Ejecta transport, breakup and conversion

Abstract: 

We report experimental results from an initial study of reactive and nonreactive metal fragments ejecta transporting in vacuum, and in reactive and nonreactive gases.We postulate that reactive metal fragments ejected into a reactive gas, such as H2, will breakup into smaller fragments in situations where they are otherwise hydrodynamically stable in a nonreactive gas such as He . To evaluate the hypothesis we machined periodic perturbations onto thin Ce and Zn coupons and then explosively shocked them to eject hot, micron-scale fragments from the perturbations. The ejecta masses were diagnosed with piezoelectric pressure transducers, and their transport in H2 and He was imaged with visible and infrared (IR) cameras. Because Ce + H2 - CeH2 + Delta(H) , where H is the enthalpy of formation, an observed increase of the relative IR (radiance) temperature TR between the Ce-H2 and Ce-He gas systems can be used to estimate the amount of Ce that converts to CeH2 . The experiments sought to determine whether dynamic chemical eects should be included in ejecta-transport models.