Charged-Particle Probing of X-Ray-Driven Inertial-Fusion Implosions

International audienc

ASAP progress and expenditure report for the month of February 1--29, 1996

This is the ASAP progress and expenditure report for the month of February, 1996. The individual projects` report includes the sponsoring organization, the project identification, the principal investigator, long term objectives, short term objectives, accomplishments this reporting period, identification of issues or concerns, project budget estimate for the fiscal year, and monthly actual and year to date expenditures. The research project concerns a joint US/UK program to develop a high-priority radar system based on real aperture and synthetic aperature radar. Topics being researched include airborne RAR/SAR; radar data processor; ground-based SAR signal processing workstation; static airborne radar; radar field experiments; data analysis and detection theory; program management; modeling and analysis; UCSB wave tank; stratified wave tank; and experiments in a thermo-stratified tank at the Institute of Applied Physics, Russia

Survey of historical water column profiles for the COPE 95 experiment

A survey of historical water column profiles from the mouth of the Columbia River has been conducted. For this report, the time of year was restricted to September and latitude and longitude were restricted to the range of 45 degrees 50 minutes to 46 degrees 10 minutes latitude and 124 degrees 0 minutes to 124 degrees 30 minutes longitude. 6 profiles from 3 different years have been analyzed. For these cases, plots of the temperature, salinity, density, and Brunt- Vaisala frequency have been constructed. From the Brunt-Vaisala frequency, dispersion relations were calculated. For each case, plots of the dispersion relation, phase and group velocities and the eigenfunction of the internal wave vertical velocity are shown for the first two internal wave modes

Performance of indirectly driven capsule implosions on the National Ignition Facility using adiabat-shaping

A series of indirectly driven capsule implosions has been performed on the National Ignition Facility to assess the relative contributions of ablation-front instability growth vs. fuel compression on implosion performance. Laser pulse shapes for both low and high-foot pulses were modified to vary ablation-front growth and fuel adiabat, separately and controllably. Three principal conclusions are drawn from this study: (1) It is shown that reducing ablation-front instability growth in low-foot implosions results in a substantial (3-10X) increase in neutron yield with no loss of fuel compression. (2) It is shown that reducing the fuel adiabat in high-foot implosions results in a significant (36%) increase in fuel compression together with a small (10%) increase in neutron yield. (3) Increased electron preheat at higher laser power in high-foot implosions, however, appears to offset the gain in compression achieved by adiabat-shaping at lower power. These results taken collectively bridge the space between the higher compression low-foot results and the higher yield high-foot results

An optical technique for the direct measurement of the 2-D spectral density of a passive scalar in a turbulent flow

A new optical technique for quantitatively measuring the spectral density of passive scalar fluctuations in a turbulent flow has been developed. The technique exploits the photorefractive properties of BaTiO{sub 3} to separate the optical signal of the turbulent field from the coherent illumination background. It is a major improvement over existing techniques in that it is non-intrusive, has excellent frequency response and spatial resolution, and is capable of simultaneously measuring two components of the three-dimensional spectral density, {Phi}{theta}({kappa}). The technique is thus especially well suited to the directly study of anisotropic flows. We have applied this technique to study the spectrum of temperature fluctuations in a fully developed turbulent channel flow with heat addition. The flow is highly anisotropic, yet the spectrum in directions transverse to the flow is seen to exhibit an inertial--convective subrange behavior which is characteristic of isotropic flows. The spectral behavior in the flow direction, due to the direct influence of the mean strain rate, is observed to be markedly different. 17 refs., 7 figs