Use of flash X-radiography to observe ejecta from shaped charge penetrators in concrete

Abstract
This paper describes the use of Flash X-Radiography for imaging the ejecta cloud from a small-scale shaped charge jet impacting a semi-infinite concrete target. The aim is to understand the timescale and extent of the ejecta as well as measuring the general velocity field. This provides useful additional information for validating material and fracture models used in simulations. The technique required the novel use of the X-ray equipment, since it was necessary to image the ejecta cloud in a region just above the surface of the concrete target and to take two images very close together, to allow a reasonably accurate velocity measurement. Also the extent of the ejecta cloud was important in terms of determining whether it originated from the borehole or as a result of the surface spallation leading to crater formation. Various techniques of target doping were used and these had varying degrees of success since the doping method could also affect the borehole formation. These were compounded by limits in the resolution of the equipment. General results are presented and recommendations made for developing this promising technique further.