Evaluation of a Foam Buffer Target Design for Spatially Uniform Ablation of Laser-Irradiated Plasmas

Dunne, Mike; Borghesi, M.; Iwase, A.; Jones, M.W.; Taylor, R. J.; Willi, O.; Gibson, R.; Goldman, S. R.; Mack, J. M.; Watt, R. G.

doi:10.1103/physrevlett.75.3858

Cited by 75 publications

(31 citation statements)

References 13 publications

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“…This includes work with high-Z layers on aluminum targets 9 , the use of low density foams 10 , the use of external x-rays before the laser pulse to create a plasma 11 , the use of foams preheated by x-rays 12,13,14,15,16 and use of a high-Z layer on the plastic membrane of a cryogenic deuterium-loaded-foam targets. 17 The most extensive experimental work has involved use of a low-density plastic foam layer that is heated by x-rays from a thin high-Z layer during the initial portion of the laser pulse.…”

Section: Introductionmentioning

confidence: 99%

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

et al. 2002

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We present experimental results and simulations that study the effects of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of laser accelerated plastic targets. These experiments employ a laser pulse with a low-intensity foot that rises into a high-intensity main pulse. This pulse shape simulates the generic Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. We present experimental results and simulations that study the effects of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of laser accelerated plastic targets. These experiments employ a laser pulse with a low-intensity foot that rises into a high-intensity main pulse. This pulse shape simulates the generic shape needed for high-gain fusion implosions. Imprint of laser nonuniformity during start up of the low intensity foot is a well-known seed for hydrodynamic instability. We observe large reductions in hydrodynamic instability seeded by laser imprint when certain minimum thickness gold or palladium layers are applied to the laser-illuminated surface of the targets. The experiment indicates that the reduction in imprint is at least as large as that obtained by a 6 times improvement in the laser uniformity. We present simulations supported by experiments showing that during the low intensity foot the laser light can be nearly completely absorbed by the high-Z layer. X-rays originating from the high-Z layer heat the underlying lower-Z plastic target material and cause large buffering plasma to form between the layer and the accelerated target. This long-scale plasma apparently isolates the target from laser nonuniformity and accounts for the observed large reduction in laser imprint. With onset of the higher intensity main pulse, the high-Z layer expands and the laser light is transmitted. This technique will be useful in reducing laser imprint in pellet implosions and thereby allow the design of more robust targets for high-gain laser fusion. Prescribed by ANSI Std Z39-18 2 shape needed for high-gain fusion implosions. Imprint of laser nonuniformity during start up of the low intensity foot is a well-known seed for hydrodynamic instability. We observe large reductions in hydrodynamic instability seeded by laser...

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Section: Introductionmentioning

confidence: 99%

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

et al. 2002

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“…LASNEX predicts that the critical density 8. 9 x 1021 e-/cm3 exceeds the fully ionized uniform foam density. So in uniform plasma none of the shock structures of Fig.…”

Section: Calculational Results and Discussionmentioning

confidence: 99%

Foam-buffered laser-matter interactions

Mason¹,

Kopp²,

Vu³

et al. 1997

The 13th International Conference on Laser Interactions and Related Plasma Phenomena

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Los Alamos National Laboratory, an affirmative actionkqual opportunity employer, is operated by the University of California for the U.S. Department of Energy under contract W-7405ENG-36. By acceptance of this article, the publisher recognizes that the U.S. Wemrnent retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. The Los Alamos National laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. Form 836 (10196)Portions of this document m y be illegible in electronic image products. b a g s are pnrduced from the best mailable original docum- DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or mpoirsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or senice by trade name, trademark, manufacturer, or otherwise does not necessan'ly constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. FOAM-BUFFERED LASER-MATTER INTERACTIONS

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“…The interaction of laser light with the low-density porous or foam-like material is considered as very important and suitable in advanced inertial confinement fusion (ICF) target design. In the direct drive scheme, it is possible to significantly alter the spatial density distribution of the plasma corona that forms at the illuminated surface of a spherical thermonuclear target by depositing, on the surface, a layer of foam material with a suitably chosen thickness and initial density made from elements with low atomic numbers [1][2][3]. This will lead to efficient smoothening, i.e.…”

Section: Introductionmentioning

confidence: 99%

Laser interaction with low-density carbon foam

et al. 2010

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Experiments were performed with a 15 J/500 ps Nd:glass laser (λ = 1064 nm) focussed to an intensity >10 14 W/cm 2 . X-ray emissions from carbon foam and 5% Pt-doped carbon foam of density 150-300 mg/cc were compared with that of the solid carbon targets. The thickness of the carbon foam was 15 μm on a graphite substrate. X-ray emission was measured using semiconductor X-ray diodes covered with various filters having transmissions in different X-ray spectral ranges. It covered X-ray spectrum of 0.8-8.5 keV range. The X-ray emission in the soft X-ray region was observed to increase to about 1.8 times and 2.3 times in carbon foam and Pt-doped foam, respectively with respect to solid carbon. In hard X-rays, there was no measurable difference amongst the carbon foam, Pt-doped carbon foam and solid carbon. Scanning electron microscope (SEM) analysis demonstrates that foam targets smoothens the crater formed by the laser irradiation.

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Evaluation of a Foam Buffer Target Design for Spatially Uniform Ablation of Laser-Irradiated Plasmas

Cited by 75 publications

References 13 publications

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

Foam-buffered laser-matter interactions

Laser interaction with low-density carbon foam

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