Richard Post, a lifelong scientist who passed away on April 7, 2015, at age 96, joined Lawrence Livermore National Laboratory within weeks of its founding in 1952 and worked here for 63 years. Even after initially retiring in 1991, he continued his research, driven by a keen awareness of humankind’s need for clean, efficient energy.
Post pioneered the fusion-energy approach of using magnetic mirrors to confine the fusion reaction. His groundbreaking work on flywheels for energy storage—including seminal papers authored in the 1970s—established his reputation as the father of the modern flywheel for energy storage, envisioning flywheels made of lightweight composites and spinning at supersonic speeds in a vacuum chamber, magnetically suspended in a frictionless state.
Post’s many awards and honors include being among the first recipients of the American Physical Society’s James Clerk Maxwell Prize in 1978 and winning an R&D 100 Award in 2004 for his design of a magnetic levitation train. His name is on 34 patents—nine of which he obtained after the age of 90. Laboratory Director Bill Goldstein commented, “Dick Post is a legend. His unique contributions to the Lab have spanned its entire existence and enriched our place in history. It was an honor to have known him.”
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In a study published online in the March 30, 2015, edition of Nature Geoscience, researchers reported that carbon, delivered by comets or comet dust, is the “stealth” agent darkening Mercury’s surface—a mystery that had long puzzled planetary scientists in light of the planet’s low level of iron, an important darkening material in airless bodies such as the moon and asteroids.
Numerical calculations to assess the impact delivery of carbon on Mercury found that micrometeorites, which are mostly derived from carbon-enriched comets, would deliver enough carbon to affect observations of Mercury’s surface. These micrometeorites’ relatively low-impact velocities allow most material to be retained by the planet, resulting in surface carbon abundances of three to six percent, thereby darkening the planet.
“Understanding the role of micrometeorites in delivering dark material to Mercury provides new ways of interpreting observations of the planet,” says lead author Megan Bruck Syal, a postdoctoral researcher at Lawrence Livermore. “In addition, we are now working to understand how micrometeorites may have delivered other materials of interest to Mercury, including water.”
Hypervelocity impact experiments at NASA’s Ames Vertical Gun Range also tested whether carbon could be effectively entrained within glassy, impact-generated melt products, resulting in darker spectral signatures. The results were consistent with remote sensing observations of Mercury by the MESSENGER mission, further suggesting an important role for carbon on Mercury’s surface.
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Ultrathin mounting membranes for inertial confinement fusion targets used at the National Ignition Facility (NIF) consist of two plastic membranes holding the target capsule at the center of the hohlraum. The membranes, called tents, were originally estimated to have an acceptable effect on implosion. However, results from a systematic study published in the February 4, 2015, edition of Physics of Plasma showed that in low-adiabat implosions, the tent seeds a perturbation that induces Rayleigh–Taylor hydrodynamic instabilities, affecting symmetry and thereby reducing the implosion’s yield.
The researchers used x-ray area–backlit imaging to assess in-flight, low-mode, two-dimensional asymmetries of the shell. The time-resolved images revealed features that can be related to the liftoff position of the tent membranes.
The experimental data suggest that in the implosions, the tents seed hydrodynamic instabilities at the capsule surface from the beginning, which grow throughout the implosion until they eventually come close to perforating the capsule. On the other hand, in higher adiabat shots the tent’s impact is significantly less because of lower overall hydrodynamic instability in the implosion.
“This work,” the researchers say, “shows that it is important to use mounting membranes that are as thin as possible. We need to find mitigation strategies, for example, in the form of the laser pulse shapes for less instability growth or in alternative mounting strategies.”
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