Scratch Reduction in Polystyrene Beads and Capsules via Alternative Flask Material Testing
Not provided.
Nuclear Science & Technology↗
Engineering topics
Sweet, W.
Publications and source records attributed to Sweet, W..
Development of an x-ray radiography platform to study laser-direct-drive energy coupling at the National Ignition Facility
A platform has been developed to study laser-direct-drive energy coupling at the National Ignition Facility (NIF) using a plastic sphere target irradiated in a polar-direct-drive geometry to launch a spherically converging shock wave. To diagnose this system evolution, eight NIF laser beams are directed onto a curved Cu foil to generate Heα line emission at a photon energy of 8.4 keV. These x rays are collected by a 100-ps gated x-ray imager in the opposing port to produce temporally gated radiographs. The platform is capable of acquiring images during and after the laser drive launches the shock wave. A backlighter profile is fit to the radiographs, and the resulting transmission images are Abel inverted to infer radial density profiles of the shock front and to track its temporal evolution. Here, the measurements provide experimental shock trajectories and radial density profiles that are compared to 2D radiation-hydrodynamic simulations using cross-beam energy transfer and nonlocal heat-transport models.
47 OTHER INSTRUMENTATION↗
High-yield magnetic recoil neutron spectrometer on the National Ignition Facility for operation up to 60 MJ
We report that recent progress at the National Ignition Facility (NIF), with neutron yields of order 1 x 10 17 , places new constraints on diagnostics used to characterize implosion performance. The Magnetic Recoil neutron Spectrometer (MRS), which is routinely used to measure yield, ion temperature (T ion ), and down-scatter ratio (dsr), has been adapted to allow measurements of dsr up to 5 x 10 17 , and yield and T ion up to 2 x 10 18 in the near term with new data processing techniques and conversion foil solutions. This paper presents a solution for extending MRS operation up to a yield of 2 x 10 19 (60 MJ) by moving the spectrometer outside of the NIF shield wall. This will not only enhance the upper yield limit by 10x but also improve signal-to-background by 5x.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Machine Learning Algorithms for Automated NIF Capsule Mandrel Selection
Small shells, approximately 2 mm in diameter, made from Poly(α-methylstyrene) (PAMS) are used as mandrels in the production of glow discharge polymer capsules located at the center of inertial confinement fusion experiments. The visual inspection process of microscope images of these shell mandrels, including detection of micron-sized defects on the shell surface as well as the handling and sorting, is a very labor-intensive, repetitive, and highly subjective process that stands to benefit greatly from automation. As part of an effort to decrease the number of labor hours spent in capsule handling, inspection, and metrology, the development of robotic systems was presented in a paper by Carlson et al., “Automation in Target Fabrication” [Fusion Sci. Technol., Vol. 70, p. 274 (2016)]. The current work expands the automated image acquisition systems developed previously and adds the use of convolutional neural networks to select capsules best suited for use in the downstream production process. Through the use of these machine learning algorithms, the selection process becomes robust, repeatable, and operator independent. Finally, as an added benefit the system developed as part of this work is able to provide defect statistics on entire shell batches and feed this information upstream to the production team.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