Livermore National Laboratory Research Articles

Nuclear-structure experiments at iThemba LABS to investigate discrepancies between (p, p′) and (γ, xn) data

The iThemba Laboratory for Accelerator Based Sciences (iThemba LABS) is a centre of expertise and innovation in the field of nuclear-structure physics and is a leader in several high-impact studies. One of the highlights of these nuclear-structure experiments is the study of the broad structure of the IsoVector Giant Dipole Resonance (IVGDR) in the rare-earth region. Proton inelastic scattering experiments with Ep = 200 MeV were performed on the even-even Nd isotope chain and 152Sm at very forward scattering angles including zero degrees with the K600 magnetic spectrometer. The evolution of the shape of the IVGDR in the transition from spherical to deformed nuclei was investigated. One of the goals of this highlighted study was to confirm the K-splitting observed in previous photo-absorption measurements from Saclay. Significant discrepancies were found between the direct (γ, xn) data obtained at Saclay and the equivalent photo-absorption cross sections obtained using (p, p′) data from the K600. Furthermore, discrepancies exist for several nuclei between photo-absorption data taken at the Saclay and Livermore laboratories. These discrepancies, possible reasons for them and future investigations will be presented and discussed.

Enabling Stable Li Metal Anodes for Solid-State Batteries

Solid-state batteries have the potential to transform energy storage by providing significantly higher energy densities and improved safety compared to conventional Li-ion batteries. However, robust high-capacity Li metal anodes are required to realize this technology. Current Li metal anode designs suffer from significant degradation over time due to non-uniform Li plating/stripping and loss of contact with the solid electrolyte during cycling. Carbon scaffold hosts have been shown to mitigate this problem in liquid electrolyte systems by creating a uniform electric field and providing abundant Li nucleation sites, but they have not been well explored in solid-state systems, which require the fabrication of more complicated mixed ion/electron conducting scaffolds to provide transport of both Li ions and electrons throughout the anode. We investigated the effect of scaffold architecture and chemistry on Li morphology and electrochemical performance using a combined experiment/theory approach. Scaffolds were characterized by SEM, Raman, and XPS before cycling in cells to evaluate their performance as hosts for Li plating/stripping. Atomistic and mesoscale modeling were used to help predict Li nucleation and current density hotspots and assist in guiding scaffold design. This work provides further insight into the relationship between anode design and Li metal cycling stability and will facilitate the development of safer, high-energy-density solid-state batteries.Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

10Be at iThemba LABS using a silicon nitride membrane stack as absorber for isobar suppression

10Be is an important isotope for accelerator mass spectrometry (AMS) because of the demand for cosmogenic radionuclide dating methods in the earth science and paleo-sciences community. At the iThemba Laboratory for Accelerator Based Science (iThemba LABS) we implemented full suppression of the interfering isobar 10B using a silicon nitride foil-stack, utilizing the 2+ charge state for high efficiency. We demonstrate the performance of this newly established AMS system using standards and test samples. We further present the results of an inter-comparison between iThemba LABS and the Center for Accelerator Mass Spectrometry/Lawrence Livermore National Laboratory, on AMS samples prepared from purified quartz at the University of Vermont. The results for 10Be from the laboratories are in close agreement, fully consistent with cross-calibration between them. AMS results for 26Al are in similarly good agreement, demonstrating the performance and accuracy of iThemba LABS for the most commonly measured in situ produced cosmogenic nuclides.

Exploring the Effect of Co-Sintering Conditions on the Chemistry and Microstructure of Solid Electrolyte/Cathode Interfaces in Solid-State Batteries

