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Aglitskiy Y.,SAIC | Velikovich A.L.,Plasma Physics Division | Karasik M.,Plasma Physics Division | Metzler N.,ARTEP Inc | And 8 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2010

In inertial confinement fusion (ICF), the possibility of ignition or high energy gain is largely determined by our ability to control the Rayleigh-Taylor (RT) instability growth in the target. The exponentially amplified RT perturbation eigenmodes are formed from all sources of the target and radiation non-uniformity in a process called seeding. This process involves a variety of physical mechanisms that are somewhat similar to the classical Richtmyer-Meshkov (RM) instability (in particular, most of them are active in the absence of acceleration), but differ from it in many ways. In the last decade, radiographic diagnostic techniques have been developed that made direct observations of the RM-type effects in the ICF-relevant conditions possible. New experiments stimulated the advancement of the theory of the RM-type processes. The progress in the experimental and theoretical studies of such phenomena as ablative RM instability, re-shock of the RM-unstable interface, feedout and perturbation development associated with impulsive loading is reviewed. © 2010 The Royal Society. Source


News Article
Site: http://www.nrl.navy.mil/media/news-releases/

Dr. Ira Schwartz, head of the Nonlinear System Dynamics Section in the Beam Physics Branch, Plasma Physics Division at the U.S. Naval Research Laboratory (NRL), has been elected Fellow of the American Physical Society (APS). Schwartz is recognized by the APS for his pioneering contributions to the understanding and development of topological insights into the dynamics, fluctuations, and control of strongly nonlinear physical and population systems. Well known for his fundamental and extensive contributions to the theory of nonlinear dynamical systems, Schwartz's innovative work has stimulated many new experiments in a variety of fields as well as further theoretical research. "His theory combines deep mathematical insight and sophisticated novel techniques with detailed understanding of the underlying physics," says colleague Mark Dykman, professor, Michigan State University. "He pioneered the application of feedback techniques to enable the stabilization of unstable states in chaotic systems over a wide parameter range. This technique is quite general and allows accessing to hard to reach dynamical regimes." Schwartz has developed theoretical tools and topological insight into the effect of driving for a broad class of nonlinear systems, which can display chaotic bursting. The results explained the nontrivial behavior of such systems with varying parameters, including switching between dynamical chaos and periodic stable states. They have been used in laser physics, theory of Josephson junction arrays, and found numerous applications in population dynamics such as epidemic outbreaks and their suppression. A fundamentally important and novel contribution made by Schwartz is in the theory of stochastic phenomena in dynamical systems, in particular, the topological approach to the problem of spontaneous extinction in population dynamics and in other discrete-variable physical and chemical systems. This general approach has been extended by Schwartz and used in analyzing fluctuations and extinction in adaptive networks, which has recently led to new methods of controlled disease eradication in large populations. Moreover, Schwartz has shown how social behavior works in conjunction with treatment policy, and has opened new areas of network analysis. Schwartz holds a Bachelor of Science in physics from the University of Hartford (1973), a master's in physics from the University of Connecticut (1975) and a Ph.D. in applied mathematics from the University of Maryland (1980). He began his career at NRL in 1983 in the Optical Sciences Division, and at present is head of the Nonlinear System Dynamics Section. He is inventor and co-inventor of six patents, most recently robotic tracking of Lagrangian Coherent Structures, and of the over 100 archival papers he has published, Schwartz and co-authors have published 11 Physical Review Letters for the APS. Schwartz has mentored many post doctoral Fellows, graduate and undergraduate students in the nonlinear sciences, has been the invited lecturer at more than 20 major physics and applied mathematics symposiums, and has been awarded more than 10 meritorious citations given by the U.S. Navy and the APS. The APS is a non-profit membership organization working to advance and diffuse the knowledge of physics. APS Fellows are elected on the criterion of exceptional contributions to the physics enterprise that are comprised of outstanding physics research, important applications of physics, leadership in or service to physics, or significant contributions to physics education. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.


