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Topic: Hohlraum

	Hohlraum
		In radiation thermodynamics, a hohlraum [in literal german "hollow area" or "cavity" a term of art synonymous with radiation case], is a cavity whose walls are in radiative equilibrium with the radiant energy within the cavity.
		This includes mitigation of x-ray nonuniformity and imprinting by foam “buffering” (as in a dynamic hohlraum, in which the plasma sheath is moving).
		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 that X rays are radiated from a large fraction of the solid angle surrounding the capsule.
	www.globalsecurity.org /wmd/intro/hohlraum.htm (1074 words)

	Review of the Department of Energy's Inertial Confinement Fusion Program
		The two major scientific uncertainties in predicting ignition with the NIF are the laser-plasma interactions in the hohlraum and the hydrodynamic instabilities in the imploding capsule.
		Integrated modeling of the hohlraum and capsule and experiments showed that the plasma from the CH liner would stagnate on the axis and destroy the symmetry of the implosion.
		Gas-filled hohlraums have shown two problematic effects: (1) a temporally dependent shift from the calculated symmetry of irradiation, equivalent to a beam position shift, and (2) a difference between measurements and modeling predictions (most importantly in radiation drive temperature).
	www.nap.edu /html/icf/icf3.htm (2781 words)

	Science News Daily
		Various diagnostic instruments measured the X-ray spectra and radiation temperatures inside the hohlraum, and imaged the X-rays that were sufficiently energetic to exit through the hohlraum wall.
		The goal was clearly achieved with a series of different-sized hohlraums irradiated with two nanosecond laser pulses of about eight trillion watts, which produced radiation temperatures in agreement with both theoretical expectations and previous experience from other facilities.
		The series of experiments was the first hohlraum campaign on NIF and part of a larger four-campaign effort, coordinated by the Lab's Nino Landen, and involving researchers from Lawrence Livermore National Laboratory, Los Alamos National Laboratory, the United Kingdom's Atomic Weapons Establishment (AWE), and General Atomics.
	www.sciencenewsdaily.org /story-8700.html (643 words)

	Topical Area DEF-1 Title: Fusion Power_______Page 1.
		For indirect drive, the capsule is contained within a metal "hohlraum" which converts the driver energy into x-rays to drive the capsule.
		ICF hohlraums are made by electroplating the hohlraum material, generally gold, onto a mandrel which is dissolved, leaving the empty hohlraum shell.
		Placement of the capsule at the center of the hohlraum must be accurate to within 25 µm.
	www.fusion.ucla.edu /snowmass/questions/pq3/IFE_target_fab_2.html (1131 words)

	Microengineering Techniques for Fabricating Planar Foils for use in Laser Targets
		The result of the laser hitting the inside of the hohlraum is that the gold walls rapidly heat to very high temperatures (a few million degrees) so that they emit x-rays and generate a shock wave that travels down the confines of the hohlraum.
		The hohlraum walls must have a minimum thickness of 25microns in order to prevent the structure disintegrating and also to stop the x-rays penetrating outwards.
		These anticipated problems were as follows: compatibility of the polyimide with both the underlying conductive film and the subsequent electroplating process; interfacing the two polyimide layers after prior pattern transfer; controlling surface finish of electroplated film.
	www.personal.dundee.ac.uk /~rpkeatch/Fusion2000HARMs.htm (1506 words)

	Z pinch driven inertial confinement target physics (Site not responding. Last check: 2007-09-08)
		As in the static walled hohlraum, the symmetry of the X ray flux at the capsule surface can be tuned by the placement and the number of the symmetry shields within the central ICF capsule hohlraum and through varying the length and diameter of the hohlraum.
		The dynamic hohlraum concept is being investigated on the Z facility using the experimental configuration shown in Fig.
		Dimensions of the hohlraums, X ray shields and capsules used in the experiments are indicated in the drawings on the left hand side of the figure.
	epub.iaea.or.at /fusion/subscribe/39/sep/ms6654LeepeR/6654.html (6041 words)

