ( E 2 ; 2 1 + → 0 1 + ) = 0.80 ( 42 ) is measured for the first time in Pd 114 and compared with the known values R B ( E 2 ) in the palladium isotopic chain: the systematics suggest that, for N = 68 , a transition from γ -unstable to a more rigid γ -deformed nuclear shape occurs.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2019

Isotopic carbon targets

Neutron-rich isotopic 14 C targets are of interest to the nuclear physics community and would be in high demand at any thickness. Applied Nanotech, Inc. (ANI) has developed freestanding nat C and 13 C carbon foils fabricated using a drawdown printing technique. Isotopic enriched 13 C targets are produced at ANI, with the 14 C targets to be fabricated at Argonne National Laboratory (ANL) using stock material available at Argonne. The 14 C target material is nominally enriched to ~73% 14 C and will contain 2.2% organic binder. The fabrication process is highly material-efficient and can be used to produce targets that are difficult to fabricate by other methods. Finally, to be developed, 12 C ( 13 C-depleted natural carbon) which could also be used in accelerators for target applications.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2019

Isotopic targets with graphene backing

Many of the isotopes cannot be made as free-standing targets and require thin film backing. Low-Z backing materials, such as amorphous carbon and thin polymer films are materials of choice for some experiments. However, the limitations of these backing materials are poor thermal and mechanical stability. All-carbon graphene films would be an excellent choice as a backing material due to their high thermal conductivity, high temperature tolerance (3550ºC melting point), low outgassing, mechanical integrity, and ease of handling. We fabricated a variety of targets using graphene material as a backing or a host matrix. Using PVD sputtering deposition of boron-11 carbide, we fabricated 11 B target with a 0.5 mg/cm 2 on graphene film. The 11 B isotope is of interest due to aneutronic proton–boron fusion reaction 1 p + 11 B → 3 4 He + 8.7 MeV suitable for clean energy production1. We also prepared a neutron rich natCr target on graphene backing by electroplating Cr in an aqueous chromium (III) oxide bath. The chromium target can be used for production of positron emitting Mn radioisotope2 in the reaction 52 Cr (p,n) 52 Mn. One of the unique advantages of the graphene film fabrication process is the capability to embed target materials, including refractory metals, in the nanoparticle form into a host graphene matrix during target preparation. Finally, we fabricated nat Ir, nat Re, nat WO3, and nat HfO 2 nanoparticle-loaded graphene targets that can be used in nuclear physics research.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Decay spectroscopy of two-quasiparticle K isomers in Cm 246 , 248 via inelastic and transfer reactions

The decay of K isomers in Cm (Z = 96) isotopes has been investigated using inelastic and transfer reactions. The half-life of a previously identified 2-quasiparticle (qp) K π = 8⁻ isomer in 246 Cm has been measured. A new 2-qp isomer is observed in 248 Cm, its half-life measured and its decay scheme established. The reduced K hindrances extracted for the decay transitions from the isomers in 246,248 Cm suggest K to be a robust quantum number and validate axial symmetry in these nuclei. The excitation energies of the 2-qp isomers in 246 Cm (N = 150) and 248 Cm (N = 152) confirm the persistence of a deformed subshell gap at N = 152 in the Z ≈ 100 region down to Z = 96 nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