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confinement fusion. Hence imperfection is to be carefully prevented so surface finishing is extremely important, as during ICF laser shots, due to intense pressure and temperature, results are highly susceptible to hohlraum texture roughness. The fuel capsule must be precisely spherical, with texture roughness less than one nanometer, for fusion ignition to start. Otherwise, instability will cause fusion to fizzle. The fuel capsule contains a small fill hole with less than 5 microns diameter to inject the capsule with D-T gas.
238:, a process known as indirect drive. The advantage to this approach, compared to direct drive, is that high mode structures from the laser spot are smoothed out when the energy is re-radiated from the hohlraum walls. The disadvantage to this approach is that low mode asymmetries are harder to control. It is important to be able to control both high mode and low mode asymmetries to achieve a uniform
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light elements such as plastic, beryllium, or high density carbon, i.e. diamond. The outer portion of the fuel capsule explodes outward when ablated by the x-rays produced by the hohlraum wall upon irradiation by lasers. Due to Newton's third law, the inner portion of the fuel capsule implodes, causing the D-T fuel to be supercompressed, activating a fusion reaction.
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hohlraum. The hohlraum body is manufactured using a high-Z (high atomic number) element, usually gold or uranium. Inside the hohlraum is a fuel capsule containing deuterium and tritium (D-T) fuel. A frozen layer of D-T ice adheres inside the fuel capsule. The fuel capsule wall is synthesized using
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during compression. Earlier designs had radiators at the ends of the hohlraum, but it proved difficult to maintain adequate X-ray symmetry with this geometry. By the end of the 1990s, target physicists developed a new family of designs in which the ion beams are absorbed in the hohlraum walls, so
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material. The radiation escaping through a small perforation in the wall of such a container will be a good approximation of black-body radiation at the temperature of the interior of the container. Indeed, a hohlraum can even be constructed from cardboard, as shown by
Purcell's Black Body Box, a
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The hohlraum walls must have surface roughness less than 1 micron, and hence accurate machining is required during fabrication. Any imperfection of the hohlraum wall during fabrication will cause uneven and non-symmetrical compression of the fuel capsule inside the hohlraum during inertial
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Hohlraums are used in High Energy
Density Physics (HEDP) and Inertial Confinement Fusion (ICF) experiments to convert laser energy to thermal x-rays for imploding capsules, heating targets, and generating thermal radiation waves. They may also be used in Nuclear Weapon designs.
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surrounding the capsule. With a judicious choice of absorbing materials, this arrangement, referred to as a "distributed-radiator" target, gives better X-ray symmetry and target gain in simulations than earlier designs.
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occurs when an object achieves thermodynamic equilibrium with an enclosing hohlraum. As a consequence of
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Algorithms and
Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery IX
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word for a "hollow space", "empty room", or "cavity") is a cavity whose walls are in
409:"High-energy density hohlraum design using forward and inverse deep neural networks"
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McClarren, Ryan G.; Tregillis, Ian L.; Urbatsch, Todd J.; Dodd, Evan S. (2021).
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279:. The casing's purpose is to contain and focus the energy of the primary (
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387:"The MWIR and LWIR Spectral Signatures of Water and Associated Materials"
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The X-ray intensity around the capsule must be very symmetrical to avoid
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451:– High resolution picture at Lawrence Livermore National Laboratory.
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Dictionary of
Technical Terms for Aerospace Use. NASA SP-7
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Mockup of a gold-plated hohlraum designed for use in the
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that X-rays are radiated from a large fraction of the
345:. Vol. 7. NASA, Washington, D.C. p. 134.
374:. Harvard Natural Sciences Lecture Demonstrations.
385:Mitchell, Herbert J.; Salvaggio, Carl (2003).
392:. In Shen, Sylvia S.; Lewis, Paul E. (eds.).
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48:introducing citations to additional sources
283:) stage in order to implode the secondary (
271:is also used to describe the casing of a
38:Relevant discussion may be found on the
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396:. Vol. 5093. Proceedings of SPIE.
158:within the cavity. First proposed by
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162:in 1860 and used in the study of
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214:The indirect drive approach to
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222:fuel capsule is held inside a
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313:. Vol. 29. p. 87.
230:The radiation source (e.g.,
470:Inertial confinement fusion
216:inertial confinement fusion
199:Inertial confinement fusion
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372:"Purcell's Black Body Box"
339:Allen, William H. (1965).
251:hydrodynamic instabilities
209:National Ignition Facility
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465:Electromagnetic radiation
111:Not to be confused with
175:hohlraum demonstrator.
310:Black-Holes in History
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263:Nuclear weapon design
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178:In spectroscopy, the
152:radiative equilibrium
135:[ˈhoːlˌʁaʊ̯m]
291:Notes and references
164:black-body radiation
44:improve this article
351:1965NASSP...7.....A
319:1988QJRAS..29...87H
305:Harrison, Edward R.
218:is as follows: the
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459:Categories
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59:"Hohlraum"
287:) stage.
267:The term
240:implosion
154:with the
120:radiation
113:Holuhraun
40:talk page
434:Hohlraum
356:June 27,
324:June 28,
269:hohlraum
127:hohlraum
347:Bibcode
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