August 10, 2016
International scientists have identified the dynamics of the core of one of the most massive objects in the known universe, bringing insight into the cosmology of clusters of galaxies.
The Hitomi collaboration, in which Physical and Life Science scientist Greg Brown is a member, found that the turbulent motion of the intracluster gas in the Perseus cluster is only a small fraction of the mechanism responsible for heating the gas to 50 million degrees Kelvin. The Perseus cluster is a groupr of galaxies in the constellation Perseus. It is one of the most massive objects in the known universe, containing thousands of galaxies immersed in a vast cloud of multimillion degree gas.
This finding, published in the July 6 edition of Nature, demonstrates that it is possible to infer an accurate mass of a cluster almost exclusively from its thermal hydrostatic pressure without having to rely on low accuracy measurements and estimates of the turbulent pressure of the system. Accurate cluster masses provide strong constraints on cluster cosmology and dark matter.
April 15, 2016
Hydrogen is the most abundant element found in the universe, making up nearly three-quarters of all matter. Despite its prevalence, questions about the element remain.
In a new paper published April 15th by Nature Communications, a team of researchers, including scientists from Lawrence Livermore National Laboratory (LLNL), aims to answer one of those questions – what happens to hydrogen at high pressure.
"This research tells us something about the process of hydrogen's transformation from insulator to metal at high pressure," said lead author Paul Davis. Davis conducted this research while working as a University of California, Berkeley graduate student sited within LLNL's National Ignition Facility & Photon Science Directorate in the former group of Siegfried Glenzer (now a professor at Stanford/SLAC National Accelerator Laboratory). Paul Davis now serves as a science and technology policy fellow at the Department of Defense.
"Because it's hard to do these kinds of high pressure experiments, there tends to be more theoretical and computational work than data available. In particular, no one has been able to do detailed X-ray scattering studies at a range of pressures before," he said. "This work helps us confirm theoretical models for materials under extreme conditions."
April 13, 2016
Beginning in the 19th century, scientists developed equations of state (EoS) to describe how material properties such as volume or internal energy are affected by intensive pressure or temperature. Experiments are conducted to determine the volume a sample occupies at various pressure-temperature conditions. But what happens when a suitable experimental technique does not exist or is prohibitively expensive?
Create a new experimental technique. In new research, Lawrence Livermore scientists did just that, using lights and a camera to make direct volume measurements in small-scale highly pressurized crystals to determine the equation of state of a special material.
"In order to accurately predict performance characteristics for an important Department of Defense material, we needed to know its equation of state," said Sorin Bastea, an LLNL computational physicist and project leader. "Normally our team of experimentalists conducts high-pressure X-ray diffraction measurements, sound-speed measurements or ultrafast tabletop shock compression studies to determine pressure-dependent sample volumes."
Unfortunately the material, α-NTO (an insensitive energetic material), has an extraordinarily complicated crystal structure and limits conclusive volume determinations from high pressure X-ray diffraction (XRD) data. After one year, national lab and academic teams were unable to physically prepare α-NTO for small-scale shockwave EoS or sound-speed diagnostic measurements.
January 28, 2016
Fast ignition (FI) is an alternative approach to conventional inertial confinement fusion that involves separating the compression and heating phases of the implosion, using a more stable compression followed by a short burst of localized heating. By separating these two aspects, the fuel can be compressed isochorically (without a central hotspot), reducing the fuel density requirements or increasing the mass of fuel that can be compressed and potentially leading to higher gain. The heating pulse in electron FI is generated by a separate short-pulse petawatt (quadrillion-watt) laser that creates an intense, MeV (million-electron-volt) electron beam that deposits its energy into the compressed core.
Fast ignition requires efficient heating of pre-compressed high-density fuel by an intense relativistic electron beam produced from laser–matter interaction. Understanding the details of electron-beam generation and transport is crucial for FI.
In a paper published in the Jan. 11 issue of Nature Physics, an international team of researchers reported on the first visualization of fast electron spatial energy deposition in a laser-compressed cone-in-shell FI target. Led by Farhat Beg and Charlie Jarrott of UC San Diego and Mingsheng Wei of General Atomics, the team included LLNL scientists Hui Chen, Tilo Döppner, Mike Key, Harry McLean and Prav Patel. The research was facilitated by doping the shell with copper and imaging the K-shell X-ray radiation (the K shell is the electron orbit closest to the nucleus). The experiments were conducted at the OMEGA Laser Facility at the University of Rochester's Laboratory for Laser Energetics (LLE) as part of the National Laser Users Facility program that provides academic access to the LLE facilities for basic science research.
