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Title: X-Ray Preheating of Window Materials in Direct-Drive Shock-Wave Timing Experiments

Abstract

The optical properties of x-ray preheated planar-window materials relevant for shock-wave timing experiments were studied on the OMEGA Laser System. The behavior of diamond windows exposed to x rays is consistent with a simple model based on the generation of free charge carriers. Polystyrene windows showed indications of optical transitions due to molecular states that are created by the ionizing radiation.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Laboratory for Laser Energetics, University of Rochester
Sponsoring Org.:
USDOE
OSTI Identifier:
897881
Report Number(s):
DOE/SF19460-719
Journal ID: ISSN 1070-664X; PHPAEN; 1681; 2006-88; TRN: US0703495
DOE Contract Number:
FC52-92SF19460
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Plasmas; Journal Volume: 13
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 36 MATERIALS SCIENCE; OMEGA FACILITY; DIRECT DRIVE LASER IMPLOSION; SHOCK WAVES; RESEARCH PROGRAMS; WINDOWS; DIAMONDS; OPTICAL PROPERTIES; POLYSTYRENE; RADIATION EFFECTS

Citation Formats

Theobald, W., Miller, J. E., Boehly, T.R., Vianello, E, Meyerhofer, D.D., Sangster, T.C., Eggert, J., and Celliers, P.M. X-Ray Preheating of Window Materials in Direct-Drive Shock-Wave Timing Experiments. United States: N. p., 2007. Web.
Theobald, W., Miller, J. E., Boehly, T.R., Vianello, E, Meyerhofer, D.D., Sangster, T.C., Eggert, J., & Celliers, P.M. X-Ray Preheating of Window Materials in Direct-Drive Shock-Wave Timing Experiments. United States.
Theobald, W., Miller, J. E., Boehly, T.R., Vianello, E, Meyerhofer, D.D., Sangster, T.C., Eggert, J., and Celliers, P.M. Wed . "X-Ray Preheating of Window Materials in Direct-Drive Shock-Wave Timing Experiments". United States. doi:.
@article{osti_897881,
title = {X-Ray Preheating of Window Materials in Direct-Drive Shock-Wave Timing Experiments},
author = {Theobald, W. and Miller, J. E. and Boehly, T.R. and Vianello, E, Meyerhofer, D.D. and Sangster, T.C. and Eggert, J. and Celliers, P.M.},
abstractNote = {The optical properties of x-ray preheated planar-window materials relevant for shock-wave timing experiments were studied on the OMEGA Laser System. The behavior of diamond windows exposed to x rays is consistent with a simple model based on the generation of free charge carriers. Polystyrene windows showed indications of optical transitions due to molecular states that are created by the ionizing radiation.},
doi = {},
journal = {Phys. Plasmas},
number = ,
volume = 13,
place = {United States},
year = {Wed Jan 24 00:00:00 EST 2007},
month = {Wed Jan 24 00:00:00 EST 2007}
}
  • The optical properties of x-ray preheated planar-window materials relevant for shock-wave timing experiments were studied on the OMEGA Laser System. The x-ray radiation was generated by 100 ps, 1x10{sup 15} W/cm{sup 2} laser pulses incident on planar plastic targets, instantaneously affecting samples located {approx}0.7 mm away. An abrupt onset of strong absorption of an optical probe beam ({lambda}=532 nm) and a temporally varying refractive index were measured in polystyrene and diamond windows. The behavior of diamond windows exposed to x rays is consistent with a simple model based on the generation of free charge carriers. Polystyrene windows showed indications ofmore » optical transitions due to molecular states that are created by the ionizing radiation.« less
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  • An innovative technique has been developed and used to measure the shock propagation speed along two orthogonal axes in an inertial confinement fusion indirect drive implosion target. This development builds on an existing target and diagnostic platform for measuring the shock propagation along a single axis. A 0.4 mm square aluminum mirror is installed in the ablator capsule which adds a second orthogonal view of the x-ray-driven shock speeds. The new technique adds capability for symmetry control along two directions of the shocks launched in the ablator by the laser-generated hohlraum x-ray flux. Laser power adjustments in four different azimuthal conesmore » based on the results of this measurement can reduce time-dependent symmetry swings during the implosion. Analysis of a large data set provides experimental sensitivities of the shock parameters to the overall laser delivery and in some cases shows the effects of laser asymmetries on the pole and equator shock measurements.« less
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  • Here, indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from a laser-driven hohlraum. Previous experiments have been unable to determine whether a deficit in measured ablator implosion velocity relative to simulations is due to inadequate models of the hohlraum or ablator physics. ViewFactor experiments allow for the first time a direct measure of the x-ray drive from the capsule point of view. The experiments show a 15%–25% deficit relative to simulations and thus explain nearly all of the disagreement with the velocity data. In addition, the datamore » from this open geometry provide much greater constraints on a predictive model of laser-driven hohlraum performance than the nominal ignition target.« less