	Physics Division \| Research Highlights \| Los Alamos National Laboratory
		Their kinetic energy is converted into thermal energy, which radiates away in the form of x-rays that are absorbed and re-radiated inside the hohlraum body.
		The wall of the hohlraum can then be populated with multiple physics packages for studies of radiation flow inside closed geometries and flow through free-standing low-density foams and for studies of aperture closure driven by radiation and shocks that impinge on the gold hohlraum wall.
		Alternatively, the dynamic hohlraum produces radiation from a wire array as it impacts upon a low-density foam located in the center of the array, subsequently thermalizing the kinetic energy in the wires and radiating the energy vertically.
	www.lanl.gov /p/rh03_watt.shtml (1942 words)

	Session 3E - Hohlraum Physics.
		Data collected with time-integrated and time-resolved x-ray imaging diagnostics of the beam-spot irradiation pattern on the inside of the hohlraum and on surrogate alignment spheres were used to assess the pointing and focusing precision of the OMEGA laser system.
		Modeling of hohlraum drive-symmetry experiments at OMEGA is being undertaken to determine the accuracy of design simulations for the National Ignition Facility.
		Thin-Wall hohlraums were employed, providing simultaneous imaging of the laser-spot motion and the capsule implosion in high-energy X-rays transmitted through the walls.
	flux.aps.org /meetings/BAPSDPP96/abs/S190.html (2311 words)

	ANS : Store : Electronic Articles
		A study is conducted on cooling and controlling the thickness of a frozen layer of deuterium and tritium (D-T) on the inner surface of a capsule mounted in a cylindrical hohlraum.
		It is shown that this requirement can be satisfied by controlling the temperature rise along the hohlraum wall from the ends to the midplane.
		However, as the thermal conductivity of the capsule wall increases to metallic material values, the required accuracy of the hohlraum wall temperature rise decreases to ±15 mK.
	www.ans.org /store/index.cgi?i=E100000-fst-36-3-346-355 (216 words)

	Technology Quest. P3 Prospec
		For indirect drive, the capsule is contained within a cylindrical or spherical metal container or “hohlraum” which converts the incident driver energy into x-rays to drive the capsule.
		For current experiments, the hohlraums are a few millimeters in diameter and length.
		ICF hohlraums are currently made by electroplating the hohlraum material, generally gold, onto a diamond-turned mandrel which is dissolved, leaving the empty hohlraum shell.
	www.fusion.ucla.edu /snowmass/questions/prospectusPQ3.html (1900 words)

	Analysis of radiation symmetrization in hohlraum targets
		Symmetrization of illumination nonuniformity by thermal radiation in spherical hohlraum targets has been studied systematically for indirectly driven inertial confinement fusion.
		The second is the effect of single emission, which depends only on the hohlraum structure (area ratio).
		The third is the effect of multiple re-emission, which is equal to the reciprocal of the average circulation number of radiation in a hohlraum target.
	stacks.iop.org /0029-5515/32/1715 (292 words)

	(IF/P-18) Indirect Drive Hohlraum Design for Laser ICF
		In an indirect drive scheme, the laser light is converted in X-rays in a hohlraum made with an high-Z material.
		Part of this radiation flux is absorbed by a microballoon, filled with DT and placed in the center of the hohlraum, leading to its implosion, ignition and burn.
		The control of hohlraum energetics is then an issue for the LMJ target design.
	www.iaea.org /programmes/ripc/physics/fec2002/html/node308.htm (143 words)

	1D: Fast Z-Pinches and Radiation Sources I
		The hohlraum is created from a solid cylindrical CH target centered within an imploding tungsten wire-array z-pinch.
		By adding an identical REH at the bottom of the hohlraum, the radiation generated in the negative z direction through a bottom REH offers the possibility of doubling the utility of the hohlraum as a source of high-temperature radiation.
		The z-pinch driven hohlraum high-yield concept [1] is in the process of being experimentally validated on the Z accelerator [2], qualifying its performance with respect to hohlraum energetics [3], radiation symmetry, pulse shaping, capsule preheat, and z-pinch physics scaling.
	www.ee.ualberta.ca /icops2002/programtest/1D.htm (2400 words)