September 23, 2015
A National Ignition Facility (NIF) experimental campaign may have unlocked scientific secrets behind how hydrogen becomes metallic at high pressure.
"Hydrogen properties are still puzzling," said Lawrence Livermore National Laboratory (LLNL) physicist Marius Millot. "In particular, back in 1935, it was predicted that hydrogen should become metallic at sufficiently high pressure. But, using static compression, our colleagues have yet to find clear evidence for metallization at room temperature."
In previous studies spanning a decade at the OMEGA Laser Facility at the University of Rochester, the team probed shock-compressed hydrogen properties at temperatures ranging from 3,000 to 50,000 Kelvin to reveal the role of temperature in hydrogen molecule dissociation and the progressive metallization in the warm dense fluid.
August 31, 2015
Astronomers have found evidence for a faded electron cloud "coming back to life," much like the mythical phoenix, after two galaxy clusters collided.
This "radio phoenix," so-called because the high-energy electrons radiate primarily at radio frequencies, is found in Abell 1033. The system is located about 1.6 billion light years from Earth.
By combining data from NASA's Chandra X-ray Observatory (link is external), the Westerbork Synthesis Radio Telescope (link is external) in the Netherlands, NSF's Karl Jansky Very Large Array (link is external) (VLA) and the Sloan Digital Sky Survey (link is external) (SDSS), astronomers were able to re-create the scientific account behind the cosmic story of the radio phoenix.
Galaxy clusters are the largest structures in the universe held together by gravity. They consist of hundreds or even thousands of individual galaxies, unseen dark matter and huge reservoirs of hot gas that glow in X-ray light. Understanding how clusters grow is critical to tracking how the universe evolves over time.
Lawrence Livermore scientist Will Dawson mapped the galaxy distribution and performed the merger dynamics analysis. "This provided evidence that we were dealing with a major cluster merger (i.e., a merger between two large and relatively equal mass galaxy clusters) capable of generating a plasma shock, which could awaken the radio phoenix," Dawson said.
Astronomers think that the supermassive black hole close to the center of Abell 1033 erupted in the past. Streams of high-energy electrons filled a region hundreds of thousands of light years across and produced a cloud of bright radio emission. This cloud faded over a period of millions of years as the electrons lost energy and the cloud expanded.
August 13, 2015
For the first time, Lawrence Livermore scientists, as part of an international team, have discovered the most Jupiter-like planet ever seen in a young star system, lending clues to understanding how planets formed around our sun.
Using a new advanced adaptive optics device on the Gemini Planet Imager (link is external) (GPI) on the Gemini South Telescope in Chile, the team took an image of the planet, which is about twice the size of Jupiter.
Called 51 Eridani b, the planet is the first in a wave of discoveries by a new generation of planet-hunting instruments, and could help scientists unlock the secrets of how Jupiter and other gas giants form and shape their planetary systems. It is a million times fainter than its star and shows the strongest methane signature ever detected on an alien planet, which should yield additional clues as to how the planet formed.
May 26, 2015
Using ever more energetic lasers, Lawrence Livermore researchers have produced a record high number of electron-positron pairs, opening exciting opportunities to study extreme astrophysical processes, such as black holes and gamma-ray bursts.
By performing experiments using three laser systems — Titan at Lawrence Livermore, Omega-EP at the Laboratory for Laser Energetics and Orion at Atomic Weapons Establishment (AWE) in the United Kingdom — PLS physicist Hui Chen and her colleagues created nearly a trillion positrons (also known as antimatter particles). In previous experiments at the Titan laser in 2008, Chen's team had created billions of positrons.
Positrons, or "anti-electrons," are anti-particles with the same mass as an electron but with opposite charge. The generation of energetic electron-positron pairs is common in extreme astrophysical environments associated with the rapid collapse of stars and formation of black holes. These pairs eventually radiate their energy, producing extremely bright bursts of gamma rays. Gamma-ray bursts (GRBs) are the brightest electromagnetic events known to occur in the universe and can last from ten milliseconds to several minutes. The mechanism of how these GRBs are produced is still a mystery.
May 7, 2015
New results from the NASA NuSTAR telescope show that a supernova close to our galaxy experienced a single-sided explosion.
A team of scientists, including co-author Michael Pivovaroff of Physical and Life Sciences Physics Division, found that X-ray emissions taken with the Nuclear Spectroscopic Telescope Array (NuSTAR) show that the Supernova 1987A explosion was highly asymmetric. The results appear in the May 8 edition of the journal, Science.
