Discrete layer verification of the LiF window spall diagnostic

Recently, LiF windows suspended close to the surface have been employed as a non-radiographic spall diagnostic. Calibration has typically used HE to shock metals to produce spall layers. Because the exact characteristics of these layers cannot be pre-determined, we are using a gas gun to test the accuracy and repeatability of the diagnostic. We impact a LiF or PMMA window in front of a VISAR probe with a projectile consisting of four thin stainless steel disks spaced apart 200 microns with either vacuum or polyethylene. The measured signature from the VISAR probe is compared with what is expected from the layered assembly traveling at the projectile's velocity