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Hyperveolcity impacts on aluminum from 6 to 11 km/s for hydrocode benchmarking

Chhabildas, L.C.; Reinhart, William D.; Thornhill III, Tom F.; Bessette, Greg C.; Saul, W.V.; Lawrence, R.J.; Kipp, Marlin E.

A systematic computational and experimental study is presented on impact generated debris resulting from record-high impact speeds recently achieved on the Sandia three-stage light-gas gun. In these experiments, a target plate of aluminum is impacted by a titanium-alloy flyer plate at speeds ranging from 6.5 to 11 km/s, producing pressures from 1 Mb to over 2.3 Mb, and temperatures as high as 15000 K (>1 eV). The aluminum plate is totally melted at stresses above 1.6 Mb. Upon release, the thermodynamic release isentropes will interact with the vapor dome. The amount of vapor generated in the debris cloud will depend on many factors such as the thickness of the aluminum plate, super-cooling, vaporization kinetics, the distance, and therefore time, over which the impact-generated debris is allowed to expand. To characterize the debris cloud, the velocity history produced by stagnation of the aluminum expansion products against a witness plate is measured using velocity interferometry. X-ray measurements of the debris cloud are also recorded prior to stagnation against an aluminum witness plate. Both radiographs and witness-plate velocity measurements suggest that the vaporization process is both time-dependent and heterogeneous when the material is released from shocked states around 230 GPa. Experiments suggest that the threshold for vaporization kinetics in aluminum should become significant when expanded from shocked states over 230 GPa. Numerical simulations are conducted to compare the measured x-ray radiographs of the debris cloud and the time-resolved experimental interferometer record with calculational results using the 3-D hydrodynamic wavecode, CTH. Results of these experiments and calculations are discussed in this paper.

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TYPE Report YEAR 2003
DOIOSTI

Final Report on LDRD Project: High-Bandwidth Optical Data Interconnects for Satellite Applications

Sanchez, Victoria; Sullivan, Charles T.; Allerman, Andrew A.; Rienstra, Jeffrey L.; Serkland, Darwin K.; Geib, Kent M.; Blansett, Ethan; Karpen, Gary D.; Peake, Gregory M.; Hargett, Terry

This report describes the research accomplishments achieved under the LDRD Project ''High-Bandwidth Optical Data Interconnects for Satellite Applications.'' The goal of this LDRD has been to address the future needs of focal-plane-array (FPA) sensors by exploring the use of high-bandwidth fiber-optic interconnects to transmit FPA signals within a satellite. We have focused primarily on vertical-cavity surface-emitting laser (VCSEL) based transmitters, due to the previously demonstrated immunity of VCSELs to total radiation doses up to 1 Mrad. In addition, VCSELs offer high modulation bandwidth (roughly 10 GHz), low power consumption (roughly 5 mW), and high coupling efficiency (greater than -3dB) to optical fibers. In the first year of this LDRD, we concentrated on the task of transmitting analog signals from a cryogenic FPA to a remote analog-to-digital converter. In the second year, we considered the transmission of digital signals produced by the analog-to-digital converter to a remote computer on the satellite. Specifically, we considered the situation in which the FPA, analog-to-digital converter, and VCSEL-based transmitter were all cooled to cryogenic temperatures. This situation requires VCSELs that operate at cryogenic temperature, dissipate minimal heat, and meet the electrical drive requirements in terms of voltage, current, and bandwidth.

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TYPE SAND Report YEAR 2003
DOIDOIOSTIOSTI

Computer Science Research Institute 2002 Annual Report of Activities

Womble, David E.; Delap, Barbara J.; Ceballos, Deanna R.

This report summarizes the activities of the Computer Science Research Institute (CSRI) at Sandia National Laboratories during the period January 1, 2002 to December 31, 2002. During this period the CSRI hosted 172 visitors representing 95 universities, companies or laboratories. Of these 56 were summer students or faculty. The CSRI also organized and hosted five workshops with 171 participants. Of these 94 attendees were from 64 universities, companies or laboratories, and 77 were from Sandia. Finally, the CSRI sponsored 14 long-term collaborative research projects.

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TYPE Report YEAR 2003
DOIDOIOSTIOSTI

Growth and Characterization of Quantum Dots and Quantum Dots Devices

Cederberg, Jeffrey G.; Biefeld, Robert M.; Chow, Weng W.

Quantum dot nanostructures were investigated experimentally and theoretically for potential applications for optoelectronic devices. We have developed the foundation to produce state-of-the-art compound semiconductor nanostructures in a variety of materials: In(AsSb) on GaAs, GaSb on GaAs, and In(AsSb) on GaSb. These materials cover a range of energies from 1.2 to 0.7 eV. We have observed a surfactant effect in InAsSb nanostructure growth. Our theoretical efforts have developed techniques to look at the optical effects induced by many-body Coulombic interactions of carriers in active regions composed of quantum dot nanostructures. Significant deviations of the optical properties from those predicted by the ''atom-like'' quantum dot picture were discovered. Some of these deviations, in particular, those relating to the real part of the optical susceptibility, have since been observed in experiments.

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TYPE Report YEAR 2003
DOIOSTIDOIOSTI
Results 91151–91200 of 100,993
Results 91151–91200 of 100,993
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