Investigating the Potential of Using Focused Ion Beam Technology to Bore Holes in and Attach Fill-Tubes to a Beryllium Ablator

The current point design for ignition targets for the National Ignition Facility has a beryllium ablator. As Be is essentially impermeable to hydrogen, conceptually the shell will be filled by boring through the shell with a laser, then attaching a fill-tube. Examination of focused ion beam (FIB) technology is under way as an alternative to laser drilling. Holes of 40, 20, and 15 (mu)m diameter have been successfully ion milled through a 47 (mu)m thick Be layer. These holes are clean, though take several hours to make, and the geometry is limited by the aspect ratio of the depth to the diameter of the hole. Work was also done to investigate the possibility of using a FIB to create a counter-bore for the insertion and attachment of a fill-tube in a Be shell which has a pre-existing hole. Because the FIB can be controlled to submicron scales, the counter-bore can be easily centered on the through-hole and the side-walls and base of the counter-bore can be made very smooth. Finally, a proof-of-principle experiment was made to show that a Be wire could be attached to an in-situ micromanipulator and then be placed inside the counter-bore.