Numerical simulation of the laser-target interaction and blast-wave formation in the DNA/NRL (Defense Nuclear Agency/Naval Research Laboratory) laser experiment. Memorandum report

Technical Report · Fri May 09 00:00:00 EDT 1986

OSTI ID:5641296

Giuliani, J L

A numerical simulation of the ablation of a planar, aluminum-foil target by a neodymium laser in the presence of a 2.5 Torr nitrogen background gas is presented. The simulation includes inverse-bremsstrahlung absorption during the laser pulse, the cold isotherm in the equation of state for solid aluminum, non-equilibrium chemistry for both the target material and the background gas, radiation transport of the continuum, ion and electron energy equations, and blast-wave formation in the background gas. The simulation is followed out to > 50 nsec from the peak of the laser pulse. Although the Lagrangian code is 1-D, the divergence of the ablated target material expanding toward the laser (forward) as well as the rearward acceleration of the remaining target is accounted for by using an oblate spheroidal-coordinate system. The primary results of the simulations are as follows: (i), by about 50 nsec a cavity with T/sub e/ about 60 ev and ne about 2 x 10/sup 17//cc has formed behind the denser and cooler forward-moving blast wave; (ii), this cavity is not in chemical equilibrium but highly overionized for its temperature with predominantly Al(+9),Al(+10),Al(+11),N(+5) and N(+6); and (iii), the conditions for a deceleration-driven Rayleigh-Taylor instability are satisfied at the rear blast wave near one equal mass radius. This last feature may account for the experimentally observed floculli on the rearward side.

• Research Organization: Naval Research Lab., Washington, DC (USA)
• OSTI ID: 5641296
• Report Number(s): AD-A-167119/7/XAB; NRL-MR-5762
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ALUMINIUM
ABLATION
LASER RADIATION
INTERACTIONS
LASER WEAPONS
TARGETS
ACCELERATION
BREMSSTRAHLUNG
EQUATIONS OF STATE
HEAVY IONS
ISOTHERMS
LOW TEMPERATURE
MATHEMATICAL MODELS
NEODYMIUM LASERS
NITROGEN
NUMERICAL ANALYSIS
RAYLEIGH-TAYLOR INSTABILITY
SIMULATION
CHARGED PARTICLES
DIRECTED-ENERGY WEAPONS
ELECTROMAGNETIC RADIATION
ELEMENTS
EQUATIONS
INSTABILITY
IONS
LASERS
MATHEMATICS
METALS
NONMETALS
RADIATIONS
SOLID STATE LASERS
WEAPONS
990100* - Management