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Analytic models of high-temperature hohlraums

Stygar, William A.; Olson, Richard E.; Spielman, Rick; Leeper, Ramon J.

A unified set of high-temperature-hohlraum models has been developed. For a simple hohlraum, (Formula presented) where (Formula presented) is the total power radiated by the source, (Formula presented) is the source area, (Formula presented) is the area of the cavity wall excluding the source and holes in the wall, (Formula presented) is the area of the holes, σ is the Stefan-Boltzmann constant, (Formula presented) is the radiation brightness temperature, (Formula presented) is the hohlraum volume, and c is the speed of light. The wall albedo (Formula presented) where (Formula presented) is the brightness temperature of area (Formula presented) The net power radiated by the source (Formula presented) which suggests that for laser-driven hohlraums the conversion efficiency (Formula presented) be defined as (Formula presented) The characteristic time required to change (Formula presented) in response to a change in (Formula presented) is (Formula presented) Using this model, (Formula presented) (Formula presented) and (Formula presented) can be expressed in terms of quantities directly measurable in a hohlraum experiment. For a steady-state hohlraum that encloses a convex capsule, (Formula presented) where (Formula presented) is the capsule albedo, (Formula presented) is the capsule area, (Formula presented) and (Formula presented) is the brightness temperature of the radiation that drives the capsule. According to this relation, the capsule-coupling efficiency of the baseline National Ignition Facility hohlraum is 15–23 % higher than predicted by previous analytic expressions. A model of a hohlraum that encloses a z pinch is also presented. © 2001 The American Physical Society.