NuSTAR observations, including those of 1987A, provide strong and compelling observational evidence that supernovae are not symmetric.
Supernova 1987A in the Large Magellanic Cloud provides a unique opportunity to study a nearby (170,000 light years) core collapse supernova explosion (CCSN) and its subsequent evolution into a supernova remnant.
SN1987A has validated some basic scientific assumptions about CCSNs. A neutrino flash confirmed that the overall explosion is driven by the collapse of the central core to a neutron star. Direct gamma-ray detection of cobalt isotopes and the correlation between the exponential decay of the optical light curve and lifetime of these isotopes confirmed that the light curve is powered by radioactive decay.
"Even with all we have previously learned about SN1987A, NuSTAR has taught us some new things," said Pivovaroff. "Our observations confirmed the tremendous speeds at which the exploding material is moving and helped us constrain geometrical models that show just how lopsided the supernova explosion was."
In core-collapse supernovae, an isotope of titanium (⁴⁴ Ti) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed remnant. The radioactive decay of this isotope provides a direct probe of the supernova engine. NuSTAR measurements confirm that heavy elements are moving at speeds of about 3,000 kilometers per second, several times higher than expected from spherically symmetric models.
April 29, 2015
The new Kirkpatrick-Baez Optic (KBO) diagnostic is needed to obtain high-resolution images of the "hot spots" at the center of target capsules during NIF inertial confinement fusion (ICF) implosions, explained PLS physicist Louisa Pickworth, the project's lead scientist. Kirkpatrick-Baez optics — two curved "grazing incidence" mirrors positioned at right angles to form a two-dimensional X-ray image — is a widely used technology. "They work very nicely," said Tommaso Pardini of the PLS X-ray Optics Group. "The interesting thing about this project is that we incorporated this vintage technology into a very difficult environment, which is NIF."
Development of the KBO diagnostic was a collaboration between NIF & Photon Science and the Physical and Life Sciences (PLS) Directorate. One PLS team developed special multilayer coatings for the KBO system's mirrors. "One thing that Livermore does very well is coating X-ray optics with these multilayers," Pardini said. "Chris Walton, Paul Mirkarimi, Jennifer Alameda and Regina Soufli spent quite a bit of time developing coating that would fit the requirements." Experimental flexibility will be provided by swapping mirror packs with different energy responses.
April 24, 2015
Galaxies are often found in clusters, which contain many "red and dead" members that stopped forming stars in the distant past. Now an international team of astronomers, including Will Dawson of the Physics Division of the Physical and Life Sciences directorate of LLNL, has discovered that these comatose galaxies can sometimes come back to life. If clusters of galaxies merge, a huge shock wave can drive the birth of a new generation of stars — the sleeping galaxies get a new lease on life.
March 2, 2015
Violent collisions between the growing Earth and other objects in the solar system generated significant amounts of iron vapor, according to a new study by LLNL scientist Richard Kraus and colleagues.
October 17, 2014
Personal electronics such as cell phones and laptops could get a boost from some of the lightest materials in the world.
Lawrence Livermore researchers have turned to graphene aerogel for enhanced electrical energy storage that eventually could be used to smooth out power fluctuations in the energy grid.
December 17, 2014
The deaths of stars are not as final as they seem. These often-violent events give rise to exotic stellar remnants that are dispersed throughout the cosmos. Neutron stars, for example, are created when very massive stars (those with a mass between 10 and 30 times that of our Sun) exhaust their supply of nuclear fuel and die in supernovae explosions.
November 6, 2014
The noble gas xenon should be found in terrestrial and Martian atmospheres, but researchers have had a hard time finding it.
The prevailing theory claims that due to xenon's weight—it is a heavy gas—it could be trapped in a planet's core or in the mantle during the planet's formation.
Lawrence Livermore scientists and collaborators have discovered that the xenon can be trapped in the subsurface of the Earth, shedding new insights into the long-standing mysteries of the "missing xenon" in earth science.
October 14, 2014
In a recent article published in the Review of Scientific Instruments, a research team led by scientists at Lawrence Livermore National Laboratory describe a technique for 3D-image processing of a high-speed photograph of a target, "freezing" its motion and revealing hidden secrets.
July 17, 2014
Lawrence Livermore scientists for the first time have experimentally re-created the conditions that exist deep inside giant planets, such as Jupiter, Uranus and many of the planets recently discovered outside our solar system.
February 19, 2014
For the first time, an international team of astrophysicists, including Lawrence Livermore National Laboratory scientists, have unraveled how stars blow up in supernova explosions.