News Article
Site: http://www.nrl.navy.mil/media/news-releases/

Dr. Arati Dasgupta from the U.S. Naval Research Laboratory's (NRL's) Radiation Hydrodynamics Branch of the Plasma Physics Division was recently awarded fellowship to the Washington Academy of Sciences. She is recognized for "outstanding achievements and contributions in the field of plasma physics." In order to recognize scientific work of merit and distinction, the Washington Academy of Sciences awards fellowships annually to scientists who work in the greater Washington D.C. area. To become a fellow, a person must be nominated by two Fellows of the Academy, one of whom must be familiar with the applicant's work. Election to fellowship is by vote of the Board of Managers upon recommendation of the Committee on Membership. Dr. Dasgupta was sponsored by Dr. Katherine Gebbie, director of Physics Laboratory at the National Institute of Science and Technology (NIST) and was co-sponsored by Dr. Charles Clark, chief of Electron and Optical Division at NIST and Program manager of Atomic and Molecular Physics at the Office of Naval Research (ONR). Dr. Dasgupta has made outstanding and enabling contributions in a very broad spectrum of activities in the areas of basic and applied atomic physics. Since arriving at NRL, Dr. Dasgupta's research has lead to improved understanding of the important atomic processes relevant to Z-pinch plasma radiation sources, which are laboratory sources of intense x-rays. Her most important contributions in this investigation are detailed calculations of the ionization structure and the radiation generated in the Z facility at the Sandia National Laboratories. Dr. Dasgupta's essential contribution to the success of this radiation-source development program has been widely recognized. Dr. Dasgupta is widely known for highly accurate calculations of the Dielectronic Recombination (DR) process. This is the dominant recombination mechanism for the determination of the ionization-recombination balance for non-hydrogenic ions in the important temperature region of laboratory and astrophysical plasmas. Using a state-of-the-art detailed investigation of this complex electron-ion recombination process, which involves a multitude of competing autoionization and radiative-decay channels, she has made significant contributions to the understanding of the plasma radiation generated in Z-pinch devices and the x-ray laser gain for neon-like ions. She is internationally recognized for her important contributions to the precise description of this intricate atomic process, together with applications to the improved understanding of atomic interactions in plasmas. She has also used this expertise in analyzing spectra from astrophysical phenomena such as shock waves, stellar winds, and accretions of iron rich knots in Super Novae Remnants. Dr. Dasgupta has made important contributions to the description of the interaction of intense, ultra-short-pulse laser radiation with clusters (a unique combination of gas and solid phase with small, multi-atom particles between 10 and 3x106) of noble gas atoms, particularly Xe. The collisional and radiative atomic data set that she has provided is instrumental in understanding the mechanism of laser interaction with these clusters. As a result of this modeling effort, fundamental insights have emerged regarding the conversion of the incident laser radiation into x-ray radiation, together with the production of exotic double-vacancy states of the atoms. Dr. Dasgupta's highly accurate and extremely challenging atomic structure and collision calculations of rare gases and other complex atoms are of critical importance for a wide-range of applications. Her benchmark calculations used to model unique electron beam pumped KrF and Ar-Xe gas lasers developed at NRL were instrumental for providing understanding of their inversion dynamics, gain and efficiency. Dr. Dasgupta received her bachelor's degree with honors in physics, master's degree and doctorate in atomic physics, all from the University of Maryland. She came to NRL in 1986 and has become a sought after expert in several areas of theoretical atomic and plasma physics of international importance. Her awards and professional honors include induction to the Sigma Xi Sigma honors society, and an award for excellence in physics from the Women's Society of the University of Maryland. She was elected Fellow of the American Physical Society in 2010. Dr. Dasgupta has presented numerous invited talks and colloquia and organized and chaired many invited symposia world-wide. She has served on many committees and review panels. Recently, the Director of Office of Science of the Department of Energy, Dr. Patricia Dehmer, appointed Dasgupta to serve as a member of the Fusion Energy Sciences Advisory Committee (FESAC) for the Fusion Energy Sciences (FES) program for a three-year term (2014-2017). The Committee provides advice and recommendations on scientific, technical, and programmatic issues relating to the FES program. As a committee member, Dr. Dasgupta will provide advice to the Department of Energy on the National Fusion Energy Sciences Program, specifically in her areas expertise — basic plasma science and high energy density plasma physics. Additionally, Dr. Dasgupta was appointed to serve on the FESAC Strategic Planning Panel to assess the priorities among continuing and potential new FES program investments. She contributed to a report on prioritizing program elements defined by FES, including views on new facilities, new research initiatives, and facility closures. She is a reviewer of DOE's awards nominations, and a reviewer of DOE and NSF/DOE Joint Partnership in High Energy Density Science and Laser Plasma Interactions proposals. Dr. Dasgupta currently chairs the Committee of Women in Plasma Physics of the American Physical Society's (APS) Division of Plasma Physics. She has served on the APS Division of atomic and molecular physics (DAMOP) program and education committees. She also served on the Atomic Physics panel of DOE's HEDP basic research needs international workshop to participate in writing a report on the status and future goals of HED physics. She serves on NASA's Solar and Heliospheric proposals review panels, reviews prestigious scientific journals, and has organized Indo-US Science and Technology Bilateral workshops. She is active in a number of professional and educational outreach efforts at NRL and in the physics community. She was invited to write a book chapter titled "Blazing the Trail; Essays by Leading Women in Science" in 2013 to encourage young women to pursue science careers. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.


