A Manufacturing Process for Precision Gold Support Rings for Laser Targets
A research effort performed by the Target Fabrication Group has developed a method for producing precision, meso-scale gold support rings for laser targets. Many different laser targets consist of planar components that are built upon a gold support ring, such as the HyDiv and RadG targets shown in Figure 1. Because of the sequence in which laser targets such as these must be built to achieve the required overall precision, the washer-shaped support rings must fit precisely onto fixtures that are used throughout the manufacturing process. Because the support ring is the fundamental structure onto which the target is built, any imprecision in the support ring propagates through the entire target. Thus, even if the physics performance of a laser target does not require a flat and precise support ring, the manufacturing methods used to achieve the overall level of precision demanded in the targets rely heavily on the precision of the support rings. Past efforts to purchase gold support rings from outside vendors have been either extremely costly, or the vendors were unable to deliver acceptable parts. On several occasions, difficulties in obtaining acceptable support rings in a timely manner have compromised the ability to manufacture and deliver targets in time for the shot dates. Because of the nature of laser target campaigns, where target designs are often finalized only a few months, or even weeks, before the shot date, it is often risky to rely on external vendors to supply these components. The risk can be eliminated with a manufacturing method that makes it reasonable to fabricate precision support rings ourselves. This document describes a manufacturing plan that was developed by the Target Fabrication Group for ''mass producing'' precision gold support rings that meet the requirements necessary for fabricating precise laser targets in a timely manner. Past efforts to manufacture or purchase precision support rings have met varying levels of success. Many laser target assemblies require rings made of pure gold with a thickness on the order of 100 {micro}m to 200 {micro}m. The support rings must be flat to within 2 {micro}m (flatness/diameter = 0.04%), and the inner diameter must be precise to within approximately 1 {micro}m to 2 {micro}m (0.02% to 0.04%). The two faces of the ring must also be parallel and be free of surface contaminants. One method of producing high-quality rings is to diamond turn each one individually from a bar of stock material. This method produces rings with adequate flatness and dimensional accuracy, but it requires a great deal of time, so it is very expensive and ties up fabrication resources for a prohibitively long period of time. Another method that yields high-quality support rings is to plate gold onto a diamond turned copper mold. When the copper mold is etched away, a freestanding ring is produced. This method is also extremely time intensive and expensive. Efforts at both LLNL and by external vendors have attempted to produce gold support rings using various combinations of laser machining, wire EDM, turning, double sided lapping, and grinding. However, none of these other efforts produced acceptable support rings; the rings either did not meet the size specifications, did not meet the flatness and/or thickness specifications, or had large burrs on the edges. Prior campaigns with HyDiv and RadG targets required that a separate fixture be custom fit to each ring, which consumed a great deal of machining resources and delayed the delivery of the completed targets. The new method developed in this research produces support rings using a combination of electroplating, diamond turning, milling, and etching. These support rings meet the specifications of 2 {micro}m flatness and 2 {micro}m precision in the inner diameter. Each batch of up to 100 precision support rings can be produced in a matter of days, and they are not limited to an axisymmetric shape. For example, support rings have been produced for EOS targets with an integral tab used for a mirror mount. Thus, this new method of producing support rings will not only increase the precision of the targets and eliminate potential compromises to their timely delivery, but it will also allow greater complexity in the design of target components.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15009804
- Report Number(s):
- UCRL-TR-202851; TRN: US200430%%1325
- Resource Relation:
- Other Information: PBD: 2 Mar 2004
- Country of Publication:
- United States
- Language:
- English
Similar Records
Targets for the National Ignition Campaign
Inertial Confinement Fusion Quarterly Report January-March 1999, Volume 9, Number 2