A major challenge of the inertial confinement fusion (ICF) campaign is implosion perturbation due to fuel capsule support. In the current approach, a capsule is sandwiched between two thin, polymeric films (tents) to hold it inside a hohlraum. Variants of thin fibers have also been used to hold the capsule in some target designs. However, both tents and fibers cause strong implosion perturbations. Holding the capsule inside the hohlraum by levitation eliminates perturbation-causing mechanical support, making levitation an ideal solution.
Our research demonstrated a path to such an ideal capsule-support solution based on quantum (superconducting) levitation. In our approach, the outer surface of the capsule is coated with a thin (~ 100 nm) superconducting layer of MgB2, which is currently the most promising superconducting material candidate for this application. Magnetic coils outside the hohlraum levitate and position the capsule in the center of the hohlraum. In this work, we 1) developed and demonstrated a method for the deposition of smooth and uniform thin films of MgB2 on ICF-scale spherical capsules, 2) improved understanding of the effects of film thickness, interfaces, and lattice defects on the superconducting properties of MgB2, 3) performed cryogenic levitation experiments, and 4) developed a levitation model.
Our research leveraged Lawrence Livermore National Laboratory's core competencies in advanced materials and manufacturing. The results support advancements in the Laboratory's ICF campaign, ultimately ensuring the safety, security, and reliability of the nuclear deterrent. Our work also expands capabilities in high-energy-density physics capabilities and expertise in thin-film-superconductor-based devices.
Baker, A. 2018. "Non-Epitaxial Magnesium Diboride Films on Glassy Carbon Substrates." 2018 Spring MRS Meeting. Phoenix, AZ., April 2018. LLNL-PRES-748677.
Baker, A., et al. 2018. "Vapor Annealing Synthesis of Non-Epitaxial MgB2 Films on Glassy Carbon." Superconductor Science and Technology, 31, 055006. doi: 10.1088/1361-6668/aab4eb. LLNL-JRNL-743108.
——— . 2019. "Control of Superconductivity in MgB2 by Ion Bombardment." J. Phys. D, 52, 295302. LLNL-JRNL-763-060.
Bayu Aji, L., et al. 2018. "Degradation of Ultra-Thin Boron Films in Air." Applied Surface Science, 448, 498-50. doi: 10.1016/j.apsusc.2018.04.126. LLNL-JRNL-744456.
——— . 2019. "Solid-Phase Reactive Inter-Diffusion of Mg/B Multilayers." Journal of Applied Physics, 125, 075306. LLNL-JRNL-761423.
Kucheyev, S. 2017. "Quantum Levitation of Fuel Capsules". LLNL-PRES-736472.
——— . 2018. "Radiation Defect Dynamics Studied by Pulsed Ion Beams." VSE Technical Symposium. Beverly, MA. May 2018. LLNL-PRES-750363.
——— . 2018. "Recent Developments in Materials Science for Laser Targets At LLNL." 2018 Target Fabrication Workshop (TFW-2018), Darmstadt, Germany, September 2018. LLNL-PRES-758108.
——— . 2018. "Toward Quantum Levitation of Thermonuclear Fusion Fuel Capsules." Target Fabrication Meeting (TFM-2019), Annapolis, MD, April 2019. LLNL-PRES-772086.
Smalyuk, V., et al. 2018. "Review of Hydro-Instability Experiments with Alternate Capsule Supports in Indirect-Drive Implosions on The National Ignition Facility." Physics of Plasmas 25, 072705. LLNL-JRNL-750300.
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