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Work by Lawrence Livermore researchers has quelled debate surrounding the melting point for the transition metal tantalum. The June 24, 2021, Physical Review Letters paper notes that scientists had previously disagreed on whether tantalum experiences structural phase changes before melting. This work refines existing experimental techniques and shows that investigating thoroughly studied materials bolsters the scientific community’s confidence in obtained results.
Utilizing the Omega Laser Facility at the University of Rochester’s Laboratory for Laser Energetics (LLE), the team subjected tantalum samples to a series of increasingly powerful shockwaves, bringing the metal closer to a fully liquid state. Nanosecond x-ray diffraction, which avoids heating-induced chemical reactions, probed the sample’s interior and revealed the internal phase structure. The team found that tantalum, in fact, keeps its body-centered cubic formation until melting and that the melt curve at multimegabar pressures is steeper than previously thought.
“Our work provides improved physical information for how materials melt and respond at extreme conditions,” says Rick Kraus, the paper’s lead author. “Our findings increase understanding of how the iron cores of rocky planets solidify and improve predictions of materials experiments at the National Ignition Facility.” Livermore contributors included Dayne Fratanduono, Ray Smith, Amy Lazicki, Christopher Wehrenberg, and Jon Eggert, as well as LLE researchers J. Ryan Rygg and G. W. Collins.
Contact: Rick Kraus (925) 422-1454 (email@example.com).
The ongoing active reset research for linear induction accelerators is quickly progressing toward a functional x-ray movie technology—a new diagnostic capability to Lawrence Livermore. In a Laboratory first, the project’s Bipolar Research Experiment, a bipolar solid-state, pulsed-power system, accelerated (provided energy gain to) kiloamps of electron beam at Livermore’s Flash X-Ray (FXR) deep-penetration radiographic facility.
Accelerator physicist Nathaniel Pogue explains, “The objective is to produce 20 to 100 beam pulses, separated by tens to hundreds of nanoseconds. Each beam pulse creates a frame in a radiographic movie.” Such rapid timing is made possible by the newly added bipolar cells and solid-state pulsers along the FXR beamline. Between pulses, the cells quickly reenergize to accelerate the next beam pulse. Measurements confirmed that the cells transferred energy from the pulser to the beam, confirming the viability of both the hardware and methodology.
Pogue leads a multidisciplinary team working to finish the design, construction, and demonstration of a test injector, the Imperator. Once completed, the integrated system, which includes the bipolar solid-state, pulsed-power system, led by Katherine Velas, should be able to both produce and accelerate an electron beam. This capability will supply future hydrodynamics experiments with up to 10 times more image data than currently possible and provide more information with fewer experiments in support of the National Nuclear Security Administration’s Stockpile Stewardship Program.
Contact: Nathaniel Pogue (925) 422-9192 (firstname.lastname@example.org).
Nerve agents like sarin, venomous agent X, or Novichok block the transmission of messages from the brain and spinal cord or central nervous system (CNS) to the peripheral nervous system (PNS), which controls vital processes such as breathing and heart rate. Unfortunately, current nerve-agent antidotes only protect the PNS as they cannot cross the blood–brain barrier (BBB)—leaving the CNS vulnerable. Effective antidotes must be able to cross the BBB and use small molecule-based oximes that can efficiently restore acetylcholinesterase (AChE) activity—a crucial neurotransmission enzyme nerve agents target.
Scientists from Livermore’s Forensic Science Center (FSC) developed a promising and multifunctional antidote, LLNL-02, to counteract exposure to nerve-agent poisoning. LLNL-02 is a novel CNS-permeable oxime reactivator, making it the first antidote of its kind to achieve both BBB penetration and AChE reactivation.
To identify potential candidate compounds, researchers used computational modeling predictions and synthetic chemistry. The computational predictions were then validated with detailed in vitro and in vivo assays, and after two years, the team’s efforts led to the discovery of LLNL-02. FSC Director Audrey Williams says, “LLNL-02 is a promising, versatile compound that demonstrates a path forward for protecting against bioterrorism and chemical weapons.” The research, performed in conjunction with the U.S. Army Medical Research Institute of Chemical Defense, appeared in the July 30, 2021, issue of Scientific Reports.
Contact: Carlos Valdez (925) 423-1804 (email@example.com).