Fusion Science and Technology / Volume 55 / Number 4 / May 2009 / Pages 499-504
Technical Paper / Eighteenth Target Fabrication Specialists' Meeting
Experiments on the Omega laser at the Laboratory for Laser Energetics require tantalum oxide (Ta2O5) aerogel thin films with a thickness ranging from 70 to 150 m and densities of 250 and 500 mg/cm3. Experiments have been done with the aerogel in a disk geometry with diameters ranging from ~2 to 3 mm with annular slots machined into it and without the slots. These experiments place demanding specifications on the targets in terms of thickness, dimensionality, and mass density variation. Future radiation experiments at the National Ignition Facility will require larger targets ~7 mm in diameter and 200 m thick with more complex features. In the past these targets have been conventionally machined from a starting billet of aerogel ~5 mm in diameter and height. Through a series of steps the aerogel was eventually machined down to the desired thickness. This was a long and arduous labor-intensive process that had high attrition rates and an overall yield of ~50%. We have improved this process by developing a new fabrication technique involving casting the foam to the desired thickness and then laser processing to create the desired features. This technique yields targets that meet the demanding specifications used in recent experiments while increasing throughput, yield, and available feature complexity in targets.