Developing Quantum Levitation of ICF Capsules Coated with MgB2 Thin Films
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Current inertial confinement fusion (ICF) capsule support technologies create implosion perturbations which reduce fusion yield, driving the search for new support paradigms. Quantum levitation of the capsule will eliminate the requirement of a physical support structure, increasing fusion yield. The application of an external magnetic field to a capsule coated with a superconducting film can provide the necessary conditions for levitation. Magnesium diboride (MgB2) 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. This project is part of an ongoing effort which seeks to coat ICF capsules with a thin layer of superconducting MgB2. This project studied the synthesis of MgB2 and diffusion/reaction kinetics of B/Mg/B m ultilayer thin films. These films were sputter deposited on flat glassy carbon substrates. Films were annealed in a tube furnace at temperatures between 400 °C and 650 °C for a total of 29 hours with film characterization done at predetermined intervals. 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. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize surface morphology. Superconducting behavior was observed in thin films annealed at and above 450 °C. Formation of superconducting MgB 2 at 450 °C h as not been previously reported below 500 °C. The surface of the samples annealed at 500 °C and below was smooth with a measured roughness of ~3 nm. After 29 hours of annealing time, the 450 °C sample had a transition temperature of 27.3 K. The highest transition temperature measured was 30.9 K and was associated with a sample annealed for 29 hours at 650 °C. Transition temperatures were weakly positively correlated with annealing temperature and showed dependence on initial structural quality and oxygen contamination. Current research is attempting to synthesize superconducting MgB2 coatings on spherical Si beads with the findings of this study. Future efforts are focused on the construction and testing of a levitation apparatus.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1470705
- Report Number(s):
- LLNL-TR-758031; 946079
- Country of Publication:
- United States
- Language:
- English
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