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  • American Institute of Physics (AIP)  (2)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2306-2313 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two important steps in the fabrication of microsphere laser fusion targets have been analyzed by simple mathematical modeling. Volatile-containing droplets emerging from a nozzle with imposed oscillation first undergo a spontaneous blowing process, driven by the evaporation of volatile solvent which pushes the polymeric shell outward. These hollow particles then enter a refinement zone, where a centering process takes place to eliminate eccentricity between the shell internal and external surfaces. The confined vapor partially permeates to the surroundings, allowing shrinkage of the microspheres in this zone to the desired final dimensions and sphericity. Biaxial extensional flow dominates the rheology of micropshere expansion, whereas detailed dynamics of radial flow results in improved concentricity and sphericity. The effects of viscoelasticity on the rate and stress associated with microsphere expansion have been studied using the Newtonian and Maxwell constitutive equations. Simple analytic results to describe microsphere refinement have been obtained for conditions representative of the centering process where Newtonian behavior prevails as the fluid flow is relatively weak.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2132-2139 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mathematical model is developed to describe the pit formation process in thin (∼0.1 μm) organic layers induced by short (〈100 ns), intense laser pulses. The basic premise is an ablation-driven viscous flow, in which the reactive pressure gradient due to polymer decomposition causes fluid motion. Contrary to the case of thick layers (∼1 μm) and long (∼500 ns), weak pulses, here surface tension gradients are shown to be too small to promote material flow in the short time span of laser exposure. The derived closed-form expressions for temperature profile and pit contour allow expedient calculation of threshold energies and prediction of functional relationships among imposed (e.g., pulse energy and width) and measured (e.g., pit width) system variables. Model predictions compare favorably with experimental observations of such interrelations.
    Type of Medium: Electronic Resource
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