Two Dimensional Effects in Laser Solid Simulation Studies.
Abstract
The objective of this program was to study the two-dimensional wave motions induced in a target by high-power laser radiation. For these studies the target is an axisymmetric, supersonic free-jet of gas which is laser irradiated on axis. The transparency of the target permits luminosity and schlieren streak photography of the waves that propagate into the high-pressure plenum. Measurements of the axial and lateral luminous-plasma growth and of the axial shock-wave growth in the plenum have been obtained over a range of plenum pressures and laser powers. It has been found that the axial luminous-front growth can be predicted by a deflagration model; in this model the velocity scales with absorbed power divided by gas reservoir pressure to the one-third power. The temperature of the gas behind the deflagration wave is predicted to vary with the velocity squared. Temperature measurements which utilized metal-foil spectrometers to determine the relative x-ray flux in two wavelength invervals substantiated this scaling relation. The lateral expansion was found to be very slow, not even extending to the limits of the cone illuminated by the laser. Spontaneous magnetic fields are known to surround solid target during laser heating of their surfaces. Coil probes were used to determine if such fields existed near the laser-irradiated free-jet target and to measure the strength of these fields at several radial locations. An extrapolation of the data to the surface of the plasma indicate that azimuthal fields in excess of a megagauss exist. Such fields could retard the expansion of the plasma. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1976
- Accession Number
- ADA039194
Entities
People
- H. M. Thompson
- J. W. Daiber
Organizations
- Calspan