	First Experiments On National Ignition Facility Validate Computer Simulations On Road To Ignition
		A tiny gold-plated cylinder called a hohlraum holds the deuterium-tritium fuel capsule in the National Ignition Facility target chamber, where the energy from 192 high-powered lasers is converted to thermal X-rays.
		The X-rays heat and ablate the plastic surface of the ignition capsule, causing a rocket-like pressure on the capsule and forcing it to implode and ignite.
		The series of experiments was the first hohlraum campaign on NIF and part of a larger four-campaign effort, coordinated by LLNL’s Nino Landen, and involving researchers from LLNL, Los Alamos National Laboratory, the United Kingdom’s Atomic Weapons Establishment (AWE), and General Atomics.
	www.sciencedaily.com /releases/2005/12/051203122443.htm (977 words)

	HIF Target Work
		Since the beam power and intensity of present accelerators for heavy-ion fusion are orders of magnitude below values required to ignite a capsule, target-design research in the US is aimed at improving the target performance in numerical simulations.
		In an indirect-drive target, ion beams are absorbed by a cylindrical metal shell, called a Hohlraum, surrounding the fuel capsule, and the energy is reradiated as X rays.
		During the last several years, target physicists have developed a new family of designs in which the ion beams are absorbed in the Hohlraum walls, so that X rays are radiated from a large fraction of the solid angle surrounding the capsule.
	hif.lbl.gov /theory/target_summary.html (602 words)

	It's all in motion when simulating fluids
		When NIF's laser beams simultaneously deposit their energy on the hohlraum's inner surface, much of it is converted to thermal x rays.
		When the x rays ablate the surface of the capsule, they create a rocketlike effect that causes the capsule to implode, producing high temperatures and pressures in the fusion fuel.
		The code is flexible enough to model intrinsic asymmetries that result from the ideal laser illumination pattern and those that result from effects of irregularities in laser pointing and power balance.
	www.eurekalert.org /features/doe/2004-12/dlnl-iai122204.php (2306 words)

	newscast: oemagazine.com: Powered by oe magazine. The Monthly Publication of SPIE—The International Society for ... (Site not responding. Last check: 2007-09-08)
		Laurance J. Suter [pronounced Sutter] is an expert in the design and utilization of hohlraums, the tiny gold containers that hold a laser target as intense X-rays heat it during inertial confinement fusion experiments.
		As the group leader of the Hohlraum Dynamics Group in A/X Division at the Lab, Dr. Suter's work has most recently focused on the understanding and control of laser hohlraum physics at the Lab's National Ignition Facility (NIF).
		His work on hohlraum X-ray physics has also led to the development of novel high efficiency X-ray sources for a variety of other applications.
	oemagazine.com /newscast/071003_newscast01.html (338 words)

	Smooth Fusion Lasers
		The NIF design would improve the homogeneity of heating by surrounding the capsule with a gas-filled "hohlraum," a small gold cylindrical shell that is directly heated by the lasers and bathes the capsule in the x-ray glow from its extreme temperature.
		As the lasers blast their target, the capsule, gas, and inner hohlraum walls immediately turn to plasma, a hot soup of electrons and ions.
		The new results resolve one of the lingering fundamental questions regarding the gas-filled hohlraum design for the NIF, according to Robert McCrory, director of the University of Rochester's Laboratory for Laser Energetics in Rochester, NY.
	focus.aps.org /story/v1/st6 (539 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations (Site not responding. Last check: 2007-09-08)
		A dynamic hohlraum is formed when an imploding annular cylindrical Z-pinch driven plasma collides with an internal low density convertor.
		Due to the closed geometry of the dynamic hohlraum, the most convenient way to diagnose the radiation symmetry is to image the x rays from the core of an imploded capsule.
		Using numerical simulations we have redesigned the dynamic hohlraum to obtain higher capsule core temperatures.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20455100 (482 words)