Solid-state batteries promise substantially higher energy densities and improved safety compared to traditional Li-ion batteries due to the replacement of flammable liquid electrolytes with more stable solid-state materials. These advantages make them excellent candidates for next-generation energy storage, but many processing and performance challenges must first be addressed. While several different types of solid electrolytes have been proposed, garnet-type materials such as Li6.4La3Zr1.4Ta0.6O12 (LLZTO) have attracted much interest due to their high ionic conductivities and good mechanical and electrochemical properties. However, they require high sintering temperatures for densification and are prone to poor contact and large interfacial resistance with cathode materials. Co-sintering the electrolyte and cathode together has been suggested as a strategy to improve this contact. However, the cathode degrades at a lower temperature than the electrolyte typically requires for sintering, making it challenging to achieve good contact without secondary phase formation. To determine the feasibility of this approach, we co-sintered LLZTO with two different cathode materials (LiNi0.6Mn0.2Co0.2O2 and LiCoO2) at several different temperatures. We assessed the associated structural changes and microstructure evolution using XRD, SEM, and TEM and explored how initial particle size, coatings, and sintering additives affect co-sintering outcomes. These results provide a more thorough understanding of the relationship between processing parameters, co-sintering conditions, and microstructure, which will enable the design of more optimized co-sintering approaches in the future.Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

In Memoriam: Mortimer L. Mendelsohn: (1 December, 1925-8 January, 2020).

In Memoriam: Mortimer L. Mendelsohn: (1 December, 1925-8 January, 2020).

Cats and llamas could offer a path to coronavirus therapies

Computation and experimentation also yield possible therapeutic compounds for COVID-19 [ABSTRACT FROM AUTHOR] Copyright of Physics Today is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use This abstract may be abridged No warranty is given about the accuracy of the copy Users should refer to the original published version of the material for the full abstract (Copyright applies to all Abstracts )

Peter and the Bomb: A Play

PETER, a man in his early thirties.JOSEPHINE, a woman in her late twenties. PETER's girlfriend.Josephine's bedroom. Livermore, CA. 1985. Night.A bedroom that overlooks a quiet street. The room's only furnishings are a nightstand holding a tall lamp, and a bed. In it, lay PETER and JOSEPHINE. The room is dark. There is no sound.When asked for his view on the value and nature of political theatre, in a 1985 interview with Benedict Nightingale, Pinter responded by reading a comment from Peter Hagelstein—a leading nuclear physicist: “My view of weapons has changed. Until 1980 or so, I did not want anything to do with nuclear anything. Back in those days, I thought there was something fundamentally evil about weapons. Now, I see it as an interesting physics problem.” Now, look, this man is really there. He is at the hilt. At the top of his profession. And what he is doing, and what he is encouraged to do … is to look at things as abstractions. That's how I understand his assertion. And that is what I think we are all encouraged to do. (Pinter 1985) Pinter, here, argues that it is the desired end of, ostensibly, a given nation-state to press its citizens to think abstractly. And his specific example, namely Hagelstein's portrayal of nuclear weapons as a science problem, underlines the dissonance between this object's true (according to Pinter) reality and its promoted abstraction.This glaring divide, and Pinter's interest in it, serves as the catalyst for my work. In my short drama, I offer a Pinteresque vision of Peter Hagelstein's relationship with his partner (in 1985) Josephine Stein, a notable dissident of his pioneering work in weapons research at Livermore National Laboratory.

Investigation of compression of indirect-drive targets under conditions of the NIF facility using one-dimensional modelling

The indirect compression dynamics of targets containing capsules with ablators of a plastic, high-density carbon and beryllium is simulated in the framework of a one-dimensional model based on the 1D RADIAN code. Experiments with such targets are performed on the NIF facility in the Livermore Laboratory (USA) in 2014 – 2018. The 1D simulation data are consistent with the results of experiments and calculations made at this Laboratory. The effect of the hard part of hohlraum radiation on capsule compression parameters is confirmed. We demonstrate the feasibility of eliminating this influence not only by selecting the hohlraum material but also by introducing admixtures into the capsule that absorb this radiation. It is shown how varying the amount of admixture in the capsule ablator varies the spectrum of the radiation that heats the DT fuel.

