摘要:

The National Ignition Facility, as well as its French counterpart,Le Laser Megajoule, have been designed to confront one of the most difficult and compelling problem in shock physics—the creation of a hot, compressed DT plasma surrounded and confined by cold, nearly degenerate DT fuel. At the same time, these laser facilities will present the shock physics community with unique tools for the study of high energy density matter at states unreachable by any other laboratory technique. Here we describe how these lasers can contribute to investigations of high energy density matter in the areas of material properties and equations of state, extend present laboratory shock techniques such as high-speed jets to new regimes, and allow study of extreme conditions found in astrophysical phenomena. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55630

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Shock-compression experiments on liquids using a two-stage gun are described. Results forH2,He,H2O,N2,CO2,and a mixture ofH2O,NH3,andC3H8O(synthetic Uranus) are discussed and related to explosive reaction products, giant planets, laser-driven fusion, and metallic hydrogen. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55631

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A scheme is under development for predicting the equation of state of solid materials in shock-wave scenarios using a minimum of experimental data. Typically, the only experimental input is a pressure correction to match the ambient density. The equation of state is split as usual into components from the ground state of the electrons in a frozen-ion lattice, the electronic specific heat capacity and the thermal energy of the lattice. The electron ground state is calculated by a quantum-mechanical simulation of a lattice cell. The electron-thermal contribution is calculated from the band structure. The thermal energy of the lattice is found from its phonon modes. These are calculated from the forces acting on an atom displaced from its equilibrium position, e.g. by perturbing the position of atoms in the ground-state calculation. Anharmonic terms may be included. Results are presented for aluminium and silicon. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55530

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The principal Hugoniot jump relations can be cast in a differential form that relates the Gru¨neisen constant, isentropic bulk modulus, pressure, particle velocity, and shock velocity to each other through an algebraic equation. From this relation I show the general features of the Hugoniot, including a low pressure and a high pressure linear region with a connecting break in slope, limiting forms, and insensitivity to atomic shell structure. The value of the slope for high pressures is explained. The excellent agreement with data is presented. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55632

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The theory and prior experimental studies for the high pressure shock compaction of porous metals are reviewed. The Mie-Gru¨neisen and Constant Derivative Mie-Gru¨neisen equations of state are not accurate for materials of high initial porosity shocked to high pressures. The equation of state proposed by Oh and Persson for these highly porous materials reduces the Gru¨neisen parameter of high internal energy states. The Oh-Persson equation of state does not predict the larger volumes at higher shock pressures known to exist for material of low initial porosity. We have modified the Oh-Persson equation of state by using an approximate Oh-Persson equation of state that has two asymptotes: the Mie-Gru¨neisen constant at low energy states and 0.5 at high energy states. The equation of state was applied to porous tungsten and compared with experimental data from the literature and other equations of state. The proposed equation of state shows improved correlation to experimental data for tungsten with high initial porosity, and reflects the larger volumes at high shock pressures for materials with low initial density. This is achieved while maintaining the close correlation to data obtained by most equations of state at higher initial densities. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55473

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Two new theoretical methods for computing the equation of state of hot, dense matter are discussed. The ab initio phonon theory gives a first-principles calculation of lattice frequencies, which can be used to compare theory and experiment for isothermal and shock compression of solids. The ACTEX dense plasma theory has been improved to allow it to be compared directly with ultrahigh pressure shock data on low-Z materials. The comparisons with experiment are good, suggesting that these models will be useful in generating global EOS tables for hydrodynamic simulations. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55633

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The equation of state developed by Segletes is compared with prior theories. By modifying the functional relationship for the &psgr; variable and eliminating higher order terms, each of three historical theories for the Gru¨neisen function can be made to fall directly out of the model—namely, the theories of Slater, Dugdale and MacDonald, and the free-volume theory. One concludes that Segletes’ model captures the essence of all of the older theories, each of which being nominally applicable under an appropriate circumstance. The current model differs, however, from these historical models, if the higher order terms are retained. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55696

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Equation of State (EOS) data is a necessary requirement for the simulation of many dynamic processes, including shock wave propagation, high velocity impact, laser-matter interaction, laser medicine, x-ray deposition and planetary and stellar interior evolution. Realistic simulations require high accuracy and smoothness in the EOS. In addition, some processes require independent ionic, electronic and radiation physics. In order to meet these needs, we have implemented a new EOS data library that is platform independent, hierarchically structured and easily extensible for future development. We have just begun our user testing phase and are considering future improvements. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55634

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The information on thermodynamic properties of matter under conditions of extremely high pressure and temperature is collected and treated. About 10000 experimental points are stored into ASCII files and converted into SQL format. Relational SQL data base is installed on server and graphical interface is elaborated. The information can be accessed via Internet with the help of Netscape Navigator 3.0 browser. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55550

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

During nearly 50-year period of development of the dynamic methods for studying material properties Russia has accumulated a large amount of experimental data for more that 200 individual materials, compounds, condensed media and gases. It is for systematization of the accumulated experimental data and their visualization that the Database presented was developed. The base is a set of interconnected tables storing: data on shock compressibility of continuous materials and porous materials; on material compressibility by the second shock wave; expansion adiabats of shock-compressed continuous and porous materials; data on velocity of shock-compressed material scattering into air and on sound speed in shock-compressed materials. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55557

出版商:AIP    

年代:1998

数据来源: AIP