ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Reduction of stimulated scattering losses from hohlraum plasmas with laser beam smoothing (2001)

Glenzer, S. H. ; Berger, R. L. ; Divol, L. M. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 8 (2001), S. 1692-1696

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: Laser beam smoothing by spectral dispersion and by polarization smoothing has been observed to significantly reduce the scattering losses by stimulated Brillouin and stimulated Raman scattering from inertial confinement fusion hohlraums. For these measurements, the laser beam smoothing and the high-Z hohlraum wall plasma parameters approach the conditions of future inertial confinement fusion experiments. The simultaneous application of the smoothing techniques has reduced the scattering losses by almost one order of magnitude down to the 1% level. The experimental scaling of the stimulated Brillouin reflectivity compares well to modeling assuming nonlinear damping on the ion acoustic waves in three-dimensional nonlinear wave simulations and calculated hohlraum plasma conditions from radiation-hydrodynamic modeling. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1363613

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

2

Electronic Resource

Filamentation and forward Brillouin scatter of entire smoothed and aberrated laser beams (2000)

Still, C. H. ; Berger, R. L. ; Langdon, A. B. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 7 (2000), S. 2023-2032

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: Laser–plasma interactions are sensitive to both the fine-scale speckle and the larger scale envelope intensity of the beam. For some time, simulations have been done on volumes taken from part of the laser beam cross-section, and the results from multiple simulations extrapolated to predict the behavior of the entire beam. However, such extrapolation could very well miss effects of the larger scale structure on the fine-scale. The only definitive method is to simulate the entire beam. These very large calculations have not been feasible until recently, but they are now possible on massively parallel computers. Whole beam simulations show the dramatic difference in the propagation and break up of smoothed and aberrated beams.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.874055

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

3

Electronic Resource

Hohlraum energetics with smoothed laser beams (2000)

Glenzer, S. H. ; Suter, L. J. ; Berger, R. L. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 7 (2000), S. 2585-2593

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: Measurements of radiation temperatures from empty and gas-filled hohlraums heated at the Nova Laser Facility [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)] show efficient coupling of the laser power to the target when applying laser beam smoothing techniques. Scattering losses are reduced to the 3% level while the radiation temperatures increased by ∼15 eV for smoothed laser beams. The experimental findings and supporting calculations indicate that filamentation and gain for stimulated Raman and Brillouin scattering is suppressed in the hohlraum plasma for smoothed laser beams. The scaling of the radiation temperature is well described by integrated radiation hydrodynamic LASNEX modeling [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Controlled Fusion 2, 85 (1975)] following the Marshak scaling. Peak radiation temperatures are in excess of 230 eV in gas-filled hohlraums in agreement with the detailed LASNEX modeling. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.874100

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

4

Electronic Resource

Diffusive, supersonic x-ray transport in radiatively heated foam cylinders (2000)

Back, C. A. ; Bauer, J. D. ; Hammer, J. H. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 7 (2000), S. 2126-2134

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: Diffusive supersonic radiation transport, where the ratio of the diffusive radiation front velocity to the material sound speed 〉2 has been studied in experiments on low density (40 mg/cc to 50 mg/cc) foams. Laser-heated Au hohlraums provided a radiation drive that heated SiO2 and Ta2O5 aerogel foams of varying lengths. Face-on emission measurements at 550 eV provided clean signatures of the radiation breakout. The high quality data provides new detailed information on the importance of both the fill and wall material opacities and heat capacities in determining the radiation front speed and curvature. The Marshak radiation wave transport is studied in a geometry that allows direct comparisons with analytic models and two-dimensional code simulations. Experiments show important effects that will affect even nondiffusive and transonic radiation transport experiments studied by others in the field. This work is of basic science interest with applications to inertial confinement fusion and astrophysics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.874057

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

5

Electronic Resource

Turbulent hydrodynamics experiments using a new plasma piston : The 41st annual meeting of the division of plasma physics of the american physical society (2000)

Edwards, J. ; Glendinning, S. G. ; Suter, L. J. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 7 (2000), S. 2099-2107

