A5031954066- Nuclear physics research studies
- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
- Quantum Chromodynamics and Particle Interactions
- Astronomical and nuclear sciences
- Advanced NMR Techniques and Applications
- Nuclear Materials and Properties
- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Radiation Detection and Scintillator Technologies
- Radiopharmaceutical Chemistry and Applications
- Radiation Therapy and Dosimetry
- Medical Imaging Techniques and Applications
- Quantum chaos and dynamical systems
- Particle physics theoretical and experimental studies
- Radioactive element chemistry and processing
- Rare-earth and actinide compounds
- Gamma-ray bursts and supernovae
- Cold Fusion and Nuclear Reactions
- Electron and X-Ray Spectroscopy Techniques
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Graphite, nuclear technology, radiation studies
Lawrence Livermore National Laboratory
2015-2024
San Diego State University
2023
The London College
2022
Massachusetts Institute of Technology
2022
Technical University of Denmark
2022
Lawrence Berkeley National Laboratory
2011
Institute of Materials and Environmental Chemistry
2011
Charles University
2011
Seoul National University
2011
Physical Sciences (United States)
2010
Nuclear reaction cross sections are important for a variety of applications in the areas astrophysics, nuclear energy, and national security. When these cannot be measured directly or predicted reliably, it becomes necessary to develop indirect methods determining relevant rates. The surrogate reactions approach is such an method. First used 1970s estimating $(n,f)$ sections, method has recently been recognized as potentially powerful tool wide range that involve compound-nuclear reactions....
Abstract We review recent progress and motivate the need for further developments in nuclear optical potentials that are widely used theoretical analysis of nucleon elastic scattering reaction cross sections. In regions chart away from stability, which represent a frontier science over coming decade will be probed at new rare-isotope beam facilities worldwide, there is targeted to quantify reduce model uncertainties, especially with respect potentials. first describe primary physics...
Optical-model potentials (OMPs) continue to play a key role in nuclear reaction calculations. However, the uncertainty of phenomenological OMPs widespread use---inherent any parametric model trained on data---has not been fully characterized, and its impact downstream users remains unclear. Here we assign well-calibrated uncertainties for two representative global OMPs, those Koning-Delaroche Chapel Hill '89, using Markov-chain Monte Carlo parameter inference. By comparing canonical versions...
Obtaining reliable data for nuclear reactions on unstable isotopes remains an extremely important task and a formidable challenge. Neutron capture cross sections---crucial ingredients models of astrophysical processes, national security applications, simulations energy generation---are particularly elusive, as both projectile target in the reaction are unstable. We demonstrate new method determining sections neutron isotopes, using $^{87}\mathrm{Y}(n,\ensuremath{\gamma})$ prototype. To...
The neutron-capture reaction plays a critical role in the synthesis of elements stars and is important for societal applications including nuclear power generation stockpile-stewardship science. However, it difficult-if not impossible-to directly measure neutron capture cross sections exotic, short-lived nuclei that participate these processes. In this Letter we demonstrate new technique which can be used to indirectly determine exotic systems. This makes use (d,p) transfer reaction, has...
The validity of the surrogate ratio method for determining ($n,f$) cross sections actinide nuclei is examined. This relates two compound-nucleus reaction to a coincidence events from measurements in which same compound are formed via direct reaction. With certain assumptions, allows one be inferred if other known. We develop nuclear reaction-model simulation investigate whether assumptions underlying approach valid and employ these simulations assess obtained indirectly by applying analysis...
Motivated by the renewed interest in surrogate nuclear reactions approach, an indirect method for determining compound-nuclear reaction cross sections, prospects ($n,\ensuremath{\gamma}$) sections deformed rare-earth and actinide nuclei are investigated. A model is employed to simulate physical quantities that typically measured experiments used assess validity of Weisskopf-Ewing ratio approximations, which analysis reactions. The expected accuracy extracted from typical measurements...
Electric dipole strength near the neutron separation energy significantly impacts nuclear structure properties and astrophysical scenarios. These excitations are complex in nature may involve so-called pygmy resonance (PDR). Transition densities play a crucial role understanding of excited states, including collective excitations, as well constructing transition potentials DWBA or coupled-channels equations. In this work, we focus on electric spherical molybdenum isotopes, particularly...
Cross sections for compound-nuclear (CN) reactions are important nuclear astrophysics and other applications. Direct measurements not always possible the of interest calculations without experimental constraints can be quite uncertain. Thus indirect approaches, such as surrogate reaction method (SRM), being developed to fill gaps. The SRM, which uses a (direct) inelastic scattering or transfer obtain information on decay specific compound nucleus, has long history providing probabilities...
