The surface of the samples annealed at 500 ☌ and below was smooth with a measured roughness of ~3 nm. Formation of superconducting MgB 2 at 450 ☌ h as not been previously reported below 500 ☌. Superconducting behavior was observed in thin films annealed at and above 450 ☌. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize surface morphology. At each interval, superconducting properties of the samples were evaluated with superconducting quantum interference device (SQUID) magnetometry, while Rutherford backscattering (RBS) with 2 MeV 4He + ions was done to determine the composition and depth profile of the films. Films were annealed in a tube furnace at temperatures between 400 ☌ and 650 ☌ for a total of 29 hours with film characterization done at predetermined intervals. These films were sputter deposited on flat glassy carbon substrates. This project studied the synthesis of MgB 2 and diffusion/reaction kinetics of B/Mg/B m ultilayer thin films. This project is part of an ongoing effort which seeks to more » coat ICF capsules with a thin layer of superconducting MgB 2. Magnesium diboride (MgB 2) is an attractive option for ICF applications as it has a high reported superconducting transition temperature of 39 K and is a low Z compound. The application of an external magnetic field to a capsule coated with a superconducting film can provide the necessary conditions for levitation.
Quantum levitation of the capsule will eliminate the requirement of a physical support structure, increasing fusion yield. « lessĬurrent inertial confinement fusion (ICF) capsule support technologies create implosion perturbations which reduce fusion yield, driving the search for new support paradigms. In conclusion, the effects of x-ray shadowing during the drive and oxygen-induced perturbations during target assembly produced additional seeds for instabilities and were also measured in these experiments. Based on these experiments, 30-μm thick fill tubes and 300-μm offset cantilevered fill tubes were recommended for further tests using layered deuterium-tritium implosions. The cantilevered fill tubes were supported by 12-μm thick SiC rods, offset by 100 μm, 200 μm, and 300 μm from the capsule surfaces. In other experiments, the perturbations from cantilevered fill tubes were measured and compared to the tent perturbations. Subsequent experiments with 3-D perturbations have studied instability growth of 10-μm and 30-μm thick fill tubes to compare them with 30-nm thick tent perturbations at convergence ratios up to ~3. It was calibrated using hydrodynamic growth measurements of pre-imposed capsule modulations with Legendre modes of 60, 90, 110, and 140 at convergence ratios up to ~2.4.
A new “sub-scale” version of the existing x-ray radiography platform was more » developed for measuring growing capsule perturbations in the acceleration phase of implosions. After it was recognized that the tents had a significant impact of implosion stability, new support methods were investigated, including thicker, 30-μm diameter fill tubes and cantilevered fill tubes, as described in this article. In NIF implosions, the capsules are supported by tents because the nominal 10-μm thick fill tubes are not strong enough to support capsules by themselves. Hydrodynamic instability growth of the capsule support membranes (or “tents”) and fill tubes has been studied in spherical, glow discharge polymer plastic capsule implosions at the National Ignition Facility (NIF). The mass flux uniformity varied by 50% over the surface of a capsule and varied by 80% over the surface of the bounced pan.
The resulting mass-flux distribution to, and around, a capsule quantified the uniformity of the deposition process. The experimentally measured evaporation mass flux of the monomers resulted in a calculated pressure that corresponded to the measured actual value.
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