Superheavy elements

Synthesis of superheavy elements predicted by microscopic nuclear theory is investigated. The heaviest elements with Z = 114–118 were synthesized by fusion reactions of actinide nuclei with 48Ca ions accelerated using the U-400 complex at the Flerov Laboratory of Nuclear Reactions (FLNR), one of seven laboratories that comprise the Joint Institute for Nuclear Research (JINR) located in Dubna, Russia. The experiments were carried out in collaboration with physicists and chemists working at the Livermore and Oak Ridge national laboratories in located in California and Tennessee, respectively. Discovery of these elements allowed completion of the seventh period of the periodic table. The microscopic nuclear theory’s fundamental predictions about the possible existence of superheavy elements received the experimental confirmation. A new laboratory, i.e., the "STE Factory" associated with the JINR FLNR, has been established to research superheavy nuclei.

On the Problem of Thermonuclear Ignition and Burning in the NIF Laser: Ignition with Capsules Taking into Account the Influence of the Hohlraum Radiation on Implosion

One of the significant problems of modern physics is the creation and use of new energy sources. The decisive step in this direction is the realization of a positive yield in thermonuclear energy on a laboratory scale with the facilities that create and retain plasma. Between 2010 and 2017, a large series of experiments were performed at the National Ignition Facility laser at the Livermore Laboratory in the United States with the aim of achieving such a positive outcome. Until now, however, the ignition has not been reached. In this paper, for the first time the influence of the hohlraum radiation on capsule layers including a deuterium–tritium layer is discussed. It is shown that the negative influence of the ablator transparency can be compensated for by the selection of a capsule design with a greater optical thickness of the part of the ablator. This part of the ablator is not evaporated upon heating by an X-ray pulse. The design of such a capsule is proposed.

A >2-MJ, 1014-W laser system for DT fusion—NIF: a note in celebration of the 75th birthday of Prof. Theodore Haensch

In 1970, Dr. Theodore Haensch joined A.L. Schawlow’s group in the physics department at Stanford, as a NATO postdoctoral researcher. Within a short time, he and his colleagues had invented a new, high-resolution, tunable laser system using expanded reflection gratings and an N2 laser for pumping the fluorescing dyes. This work resulted in a high-brightness, high-repetition-rate, narrow-band laser probe for conducting optical spectroscopy at extreme levels of precision. Dr. Haensch, and his many colleagues, particularly Prof. Arthur Schawlow and their students at Stanford, then proceeded to revolutionize optical spectroscopy and to train several generations of exceptional young scientists. At the same time, the Siegman, Harris, and Byer laboratories also at Stanford were making major contributions to the laser and quantum electronics fields. Several students from both groups joined the Livermore Laboratory. That early work, and that of others, encouraged teams at the Lawrence Livermore National Laboratory to design and build a series of increasing complicated, high-power multi-beam laser systems to investigate the potential of laser fusion. The National Ignition Facility, recently completed, is enabling investigations of matter at very high temperatures, T > 1 million K and densities 100-1000× normal. In addition, researchers are creating 1015 DT fusion neutrons per fusion experiment and generating new knowledge about unusual and important conditions of matter.

L-shell electron excitations of Mg- through O-like tungsten ions

Electron impact excitations from ground state L shell viz. n = 2 → n = 3 transitions in Mg-like W62+, Na-like W63+, Ne-like W64+, F-like W65+ and O-like W66+ ions have been considered. A fully relativistic distorted wave (RDW) theory has been used to calculate the excitation cross-sections for an electric and magnetic dipole, as well as for the quadrupole transitions for these ions, which were observed recently in the measurements taken from an electron-beam-ion trap (EBIT-I) at the Livermore laboratory. We have performed calculations in the electron impact energy range from a threshold excitation energy of up to 60 keV. Our results, where possible, have been compared with the few previous theoretical calculations that are available. Analytic fits to our calculated excitation cross-sections have also been done for plasma modeling purposes. Our calculated cross-sections have been further employed to obtain the linear polarization of the photon emissions for dipole-allowed transitions due to the decay of the electron impact excited anisotropic states to the ground state for all five of the tungsten ions that are considered in the present work.

