Microfabrication of hemispherical shells for laser fusion targets

Hemispherical shells for use in laser fusion targets have been fabricated by using reactive ion etching to produce a hemispherical original master pattern from a selected glass microsphere. Then micromolding techniques using silicone rubber and positive photoresist are employed to produce a large number of final molds which are coated with the shell material (parylene or copper). The flat background film is removed by a number of etching techniques and the final molds are dissolved to give free standing hemispherical shells. The shells were found to replicate the hemispherical section of the original microsphere within the measurement accuracy of about 3%. The advantages and current limitations of this technique are also discussed.