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NEWS | Dec. 9, 2014

Dr. Alexander Velikovich Receives Sigma Xi Award for Pure Science

By Daniel Parry

U.S. Naval Research Laboratory (NRL) plasma physicist, Dr. Alexander L. Velikovich is awarded the 2014 NRL-Edison Sigma Xi Award for Pure Science for outstanding contributions to the studies of perturbation evolution and instability mitigation in Z pinch systems and laser plasma targets.

The Z-pinch is an application of the Ampére force—a magnetic force acting upon a linear current—whereas particles in current-carrying plasma are pulled toward each other by the Ampére force, thus increasing gas pressure of the plasma.

Dr. Velikovich's contributions to Z-pinch instability mitigation led to significant increases in x-ray radiation and neutron yields used for testing stockpile components by departments of Defense and Energy, said Dr. Thomas Mehlhorn, superintendent, Plasma Physics Division. His research at NRL has enabled pioneering experimental work on the laboratory's Nike laser and has greatly contributed to research in the areas of high energy density physics and applications to inertial confinement fusion.

Beginning at NRL in 1999, the focus of Velikovich's research has pertained to High Energy Density Physics (HEDP) and Inertial Confinement Fusion (ICF), particularly to laser-fusion and Z-pinch-related plasma hydrodynamics. His results on stabilization of Rayleigh-Taylor (RT) instability in Z-pinch plasmas by the 'snowplow' mechanism and density tailoring formed the theoretical basis for x-ray generation in Z-pinch plasma radiation sources.

His research translated into the development of a theory that provided the physical basis for most hydrodynamic experiments done on the Nike krypton fluoride (KrF) laser at NRL over the past decade. Participating in the design, modeling and interpretation of these results, Velikovich's discoveries were instrumental in establishing the physical picture of the RT instability seeding in laser fusion targets caused by the roughness of the front and rear surface of a laser target.

Velikovich is also the developer of the first analytical theory to calculate the time-dependent growth of compressible Richtmyer-Meshkov (RM) instability in the linear regime, and a non-linear RM theory that explained reduction of its growth rate for large initial amplitude. Results were observed in experiments on both the Nova laser at Livermore National Laboratory and on the Omega laser at the Laboratory for Laser Energetics (LLE).

Many physical effects, such as ablative RM instability, areal mass oscillations in laser targets due to strong shock interaction with a rippled rear surface, oscillations in an unsupported shock wave propagating through a laser target, and production of jets from the ripples at the rear surface had been first observed on Nike, and then reproduced in other laboratories including LLE.

Velikovich earned a Master of Science equivalent degree in physics awarded by Moscow State University Department of Physics, Moscow, Russia, in 1974, and in 1978 received a Ph.D. equivalent degree in plasma physics and chemistry awarded by Kapitza Institute for Physical Problems, U.S.S.R. Academy of Sciences. In 1991 he earned an Advanced Degree of Doctor of Science (equivalent of Habilitation in European Union countries) in Electrophysics awarded by High Current Electronics Institute, Russian Academy of Sciences, Tomsk, Russia.

In 2005 Velikovich was elected Fellow of the American Physical Society upon the recommendation of its Division of Plasma Physics for outstanding contributions to the theories of dynamics and stability of Z-pinch plasmas, Richtmyer-Meshkov instability and related effects of early-time perturbation seeding and evolution in laser plasma targets. In 2010, along with colleagues from Sandia and NRL, Velikovich shared the 2010 Department of Energy (DoE) Defense Programs Award of Excellence for increased cold x-ray source yields, improved source characterization and debris mitigation techniques to qualify stockpile components on refurbished Z machine. In 2000, 2007, 2010, and 2012, he was the recipient of the NRL Alan Berman Research Publication Award.

Author and co-author of more than 170 publications in leading peer-reviewed journals on plasma physics, hydrodynamics, shock waves, nonlinear optics and quantum electronics, with over 2,500 citations, Velikovich has contributed greatly to the studies of hydrodynamics instability seeding and development in Z-pinch loads and laser targets. Most recently he has developed a theory explaining the effect of shock-generated turbulence, which was discovered in numerical simulations at NRL over a decade ago, on the Rankine-Hugoniot jump conditions—derived from laws of mass, momentum, and energy.

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