Multi-MeV Flash Radiography in Shock Physics Experiments: Specific Assemblages of Monolithic Scintillating Crystals for Use in CCD-Based Imagers

We have developed a new CCD-based radiographic camera called CrystalEyeCam for use in shock physics experiments: it is composed of two turning mirrors and an objective to relay the (visible) image from a scintillator assembly to a highly sensitive, low noise CCD camera. The objective was specifically developed to match our needs and has few chromatic and geometric aberrations and high photometric performance. The scintillator assembly is constructed using a specific (patented) technique of assembling monolithic scintillating crystals. It replaces the segmented scintillator previously used at our facility and produces higher quality images (better resolution and no segmentation). The sensitivity, noise level, detection threshold and resolution of CrystalEyeCam were measured using an 18-MeV-bremsstrahlung spectrum, filtered with 10 cm of lead, and two 165 mm×165 mm BGO assemblies: 20 and 30 mm in thickness, respectively. In particular, with the 30 mm-thick BGO assembly, the measured detection threshold of the imager (at SNR0=2) is 1 μGy(air) and its resolution is ~1 mm. For 4-MeV incident photons, the estimated (energy) stopping power of the scintillator is 41%. The scintillator assembly thus proved to be a cheaper, effective alternative to segmented scintillators for use in CrystalEyeCam.