Seasonal and regional biases in CMIP5 precipitation simulations

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 60:35-50 (2014) - DOI: https://doi.org/10.3354/cr01221 Seasonal and regional biases in CMIP5 precipitation simulations Zhu Liu1, Ali Mehran1, Thomas J. Phillips2, Amir AghaKouchak1,* 1University of California Irvine, E4130 Engineering Gateway, Irvine, California 92697-2175, USA 2Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA *Corresponding author: amir.a@uci.edu ABSTRACT: This study provides insight into how CMIP5 climate models perform in simulating summer and winter precipitation at different geographical locations and climate conditions. Precipitation biases in the CMIP5 historical (1901 to 2005) simulations relative to the Climatic Research Unit (CRU) observations are evaluated over 8 regions exhibiting distinct seasonal hydroclimates: moist tropical (Amazonia and central Africa), monsoonal (southern China), moist continental (central Europe), semi-arid (western United States and eastern Australia), and polar (Siberia and Canada). While the bias and monthly quantile bias (MQB) reflect no substantial differences in CMIP5 summer and winter precipitation simulations at the global scale, strong seasonality and high inter-model variability are found over the selected moist tropical regions (i.e. Amazonia and central Africa). In the semi-arid regions, high inter-model precipitation variability is also displayed, especially in summer, while the median of simulations is an overestimate of both winter and summer precipitation. In Siberia and central Europe, most CMIP5 models underestimate summer precipitation, and overestimate it in winter. Also, the MQB values decrease as the choice of quantile thresholds increase, implying that the underestimation of summer precipitation is primarily associated with biases in lower quantiles of the precipitation distribution. While the CMIP5 models exhibit similar behaviors in simulating high-latitude winter precipitation, they differ substantially in summer simulations for the selected Canadian and Siberian regions. Finally, in the monsoonal southern China region, CMIP5 models exhibit large overall precipitation biases in both summer and winter, as well as at higher quantiles. KEY WORDS: Precipitation · Climate · CMIP5 Full text in pdf format Supplementary material PreviousNextCite this article as: Liu Z, Mehran A, Phillips TJ, AghaKouchak A (2014) Seasonal and regional biases in CMIP5 precipitation simulations. Clim Res 60:35-50. https://doi.org/10.3354/cr01221 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 60, No. 1. Online publication date: May 19, 2014 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2014 Inter-Research.

A New Skeletal Chemical Kinetic Mechanism of Ethanol Combustion for HCCI Engine Simulation

According to the detailed chemical kinetic mechanism of ethanol proposed by the U．S．Lawrence Livermore Laboratory, this paper analyzes the main approach of ethanol oxidation. Based on the detailed chemical kinetics mechanism, a skeletal chemical reaction mechanism is presented by reaction path analysis．Thus a simplified model is constructed, which consists of 26 species and 26 reactions．And then the comparative studies were given between the simplified model and the detailed model．The simulation results show that simplified model and detailed model have good consistency.

New Residents in the Majestic Icon of Science: The Periodic Table Filled in by New Elements

In the “Year of Chemistry,” 2011, the new chemical elements, Flerovium (Z = 114) and Livermorium (Z = 116), came to occupy their rightful position in the Periodic Table of the Chemical Elements. The IUPAC/IUPAP officially reported on 1 June 2011 that the Dubna-Livermore collaboration is credited with the discovery of these new superheavy elements. The elements were named in honor of Flerov Laboratory of Nuclear Reactions (Russia) and Livermore National Laboratory (USA). This suggestion of authors was approved recently.

Greek Fire: Nicholas Christofilos and the Astron Project in America’s Early Fusion Program

The Astron project, conducted from 1956 to1973 at Livermore National Laboratory, was the brainchild of Nicholas Christofilos, a Greek engineer with no formal physics credentials. Astron’s key innovation was the E-layer, a ring of relativistic electrons within a magnetic mirror device. Christofilos predicted that at sufficient E-layer density the net magnetic field inside the chamber would reverse, creating closed field lines necessary for improving plasma confinement. Although Astron never achieved field reversal, it left important legacies. As a cylindrical device designed to contain toroidal plasmas, it was the earliest conception of a compact torus, a class that includes the Spheromak and the FRC. The linear induction accelerator, developed to generate Astron`s E-layer, is now used in many applications. Through examination of internal lab reports and interviews with his colleagues and family, this research charts Christofilos’ career and places Astron in its historical context. This paper was originally prepared in 2004 as an undergraduate Junior Paper for the Princeton University History Department.