Porter-Thomas fluctuations of neutron widths skew compound nuclear decay probabilities from their statistical Hauser-Feshbach values. We present a straightforward method to correct calculations for these fluctuations, useful modeling near-threshold competition between gamma and emission following beta or when standard width fluctuation corrections are inadequate.
The past couple of decades have seen tremendous advances in nuclear structure and reaction theory. Innovative theory frameworks for describing the many-body system, increasingly powerful computers, opportunities confronting predictions with data on unstable nuclei, been driving field. An important goal is to move from phenomenological ingredients calculations predictive theories based microscopic frameworks. We discuss ongoing efforts aimed at integrating descriptions into medium-mass heavy...
Phenomenological optical-model potentials (OMPs) are a key ingredient for nuclear cross section libraries that enter astrophysical nucleosynthesis simulations. While existing OMPs can reliably reproduce direct reaction sections on β-stable targets, the lack of scattering data β-unstable targets limits credibility extrapolated to extremely neutron-rich regime reached during explosive nucleosynthesis. Recent work with fully non-local dispersive indicates even in regions where unavailable,...
Electric dipole strength near the neutron separation energy significantly impacts nuclear structure properties and astrophysical scenarios. These excitations are complex in nature may involve so-called pygmy resonance (PDR). Transition densities play a crucial role understanding of excited states, including collective excitations, as well constructing transition potentials DWBA or coupled-channels equations. In this work, we focus on electric spherical molybdenum isotopes, particularly 96...
We have deduced the cross section for $^{237}\mathrm{U}$($n,f$) over an equivalent neutron energy range from 0 to 20 MeV using surrogate ratio method. A 55 $^{4}\mathrm{He}$ beam 88 inch cyclotron at Lawrence Berkeley National Laboratory was used induce fission in following reactions: $^{238}\mathrm{U}$$(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$ and $^{236}\mathrm{U}$$(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$. The $^{238}\mathrm{U}$ reaction a...
The surrogate nuclear reaction method can be used to determine neutron-induced cross sections from measured decay properties of a compound nucleus created using different and calculated formation sections. reliability $(n,\ensuremath{\gamma})$ determined the Weisskopf-Ewing ratio approximations are explored for $^{155,157}\mathrm{Gd}$$(n,\ensuremath{\gamma})$ reactions. Enriched gadolinium targets were bombarded with 22-MeV protons $\ensuremath{\gamma}$ rays detected in coincidence scattered...
We introduce a new framework for studying clustering and calculating alpha partial widths using ab initio wave functions. demonstrate the formalism $^{20}$Ne, by overlap between $^{16}$O$+\alpha$ cluster configuration states in $^{20}$Ne computed symmetry-adapted no-core shell model. present spectroscopic amplitudes factors, compare those to symplectic shell-model results larger model spaces, gain insight into underlying physics that drives alpha-clustering. Specifically, we report on width...
Developing a predictive capability for inelastic scattering will find applications in multiple areas. Experimental data neutron-nucleus is limited and thus one needs robust theoretical framework to complement it. Charged-particle can be used as surrogate $(n, \gamma)$ reactions predict capture cross sections unstable nuclei. Our work uses microscopic nuclear structure calculations spherical nuclei obtain nucleon-nucleus potentials calculate these processes. We implement the Jeukenne,...
A fermion realization of the nuclear Sp(6,R) model, which complements traditional bosonic representation, is developed. recursive process presented in symplectic matrix elements arbitrary one-body operators between states excitation Nℏω and N′ℏω same or different bands are related back to valence shell elements, can be evaluated by standard model techniques. Matrix so determined may used calculate observables such as electron scattering form factors carry detailed structural information on...
The neutron-induced fission cross section of $^{238}\mathrm{Pu}$ was determined using the surrogate ratio method. $(n,f)$ over an equivalent neutron energy range 5--20 MeV deduced from inelastic $\ensuremath{\alpha}$-induced reactions on $^{239}\mathrm{Pu}$, with $^{235}\mathrm{U}$($\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$ and $^{236}\mathrm{U}$($\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$ used as references. These reference reflect...
Indirect methods play an important role in the determination of nuclear reaction cross sections that are hard to measure directly. In this paper we investigate feasibility using so-called surrogate method extract neutron capture for low-energy compound-nuclear reactions spherical and near-spherical nuclei. We present develop a statistical simulation explore different approaches utilizing data. assess success each approach by comparing extracted with predetermined benchmark. particular,...
In the Surrogate Method, measured decay probability of a compound nucleus formed via direct reaction is used to extract cross section for with different entrance channel that proceeds through same nucleus. An extension Ratio Method (SRM), uses ratio probabilities infer an unknown relative known one. To test SRM we compare direct-reaction-induced fission $^{234}\mathrm{U}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{'}f)$ $^{236}\mathrm{U}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{'}f)$...