Abstract
A deuterium-ice extruder has been developed for inertial confinement fusion experiments on the Sandia National Laboratories Z Facility. The screw-driven extruder is filled via desublimation, where a slow flow of deuterium gas enters the extruder cavity and freezes to the walls without entering the liquid phase. Ice generated in this manner is optically clear, demonstrating its high uniformity. When the extruder cavity is filled with ice, the screw is driven downward, closing off the gas-fill line. With the ice cavity isolated, further screw rotation compresses the deuterium through a nozzle, extruding a fiber. Fiber diameters ranging from 200 to 500 µm have been extruded to lengths of 1.5 feet before hitting the vacuum chamber floor. The fiber straightness improves with the nozzle length-to-diameter aspect ratio. Deuterium-ice fibers can persist in high vacuum for more than 10min before breaking free from the nozzle. The peripheral infrastructure required for Z experimental operations is under development. An in-vacuum stepper-motor-based drive system will allow remote operation, and a translating cathode will ensure proper placement of the fiber in the powerflow hardware.
Highlights
Dense deuterium and deuterium–tritium (DT) fuels are used in a range of thermonuclear fusion platforms
Target concepts include dense deuterium arranged in the form of a single currentcarrying fiber,15–18 cylindrical arrays of thin wires, or a cylindrical shell
The drive screw is manually rotated. This is allowed by coupling the extruder assembly to a rotary vacuum feedthrough (RVF)
Summary
Dense deuterium and deuterium–tritium (DT) fuels are used in a range of thermonuclear fusion platforms. The central hot plasma can burn into the dense outer layer, greatly increasing the fusion yield (similar to laser-driven ICF fuel configurations). The high level project deliverable was to increase the available design space for novel target concepts through the development of three technologies: (1) a deuterium-ice extruder, (2) systems or methods for generating millimeter(s) thick cylindrical ice shells within cylindrical liners, and (3) an ice desublimation system for generating 10–100 μm layers of deuterium ice for metallicwall mix mitigation. VII, ongoing work to develop the peripheral infrastructure required for Z experimental operations will be discussed This includes development of an in-vacuum stepper-motor-based drive system to allow remote operation and a translating cathode to ensure proper placement of the fiber in the Z Facility powerflow hardware
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