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: A new method for performing compressible hydrodynamic instability experiments using high-power lasers is presented. A plasma piston is created by supersonically heating a low-density carbon based foam with x-rays from a gold hohlraum heated to ∼200 eV by a ∼1 ns Nova laser pulse [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)]. The piston causes an almost shockless acceleration of a thin, higher-density payload consisting of a layer of gold, initially 1/2 μm thick, supported on 10 μm of solid plastic, at ∼45 μm/ns2. The payload is also heated by hohlraum x-rays to in excess of 150 eV so that the Au layer expands to ∼20 μm prior to the onset of instability growth. The Atwood number between foam and Au is ∼0.7. Rayleigh–Taylor instability, seeded by the random fibrous structure of the foam, causes a turbulent mixing region with a Reynolds number 〉105 to develop between piston and Au. The macroscopic width of the mixing region was inferred from the change in Au layer width, which was recorded via time resolved x-radiography. The mix width thus inferred is demonstrated to depend on the magnitude of the initial foam seed. For a small initial seed, the bubble front in the turbulent mixing region is estimated indirectly to grow as ∼0.036±0.19 [∫(square root of)(Ag)dt]2 which would imply for a constant acceleration 0.036±0.019 Agt2. More direct measurement techniques must be developed in larger scale experiments to remove potential complicating factors and reduce the error bar to a level that would permit the measurements to discriminate between various theories and models of turbulent mixing. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.874177

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

6

Electronic Resource

Thinshell symmetry surrogates for the National Ignition Facility: A rocket equation analysis (2001)

Amendt, Peter ; Shestakov, A. I. ; Landen, O. L. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 8 (2001), S. 2908-2917

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: Several techniques for inferring the degree of flux symmetry in indirectly driven cylindrical hohlraums have been developed over the past several years for eventual application to the National Ignition Facility (NIF) [Paisner et al., Laser Focus World 30, 75 (1994)]. These methods use various ignition capsule surrogates, including non-cryogenic imploded capsules [Hauer et al., Phys. Plasmas 2, 2488 (1995)], backlit aerogel foamballs [Amendt et al., Rev. Sci. Instrum. 66, 785 (1995)], reemission balls [Delamater, Magelssen, and Hauer, Phys. Rev. E 53, 5240 (1996)], and backlit thinshells [Pollaine et al., Phys. Plasmas 8, 2357 (2001)]. Recent attention has focussed on the backlit thinshells as a promising means for detecting higher-order Legendre flux asymmetries, e.g., P6 and P8, which are predicted to be important sources of target performance degradation on the NIF for levels greater than 1% [Haan et al., Phys. Plasmas 2, 2490 (1995)]. A key property of backlit thinshells is the strong amplification of modal flux asymmetry imprinting with shell convergence. A simple single-parameter analytic description based on a rocket model is presented which explores the degree of linearity of the shell response to an imposed flux asymmetry. Convergence and mass ablation effects introduce a modest level of nonlinearity in the shell response. The effect of target fabrication irregularities on shell distortion is assessed with the rocket model and particular sensitivity to shell thickness variations is shown. The model can be used to relate an observed or simulated backlit implosion trajectory to an ablation pressure asymmetry history. Ascertaining this history is an important element for readily establishing the degree of surrogacy of a symmetry target for a NIF ignition capsule. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1369412

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

7

Electronic Resource

Indirect-drive noncryogenic double-shell ignition targets for the National Ignition Facility: Design and analysis : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)

Amendt, Peter ; Colvin, J. D. ; Tipton, R. E. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 9 (2002), S. 2221-2233

