Refractive index gradients in nuclear-reactor-pumped lasers: Gasdynamic effects
In nuclear-reactor-pumped lasers, the fission-fragment energy deposition is spatially nonuniform, with less energy deposited near the laser axis than is deposited near the side walls from which the fission fragments originate. This nonuniformity causes gas to move toward the laser axis and established density and refractive index gradients perpendicular to the laser axis. In order to understand this phenomenon and describe it quantitatively, a numerical model of the gasdynamics of nuclear-reactor-pumped lasers has been developed. The numerical model simulates the two-dimensional motion of a perfect gas experiencing fission-fragment energy deposition in a rectangular or cylindrical enclosure. In addition to calculating mass density, temperature, pressure, velocity, and power density fields, ray-tracing calculations are performed to determine the beam steering caused by the varying gas density. The simulation of a representative one-dimensional rectangular case is found to be in excellent agreement with the existing analytical theory. In this case, the ray-tracing calculations indicate length limitations which result from internal focusing. Examination of cylindrical cases reveals that under certain circumstances gas motion reduces the on-axis power deposition to zero, a phenomenon termed axis-shielding. This phenomenon never occurs in rectangular cases. Simulations of experiments show good agreement between calculated and experimental Hartmann probe refractive index data. 13 refs., 17 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5412068
- Report Number(s):
- SAND-87-1252C; CONF-871254-3; ON: DE88006099
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
420300* -- Engineering-- Lasers-- (-1989)
CONTINUITY EQUATIONS
DIFFERENTIAL EQUATIONS
EQUATIONS
FISSION FRAGMENTS
LASERS
NUCLEAR FRAGMENTS
OPTICAL PROPERTIES
PARTIAL DIFFERENTIAL EQUATIONS
PHYSICAL PROPERTIES
POWER DENSITY
REACTORS
REFRACTIVITY
RESEARCH AND TEST REACTORS
RESEARCH REACTORS
SIMULATION