A High Sensitivity Gamma Ray Imager (HiSGRI) Based on Wavelength-Shifting Fiber Readout of LaBr3 Scintillators

Cerium-doped lanthanum bromide offers increased light yield and peak emission at shorter wavelengths compared to standard inorganic scintillators such as NaI or CsI. As a result, lanthanum bromide scintillators can be used as the basis of large scale hard X-ray/gamma ray imaging systems. By coupling a Ce:LaBr 3 scintillator with orthogonal layers of wavelength-shifting fibers viewed by multianode photomultiplier tubes to provide x-y position together with an Anger camera array of large area photomultiplier tubes to measure energy, a detector can be constructed with millimeter-scale position resolution and energy resolution only somewhat less than that obtained with bulk scintillators. We present measurements of the light yields and position resolution achievable with such a system.