News Article
Site: http://www.nrl.navy.mil/media/news-releases/

The U.S. Naval Research Laboratory (NRL), in collaboration with numerous universities and government laboratories studying the effects of dusty plasmas — charged dust particles that can occur naturally in the mesosphere — generated an artificial plasma cloud in the upper-atmosphere to validate the theory of 'dressed particle scattering' caused by this phenomenon. Named the Charged Aerosol Release Experiment (CARE II), an instrumented rocket was launched Sept. 16, at 19:06 GMT, from Andoya, Norway, utilizing a NASA Black Brant XI sounding rocket. After entering the ionosphere, 37 small rockets were fired simultaneously to inject 68 kilograms (kg) of dust comprised of aluminum oxide particulates, accompanied by 133 kg of molecules such as carbon dioxide, water vapor, and hydrogen. The launch occurred just after sunset placing the dust particles in sunlight for easy viewing by cameras in darkness on the ground and with an airborne platform. The large concentration of dust and exhaust material interacted with the ionosphere to produce a so-called 'dirty plasma' with high-speed pickup ions. Visibly seen from the ground, the released dust produces an optical cloud, and, by attaching the electrons in the ionosphere, forms charged particulates. This plasma then generates waves that scatter radar signals used for remote sensing. "The CARE launch was fully successful," says Dr. Paul A. Bernhardt, CARE principal investigator. "Ground-based radars tracked the effects on the ionosphere for twenty minutes, providing valuable data on how rocket motors affect ionospheric densities. The data will be used to validate simulations of natural disturbances in the upper atmosphere." The NRL Plasma Physics Division's (PPD) Charged Particle Physics Branch and the University of Washington made measurements with plasma probes and electric field booms on a deployable instrument payload. Ionospheric disturbances were monitored with multi-frequency beacon transmissions from the rocket payload that were detected by a network of ground receivers from the Finnish Meteorological Institute (FMI), Sodankylä Geophysical Observatory (SGO), and NRL PPD. Ground radars and optical instruments that recorded the dust release were provided by the European Incoherent Scatter Scientific Association (EISCAT); Institute of Atmospheric Physics (Germany); Institute of Space Physics, (Sweden); and others. The CARE theory effort was based in PPD and the Laboratory for Computational Physics and Fluid Dynamics (LCPFD) at NRL, as well as the Center for Space Science and Engineering Research at Virginia Tech. High frequency receivers were fielded by QinetiQ (UK) and by NRL PPD with stations in Oslo, Tromsö, and the University Center in Svalbard (UNIS). A CARE data review is scheduled for December 2015 in San Francisco. During this review, Bernhardt says, the scientific results from the experiment will be compared with artificial and natural scatter processes to better understand the physics. Also, a follow-on CARE III experiment will be planned. The Department of Defense (DoD) Space Test Program sponsored the launch and payload integration for the NRL CARE II mission. The rocket launch, and payload development was provided by the NASA Sounding Rocket Program. The CARE experiments were designed to test the theory of dusty plasma scatter developed by scientists at the University of Tromsö in Norway and NRL PPD. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.


Bruce R.W.,Bethel College at North Newton | Fliflet A.W.,Plasma Physics Division | Huey H.E.,HWave LLC | Stephenson C.,University of Notre Dame | Imam M.A.,Washington Technology
Key Engineering Materials | Year: 2010

The emerging reduction technologies for titanium from ore produce powder instead of sponge. Conventional methods for sintering and melting of titanium powder are costly, as they are energy intensive and require high vacuum, 10 -6 Torr or better, since titanium acts as a getter for oxygen at high temperature, adversely affecting mechanical properties. Other melting processes such as plasma arcs have the additional problem of electrode consumption, and direct induction heating of the titanium powder is problematic. Microwave sintering or melting in an atmospheric pressure argon gas environment is potentially cost effective and energy efficient due to the possibility of direct microwave heating of the titanium powder augmented by hybrid heating in a ceramic casket. We are investigating this approach at the Naval Research Laboratory using an S-Band microwave system. The experimental setup and the results of melting and sintering experiments will be described including a rough estimate of energy usage. © (2010) Trans Tech Publications. Source

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