micron scale deep hole drilling for beryllium capsule fill applications

a laser processing system has been developed to drill high aspect ratio holes through the impermeable beryllium capsules envisioned for ignition shots on NIF.the drilling system was designed to produce holes with an entrance and exit diameter of approxiately 5(mu)m through the full 175(mu)m thickness of the capsule.to meet these reqirements a frequency doubled femtosecond class Ti:sapphire laser is directed through a high numerical aperture lens to provide the spot geometry needed to drill the hole.the laser pluse is confinded by the metallic walls of the hole.thereby maintaining the diameter of the channel well beyond the rayleigh range of the optical system.presented is the current state of this work-in-progress.including descriptions of the device and the tehcnique used to produce the holes.the varius means of characterizing the laser drilled channels are also discussed.