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Title: Foam mitigates key obstacle in quest for laser fusion

Abstract

No abstract prepared.

Authors:
Publication Date:
OSTI Identifier:
22597916
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics Today; Journal Volume: 69; Journal Issue: 6; Other Information: (c) 2016 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; FOAMS; OPTIMIZATION; THERMONUCLEAR REACTIONS

Citation Formats

Grant, Andrew. Foam mitigates key obstacle in quest for laser fusion. United States: N. p., 2016. Web. doi:10.1063/PT.3.3189.
Grant, Andrew. Foam mitigates key obstacle in quest for laser fusion. United States. doi:10.1063/PT.3.3189.
Grant, Andrew. 2016. "Foam mitigates key obstacle in quest for laser fusion". United States. doi:10.1063/PT.3.3189.
@article{osti_22597916,
title = {Foam mitigates key obstacle in quest for laser fusion},
author = {Grant, Andrew},
abstractNote = {No abstract prepared.},
doi = {10.1063/PT.3.3189},
journal = {Physics Today},
number = 6,
volume = 69,
place = {United States},
year = 2016,
month = 6
}
  • Recent experiments have shown that low density foam layers can significantly mitigate the perturbing effects of beam nonuniformities affecting the acceleration of thin shells. This problem is studied parametrically with two-dimensional LASNEX [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Controlled Fusion {bold 2}, 51 (1975)]. Foam-buffered targets are employed, consisting typically of 250 {Angstrom} of gold, and 50 {mu}m of 50mg/cm{sup 3} C{sub 10}H{sub 8}O{sub 4} foam attached to a 10 {mu}m foil. In simulation these were characteristically exposed to 1.2 ns, flat-topped green light pulses at 1.4{times}10{sup 14}W/cm{sup 2} intensity, bearing 30 {mu}m lateral perturbations ofmore » up to 60{percent} variation in intensity. Without the buffer layers the foils were severely disrupted by 1 ns. With buffering only minimal distortion was manifest at 3 ns. The smoothing is shown to derive principally from the high thermal conductivity of the heated foam. The simulation results imply that (1) the foam thickness should exceed the disturbance wavelength; (2) intensities exceeding 5{times}10{sup 13}W/cm{sup 2} are needed for assured stability beyond 2 ns; (3) longer foams at lower densities are needed for effective mitigation with shorter wavelength light; (4) the gold layer hastens conversion of the structured foam to a uniform plasma. {copyright} {ital 1998 American Institute of Physics.}« less
  • Examined has been the performance of cryogenic fuel loading into a spherical foam shell target for laser fusion program by means of thermal cavitation technique to nondestructively measure the loaded fuel mass {ital in} {ital situ}. Experimental results on the loaded mass by means of the thermal cavitation technique ranged from 95% to 135% of the fully saturated fuel mass, which was measured by the resonance elastic vibration technique. In order to discuss the variation in loaded fuel mass, we have analyzed the exact bridge profile formed between the shell and the liquid fuel surface and the capillary binding force.more » Sublimation of the loaded fuel before the laser irradiation is considered to achieve quantitatively controlled accurate fuel loading, including fuel shrinkage by phase changing and the incoming thermal radiation circumstantially.« less
  • A new technique to make low-density, low-atomic-number foam shells was developed for use in cryogenic laser fusion targets. Shells with sphericity {gt} 99% and wall uniformity {gt} 97% were fabricated by a density matched emulsion method using cross-linked copolymerization in the oil phase of the emulsion. The diameter, wall thickness and density of the shells ranged in 100--1500 {mu}m, 10--150 {mu}m, and 90--310 mg/cm{sup 3}, respectively. Some foam shells exhibited a membrane on the outer surface, which could be used as the protective layer to prevent liquid fuel from boiling off. The foam shell was transparent when it was saturatedmore » with liquid deuterium. This enables us to characterize distribution of the liquid fuel in the shell using an optical interference technique.« less
  • Spherical hollow polymer foam shells used as a sustainer of cryogenic fuel for the inertial fusion target have been developed. Foam shells which have 500--1000 {mu}m diameter with a 30--100 {mu}m uniform wall, 4 {mu}m cell size and 40 mg/cm{sup 3} density, have been fabricated using a dual-nozzle droplet generator and a freeze-dry technique. Requirements to obtain a uniform thick wall and fine cell size are discussed.
  • We have presented a novel {ital in} {ital situ} method which is simple and sensitive, to measure the micromass of the fuel layer in a cryogenic foam target. In this method, a foam shell is mounted on a flexible polyester fiber 7 {mu}m in diameter and 800 {mu}m in length. The fiber is suspended with a stalk which is mechanically vibrated at any given frequency. The resonant frequency of the elastic vibration of a foam-fiber system is measured before and after fuel loading. The mass of the fuel can be determined from the change in the resonance frequency in themore » range from submicrograms to submilligrams. The resolution of this system, which is limited by the {ital Q} factor of the foam-fiber system, is better than 0.2 {mu}g corresponding to the measurement accuracy of 0.1%.« less