Development of a dynamic spot size diagnostic for flash radiographic X-ray sources

There has been considerable work in recent years in the development of high-brightness, high-dose flash X-ray radiographic sources. Spot size is one of several parameters that helps characterize source performance and provides a figure of merit to assess the suitability of various sources to specific experimental requirements. Time-integrated spot-size measurements using radio-graphic film and a high-Z rolled-edge object have been used for several years with great success. The advanced radiographic technologies program thrust to improve diode performance requires extending both modeling and experimental measurements into the transient time domain. A new time resolved spot detector (TRSD) is under development to provide this information. In this paper we report the initial results of the performance of a 148-element scintillating fiber array that is fiber-optically coupled to a gated streak camera. Spatial and temporal resolution results are discussed and the data obtained from the Sandia national laboratories (SNL) RITS-3 (Radiographic Integrated Test Stand) accelerator are presented.