Douglas J. Hatch

BEST PRACTICE PROCEDURES FOR MAKING DIRECT DRIVE CYLINDRICAL TARGETS FOR STUDIES OF CONVERGENT HYDRODYNAMICS

Abstract The production of cylindrical targets involves numerous steps. These steps are shared in common with many other types of Inertial Confinement Fusion (ICF) targets but no other single target encompasses such a wide range of fabrication techniques. These targets consist of a large number of individual parts, virtually all fabricated from commercially purchased raw material. As an example, the polystyrene used is synthesized in house from purchased monomer material. This material must be polymerized, purified, characterized and put into solution before it is even first used in the making of a target. Because virtually every manufacturing and assembly process we currently use is involved in the production of these targets, this paper is written as a way documenting the methods used.

Improvements in ICF target fabrication through high precision assembly and nondestructive characterization

Current ICF and HED targets are fielded on Omega, Z, and Trident; future campaigns will also be fielded on NIF. NIF will field less than 2 shots per day. With such few experiments, target fabrication and alignment accuracy, enhanced metrology and advanced component machining will be even more important. Future target designs are also becoming more complex and more stringent in terms of both manufacturing accuracy and precision. Several steps have been taken to improve the fabrication and characterization of targets, such as instituting an automated assembly station with 3 μm tolerances, utilizing non-destructive characterization tools for rapid component metrology and target assembly, and advancing machining capabilities. Recapitalization of target fabrication infrastructure is continuous.

Recent Developments in Fabrication of Direct Drive Cylinder Targets for Hydrodynamics Experiments at the OMEGA Laser

Abstract Experimental campaigns are being conducted at the 60 beam OMEGA laser at the University of Rochester’s Laboratory for Laser Energetics to acquire data to validate hydrodynamic models in the high energy-density regime. This paper describes targets that have been developed and constructed for these experimental campaigns. Targets are 860 μm inner diameter by 2.2 mm length cylinders with 70 μm thick polymer ablator. On the ablator inner surface and located halfway along the axis of the cylinder is a 500 μm wide Al marker band. Band thicknesses in the range 8-16 microns are used. CH foam with densities in the range 30-90 mg/cc fills the inside of the cylinder. While these targets have been fabricated for years, several new improvements and features have recently been developed. Improvements include the use of epoxy instead of polystyrene for the ablator, and the use of electrodeposited Al for the marker band. A critical feature of the target is the surface feature that is placed on the marker band. Experiments are aimed at understanding the hydrodynamic behavior of imploding cylinders as a function of this surface feature. Recent development work has focused on production of engineered surface features on the target marker band. Using a fast tool servo on a diamond turning lathe, a wide range of specified surface features have been produced. This paper will address improvements to the cylinder targets as well as current development efforts.

Micromachining of inertial confinement fusion targets

Abstract Many experiments conducted on todays largest inertial confinement fusion drive lasers require target components with sub-millimeter dimensions, precisions of a micron or less and surface finishes measured in nanometers. For metal and plastic, techniques using direct machining with diamond tools have been developed that yield the desired parts. New techniques that will be discussed include the quick-flip locator, a magnetically held kinematic mount that has allowed the direct machining of millimeter-sized beryllium hemishells whose inside and outside surface are concentric to within 0.25 μm, and an electronic version of a tracer lathe which has produced precise azimuthal variations of less than a micron.

Fabrication of the 3.2 gram Pegasus-II aluminum liner and load components of the Liner Ejecta Experiment

Fabrication of the 3.2 gram Pegasus-II 1100 series aluminum liner is described. This liner is driven by nominally 5 MA from the Pegasus-II two-stage Marx bank charged to approximately 35 kV. The liner will accelerate symmetrically to a final velocity of 3 mm//spl mu/s while it remains in contact with an annular glide plane surface at each electrode for a radial distance of 7.5 mm. At this drive level, up to 300 kbar shocks are expected when the solid density liner wall collides with the surface of a cylindrical liner experiment assembly mounted on axis within the liner bore. Components of the Los Alamos Liner Ejecta Experiment are described as one example of a Pegasus-II liner experiment.