Measuring bond strength of Capsule to Fill Tube Assembly (CFTA) at cryogenic temperatures

Recent unexpected failures of capsule to fill tube assemblies fielded for NIF have prompted a revisit to study the behavior of alterna ve glue op ons and surface pretreatments to increase adhesion strength and decrease failure.The bond strength of adhesives used in NIF targets have historically been tested by a lap sheer method on Instron.However, the behaviors of materials may differ when used in such small amounts as on a CFTA as well as at different temperatures.A method and fixturing has been developed to mount a CFTA to an Instron for more accurate measurements and the ability to cool the bond with liquid nitrogen.CFTAs with 2, 5, and 10 um diameter fill tubes have been tested at 20 C and -196 C. The CFTA bond has been measured to be stronger at cryogenic temperatures.This newly developed method has shown reproducible results for measuring the bond strength of NIF target CFTAs.