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Title: X-ray ablation measurements and modeling for ICF applications

Abstract

X-ray ablation of material from the first wall and other components of an ICF (Inertial Confinement Fusion) chamber is a major threat to the laser final optics. Material condensing on these optics after a shot may cause damage with subsequent laser shots. To ensure the successful operation of the ICF facility, removal rates must be predicted accurately. The goal for this dissertation is to develop an experimentally validated x-ray response model, with particular application to the National Ignition Facility (NIF). Accurate knowledge of the x-ray and debris emissions from ICF targets is a critical first step in the process of predicting the performance of the target chamber system. A number of 1-D numerical simulations of NIF targets have been run to characterize target output in terms of energy, angular distribution, spectrum, and pulse shape. Scaling of output characteristics with variations of both target yield and hohlraum wall thickness are also described. Experiments have been conducted at the Nova laser on the effects of relevant x-ray fluences on various materials. The response was diagnosed using post-shot examinations of the surfaces with scanning electron microscope and atomic force microscope instruments. Judgments were made about the dominant removal mechanisms for each material. Measurementsmore » of removal depths were made to provide data for the modeling. The finite difference ablation code developed here (ABLATOR) combines the thermomechanical response of materials to x-rays with models of various removal mechanisms. The former aspect refers to energy deposition in such small characteristic depths (~ micron) that thermal conduction and hydrodynamic motion are significant effects on the nanosecond time scale. The material removal models use the resulting time histories of temperature and pressure-profiles, along with ancillary local conditions, to predict rates of surface vaporization and the onset of conditions that would lead to spallation.« less

Authors:
 [1]
  1. Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
410403
Report Number(s):
UCRL-LR-125352
ON: DE97050259; TRN: 97:001207
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: DN: Thesis submitted to Univ. of California, Berkeley, CA; TH: Thesis (Ph.D); PBD: Sep 1996
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; LASER FUSION REACTORS; INDIRECT DRIVE LASER IMPLOSION; LASER TARGETS; ABLATION; OPTICAL SYSTEMS; DAMAGE; FINITE DIFFERENCE METHOD; INERTIAL CONFINEMENT; REMOVAL; LASER-PRODUCED PLASMA; LASER-RADIATION HEATING; MATHEMATICAL MODELS

Citation Formats

Anderson, Andrew Thomas. X-ray ablation measurements and modeling for ICF applications. United States: N. p., 1996. Web. doi:10.2172/410403.
Anderson, Andrew Thomas. X-ray ablation measurements and modeling for ICF applications. United States. https://doi.org/10.2172/410403
Anderson, Andrew Thomas. 1996. "X-ray ablation measurements and modeling for ICF applications". United States. https://doi.org/10.2172/410403. https://www.osti.gov/servlets/purl/410403.
@article{osti_410403,
title = {X-ray ablation measurements and modeling for ICF applications},
author = {Anderson, Andrew Thomas},
abstractNote = {X-ray ablation of material from the first wall and other components of an ICF (Inertial Confinement Fusion) chamber is a major threat to the laser final optics. Material condensing on these optics after a shot may cause damage with subsequent laser shots. To ensure the successful operation of the ICF facility, removal rates must be predicted accurately. The goal for this dissertation is to develop an experimentally validated x-ray response model, with particular application to the National Ignition Facility (NIF). Accurate knowledge of the x-ray and debris emissions from ICF targets is a critical first step in the process of predicting the performance of the target chamber system. A number of 1-D numerical simulations of NIF targets have been run to characterize target output in terms of energy, angular distribution, spectrum, and pulse shape. Scaling of output characteristics with variations of both target yield and hohlraum wall thickness are also described. Experiments have been conducted at the Nova laser on the effects of relevant x-ray fluences on various materials. The response was diagnosed using post-shot examinations of the surfaces with scanning electron microscope and atomic force microscope instruments. Judgments were made about the dominant removal mechanisms for each material. Measurements of removal depths were made to provide data for the modeling. The finite difference ablation code developed here (ABLATOR) combines the thermomechanical response of materials to x-rays with models of various removal mechanisms. The former aspect refers to energy deposition in such small characteristic depths (~ micron) that thermal conduction and hydrodynamic motion are significant effects on the nanosecond time scale. The material removal models use the resulting time histories of temperature and pressure-profiles, along with ancillary local conditions, to predict rates of surface vaporization and the onset of conditions that would lead to spallation.},
doi = {10.2172/410403},
url = {https://www.osti.gov/biblio/410403}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Sep 01 00:00:00 EDT 1996},
month = {Sun Sep 01 00:00:00 EDT 1996}
}

Thesis/Dissertation:
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