Study on Effective Average (γ, n) Cross Section for 89Y, 90Zr, 93Nb, and 133Cs and (γ, 3n) Cross Section for 99Tc

A nondestructive detection technique was proposed for the easy assessment of long-lived radionuclides by the use of bremsstrahlung photons. The nuclide of 99Tc was considered for the assessment over an effective average 99Tc (γ, 3n) 96Tc cross section. For validating the experimental method on 99Tc, photonuclear (γ, n) cross sections of 89Y, 90Zr, 93Nb, and 133Cs were measured. Continuous-energy bremsstralung photons were generated from a platinum target bombarded by an electron beam of 32/36MeV from an electron linac. The photonuclear (γ, n) cross sections were previously measured by Saclay (France) and Livermore (USA) laboratories for 89Y, 90Zr, 93Nb, and 133Cs nuclides. For 89Y, 90Zr, and 133Cs, the present results were in good agreement, within 9% deviation with Saclay and an acceptable deviation of 14–36% from Livermore. In the case of 93Nb, the contribution for 93Nb (γ, n) 92Nb* in the metastable state was 55.2% of the total (γ, n) cross section of Saclay in an averaged form. The present experimental method was thus confirmed to show a good accuracy. The effective average cross section of 99Tc (γ, 3n) 96Tc was obtained as 2.30 mb in the energy range of 25.723–36 MeV.

EUV emission spectra in collisions of multiply charged Sn ions with He and Xe

Extreme ultraviolet emission spectra of multiply charged Sn ions were measured in the wavelength range 5–38 nm, following electron capture into the excited states of slow Snq + (q = 5–21) ions passing through He and Xe gas targets. Identification of the transitions was carried out by comparison with calculations using the Hebrew University Livermore Laboratory Atomic physics Code. The target and the charge-state dependences of 4d–nℓ (nℓ = 4f, 5p and 5f) and 4p–4d transitions were observed.

Study on Effective Average (γ, n) Cross Section for 89Y, 90Zr, 93Nb, and 133Cs and (γ, 3n) Cross Section for 99Tc

A nondestructive detection technique was proposed for the easy assessment of long-lived radionuclides by the use of bremsstrahlung photons. The nuclide of 99Tc was considered for the assessment over an effective average 99Tc (γ, 3n) 96Tc cross section. For validating the experimental method on 99Tc, photonuclear (γ, n) cross sections of 89Y, 90Zr, 93Nb, and 133Cs were measured. Continuous-energy bremsstralung photons were generated from a platinum target bombarded by an electron beam of 32/36MeV from an electron linac. The photonuclear (γ, n) cross sections were previously measured by Saclay (France) and Livermore (USA) laboratories for 89Y, 90Zr, 93Nb, and 133Cs nuclides. For 89Y, 90Zr, and 133Cs, the present results were in good agreement, within 9% deviation with Saclay and an acceptable deviation of 14–36% from Livermore. In the case of 93Nb, the contribution for 93Nb (γ, n) 92Nb* in the metastable state was 55.2% of the total (γ, n) cross section of Saclay in an averaged form. The present experimenta...

Shock-wave compression of hydrogen isotopes condensed under megabar pressures

Experiments on shock wave compression of solid hydrogen (protium) up to 66 GPa and deuterium (in the initially liquid or solid phase) up to 123 GPa using spherical devices where a steel ball (impactor) is explosion-accelerated to 23 km/s are described. The experimental data are compared with those obtained by American researchers for liquid deuterium and protium, who used conventional explosives and light-gas guns as energy sources in the experiments carried out on the Z machine at Sandia National Labs, where an impactor was accelerated by an ultrahigh magnetic field, or on the NOVA laser at the Livermore National laboratory. Our data agree well with those derived by Sandia Labs.