	WorldNetDaily: Chinese spy gets slapped
		It involved a device called a hohlraum, which the U.S. government intends to use as the basis for creating computer models to simulate hydrogen bomb detonations.
		A hohlraum is a windowed capsule made of gold about the size of a large Tylenol tablet.
		Twogood, an authorized classifier, determined on further study that it was indeed Secret, and was ready to testify to that effect, even though he almost certainly would have been attacked by Lee's defense attorneys, who would have used against him both the Navy memo and his own uncertain first impression.
	www.worldnetdaily.com /news/printer-friendly.asp?ARTICLE_ID=17480 (5325 words)

	Experiments and 2D Hydrocode Calculations to Characterise a Single-ended Omega Hohlraum (Site not responding. Last check: 2007-09-08)
		Such hohlraums are used in many kinds of experiments, including the supersonic-jet experiment (see companion poster paper, Foster et al.).
		This hohlraum design is particularly susceptible to the formation of a stagnation region along the hohlraum axis, which generates an additional hydrodynamic drive at late time.
		A shock is launched in the aluminium which propagates into a solid CH cylinder mounted on the non-driven side of the aluminium.
	flux.aps.org /meetings/YR00/DPP00/abs/S2360057.html (204 words)

	(IFP/18) Simulations of ICF Hohlraum and Radiation Hydrodynamics in a Plastic Foil
		In this paper we study the effects of various parameters on the estimation of radiation temperature inside indirect drive ICF hohlraum and compare results with the published work.
		The radiation temperature inside a cylindrical hohlraum is seen to be strongly dependent on the number of frequency groups used.
		A three term equation of state is used for these studies and data for CHBr is generated by scaling density, atomic number and weight of the high-density polysterene (CH)n to that of CHBr.
	www-pub.iaea.org /MTCD/publications/PDF/csp_008c/html/node279.htm (208 words)

	Articles - Inertial confinement fusion (Site not responding. Last check: 2007-09-08)
		Modern cryogenic targets tend to freeze a thin layer of the D-T mix just on the inside of a plastic sphere while irradiating it with a low power IR laser to smooth it's inner surface and monitoring it with a microscope equipped camera, thereby allowing the layer to be closely monitored ensuring its "smoothness".
		Often indirect drive hohlraum targets are used to simulate thermonuclear weapons tests due to the fact that the fusion fuel in them is also imploded mainly by X-ray radiation.
		On the downside, it is very difficult to achieve the very high energies required to implode a target efficiently and most ion-beam systems require the use of a hohlraum surrounding the target, reducing the overall efficiency of the coupling of the ion beam's energy to that of the imploding target further.
	www.mupin.com /articles/Inertial_confinement_fusion (2112 words)

	F150online Forums - 2 quarts of trany fluid in under 3k miles?
		The idea about a vacuum modulator is a good one but it applied to 94 and older rangers/explorers/aerostars and older F-series with a C-6 but does not apply to a 2002 F-150 with 4r70w.
		hohlraum, when you take the truck back to check for the leak/dye test, have them check the transfer case fluid level, most likely it will be way overfull.
		Yes hohlraum, check your trans fluid level once engine/trans are hot.
	www.f150online.com /forums/showthread.php?t=178488 (1158 words)

	Nat' Academies Press, Review of the Department of Energy's Inertial Confinement Fusion Program: The National Ignition ...
		The long scale-length plasmas of the NIF hohlraum.
		As shown in Table 1, the new experiments reduced the values achieved for the HLP 1, 2, 4, 5, and 6 milestones (in most respects, below the NTC requirements) but enhanced the understanding of the underlying physics and made the results more relevant to the NIF design.
		With respect to (2), propagation of the laser light through relatively long, subcritical-density plasmas in the hohlraum.
	www.nap.edu /openbook.php?record_id=5730&page=17 (942 words)

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