Inertial confinement fusion implosions using capsules with two concentric shells separated by a low density region (double shells) are reported which closely follow one dimensional (1D) radiatively ...driven hydrodynamics simulations. Capsule designs which mitigate Au M-band radiation asymmetries appear to correspond more closely to 1D simulations than targets lacking mitigation of hohlraum drive M-band nonuniformities. One capsule design achieves over 50% of the unperturbed 1D calculated yield at a convergence ratio of 25.5, comparable to that of a double-shell design for an ignition capsule at the National Ignition Facility.
Laser imprinting has been studied and, in particular, saturation of areal density perturbations induced by near single mode laser imprinting was observed. Several issues important for the foam ...buffered direct drive scheme have been investigated. These studies included measurements of the absolute levels of stimulated Brillouin and Raman scattering observed from laser irradiated low density foam targets, either bare or overcoated with a thin layer of gold. A novel scheme is proposed to increase the pressure in indirectly driven targets. By heating a foam supersonically that is attached to a solid target the pressure generated is not only the ablation pressure but also the combined pressure due to ablation at the foam-foil interface and the heated foam material. Planar brominated plastic foil targets overcoated with a low density foam were irradiated by a soft X ray pulse. The pressure was obtained by comparing the rear side trajectory of the driven target observed by soft X ray radiography with one dimensional radiation hydrodynamic simulations. Observations were also carried out of the transition from supersonic to subsonic propagation of an ionization front in low density chlorinated foam targets irradiated by an intense soft X ray pulse. The diagnostic for these measurements was K shell point projection absorption spectroscopy. In the fast ignitor area the channelling and guiding of picosecond laser pulses through underdense plasmas, preformed density channels and microtubes were investigated. It was observed that a large fraction of the incident laser energy can be propagated. Megagauss magnetic fields were measured, with a polarimetric technique, during and after propagation of intense picosecond pulses in preionized plasmas. Two types of toroidal fields, of opposite orientation, were detected. In addition, the production and propagation of an electron beam through solid glass targets irradiated at intensities above 10 super(19) W/cm super(2) were observed using optical probing techniques.
Micromachining of inertial confinement fusion targets Gobby, P.L; Salzer, L.J; Day, R.D ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/1997, Letnik:
397, Številka:
1
Journal Article
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Many experiments conducted on today's largest inertial confinement fusion drive lasers require target components with sub-millimeter dimensions, precisions of a micron or less and surface finishes ...measured in nanometers. For metal and plastic, techniques using direct machining with diamond tools have been developed that yield the desired parts. New techniques that will be discussed include the quick-flip locator, a magnetically held kinematic mount that has allowed the direct machining of millimeter-sized beryllium hemishells whose inside and outside surface are concentric to within 0.25 μm, and an electronic version of a tracer lathe which has produced precise azimuthal variations of less than a micron.
Targets for laser-driven opacity measurements Gobby, P.L; Bush, H; Gurule, V.A ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/1995, Letnik:
362, Številka:
1
Journal Article
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Special laser targets have been designed and fabricated which allow the opacity of materials to be experimentally determined at elevated temperatures (
kT ≤ 200 eV). A general description of the ...technique is presented, as well as the fabrication steps necessary to produce the targets. A uniform high temperature environment is provided by the use of small millimeter-sized hohlraums driven by the Nova laser at Lawrence Livermore National Laboratory. The material sample is placed within the hohlraum and is further illuminated by the X-rays produced by one or two of the Nova beams incident on a second material known as a back lighter. Thus far, silver and niobium opacity samples have been used, and each has required a different fabrication technique.
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