Search

AbstractThe shear experiments are designed to investigate the transition to turbulence of the Kelvin-Helmholtz instability driven by counter-propagating shear flows. The shear targets for the National Ignition Facility (NIF) shear experiments consist of two hohlraums connected to both ends of a shock tube. The cylindrical shock tube is filled with two hemi-cylindrical CH foams separated by a metal tracer foil. On both ends, a thick gold half-moon–shaped D-plug is placed on opposite halves of the tube to create counter-propagating shock waves. The design is based on a smaller Omega shear target. While the basic NIF design has remained the same, details of the design have undergone several changes over the last 2 years and continue to evolve to improve the quality of the experimental results. Design changes include shock tube designs, tracer foil variations, transitioning to beryllium spool machining, and groove features inside of the tube. Details of how the targets are built including design, machining the parts, target assembly, and metrology are presented, as well as recent target developmental work to meet the needs of future experiments and to improve target assembly efficiency and accuracy.

AbstractAt the University of Michigan (U-M), we have successfully fabricated and characterized targets for our experimental campaigns since 2003. Because of the unique production environment, we iterate many models in the course of a single-shot plan and have the flexibility to test and alter target designs as needed throughout the build process. Over the past few years, many advances in target design and fabrication have allowed greater degrees of design complexity while retaining the high level of build precision necessary for microscale experiments on facilities such as the OMEGA laser. Extensive target metrology is carried out during and after the fabrication process to allow for full knowledge of experimental conditions and to ensure that all targets are within required specifications. Analysis of the variability in metrology measurements over the multiple-shot campaigns allows for the quantification of improvements in the target build quality and metrology measurements. We present a summary of the capabilities and recent developments of target fabrication at U-M, as well as progress and analysis of build repeatability.