Analytic models of high-temperature hohlraums
A unified set of high-temperature-hohlraum models has been developed. For a simple hohlraum, P{sub S}=[A{sub S}+(1-{alpha}{sub W})A{sub W}+A{sub H}]{sigma}T{sub R}{sup 4}+(4V{sigma}/c)(dT{sub R}{sup 4}/dt), where P{sub S} is the total power radiated by the source, A{sub S} is the source area, A{sub W} is the area of the cavity wall excluding the source and holes in the wall, A{sub H} is the area of the holes, {sigma} is the Stefan-Boltzmann constant, T{sub R} is the radiation brightness temperature, V is the hohlraum volume, and c is the speed of light. The wall albedo {alpha}{sub W}equivalent to(T{sub W}/T{sub R}){sup 4} where T{sub W} is the brightness temperature of area A{sub W}. The net power radiated by the source P{sub N}=P{sub S}-A{sub S}{sigma}T{sub R}{sup 4}, which suggests that for laser-driven hohlraums the conversion efficiency {eta}{sub CE} be defined as P{sub N}/P{sub Laser}. The characteristic time required to change T{sub R}{sup 4} in response to a change in P{sub N} is 4V/c[(1-{alpha}{sub W})A{sub W}+A{sub H}]. Using this model, T{sub R}, {alpha}{sub W}, and {eta}{sub CE} can be expressed in terms of quantities directly measurable in a hohlraum experiment. For a steady-state hohlraum that encloses a convex capsule, P{sub N}={l_brace}(1-{alpha}{sub W})A{sub W}+A{sub H}+[(1-{alpha}{sub C})A{sub C}(A{sub S}+{alpha}{sub W}A{sub W})/A{sub T}]{r_brace}{sigma}T{sub RC}{sup 4}, where {alpha}{sub C} is the capsule albedo, A{sub C} is the capsule area, A{sub T}equivalent to(A{sub S}+A{sub W}+A{sub H}), and T{sub RC} 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.
- Research Organization:
- Sandia National Laboratory
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 40277015
- Journal Information:
- Physical Review E, Journal Name: Physical Review E Journal Issue: 2 Vol. 64; ISSN 1063-651X
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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