Laser Welding Micro-Holes in Beryllium Capsules*

In order to produce gas filled beryllium capsules for inertial confinement fusion (ICF) experiments, we are developing laser welding as a tool to seal micro-holes drilled through the capsule wall. Micro-holes of diameter 5 to 10~$\mu$m drilled through 100~micron thick cold rolled beryllium foils have been welded closed. Welds were tested to be leak tight with a helium leak detector. A windowed pressure chamber has been built to allow capsules to be welded while under a pressure of up to 30~atm. Cryocondensing fill gas into the capsules will potentially allow higher fill pressures. The current formulation of sputter-deposited beryllium used to produce capsules appears to be more susceptible to cracking than the cold-rolled beryllium foil. The progress on welding closed micro-holes in beryllium capsules made by sputter deposition will be presented.