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: Analysis and design of indirect-drive National Ignition Facility double-shell targets with hohlraum temperatures of 200 eV and 250 eV are presented. The analysis of these targets includes the assessment of two-dimensional radiation asymmetry and nonlinear mix. Two-dimensional integrated hohlraum simulations indicate that the x-ray illumination can be adjusted to provide adequate symmetry control in hohlraums specially designed to have high laser-coupling efficiency [Suter et al., Phys. Plasmas 7, 2092 (2000)]. These simulations also reveal the need to diagnose and control localized 10–15 keV x-ray emission from the high-Z hohlraum wall because of strong absorption by the high-Z inner shell. Preliminary estimates of the degree of laser backscatter from an assortment of laser–plasma interactions suggest comparatively benign hohlraum conditions. The application of a variety of nonlinear mix models and phenomenological tools, including buoyancy-drag models, multimode simulations and fall-line optimization, indicates a possibility of achieving ignition, i.e., fusion yields greater than 1 MJ. Planned experiments on the Omega laser will test current understanding of high-energy radiation flux asymmetry and mix-induced yield degradation in double-shell targets. © 2002 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1459451

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

8

Electronic Resource

National Ignition Facility scale hohlraum asymmetry studies by thin shell radiography : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)

Pollaine, S. M. ; Bradley, D. K. ; Landen, O. L. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 8 (2001), S. 2357-2364

add to mindlist on the mindlist

Details

ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: A necessary condition for igniting indirectly driven inertial confinement fusion (ICF) capsules on the National Ignition Facility (NIF) is controlling drive asymmetry to the 1% level [S. W. Haan, S. M. Pollaine, J. D. Lindl et al., Phys. Plasmas 2, 2480 (1995)]. Even flux-asymmetry modes (e.g., Legendre modes P2, P4, P6, and P8) must be reduced by hohlraum design and laser beam pointing. Odd flux-asymmetry modes (e.g., Legendre modes P1, P3, P5, etc.) are theoretically removed by reflection symmetry across the hohlraum midplane [S. M. Pollaine and D. Eimerl, Nucl. Fusion 38, 1523 (1998)], but will be produced by power imbalance, laser beam pointing errors, and target fabrication errors. An experimental campaign is now being conducted on the University of Rochester's Omega laser to measure higher order (P4 and higher) flux asymmetry modes inside hohlraums that approximate the conditions of a NIF hohlraum during the 90 eV early drive phase [S. W. Haan, S. M. Pollaine, J. D. Lindl et al., Phys. Plasmas 2, 2480 (1995)]. These experiments use a new point-projection backlighting technique [O. L. Landen, D. R. Farley, S. G. Glendinning et al., Rev. Sci. Instrum. 72, 627 (2001)] to cast high quality 4.7 keV radiographs of thin 2 mm diameter Ge-doped CH shells designed to enhance sensitivity to drive asymmetries. Distortions in the position of the limb of the shells resulting primarily from drive asymmetries are measured to an accuracy of 2 μm. The linearity and sensitivity of thin imploding shells to flux asymmetry makes it possible to achieve this degree of accuracy, which is sufficient for NIF ignition symmetry tuning. The promising results to date permit the comparison of measured and predicted distortions and, by inference, drive asymmetries for the first eight asymmetry modes. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1364514

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

9

Electronic Resource

Debris characterization diagnostic for the NIF : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)

Miller, M. C. ; Celeste, J. R. ; Stoyer, M. A. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 72 (2001), S. 537-539

add to mindlist on the mindlist

Details

ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: Generation of debris from targets and by x-ray ablation of surrounding materials will be a matter of concern for experimenters and National Ignition Facility (NIF) operations. Target chamber and final optics protection, for example debris shield damage, drive the interest for NIF operations. Experimenters are primarily concerned with diagnostic survivability, separation of mechanical versus radiation induced test object response in the case of effects tests, and radiation transport through the debris field when the net radiation output is used to benchmark computer codes. In addition, radiochemical analysis of activated capsule debris during ignition shots can provide a measure of the ablator 〈ρr〉. Conceptual design of the Debris Monitor and Rad-Chem Station, one of the NIF core diagnostics, is presented. Methods of debris collection, particle size and mass analysis, impulse measurement, and radiochemical analysis are given. A description of recent experiments involving debris collection and impulse measurement on the OMEGA and Pharos lasers is also provided. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1310587

Permalink