Design Optimization of a Gamma-Ray Target for Replacement of Radionucleotides in Industrial Applications

The development of a gamma ray source, the Gamma Ray Non-proliferating Irradiator Technology (GRANIT), is under way at UCLA to replace Cs-137, a dangerous radioactive material, in oil well logging and other industrial processes.  This presentation focuses on the design of the gamma ray converter target within the GRANIT.  The target takes accelerated electrons and converts them into high-energy photons through a process called bremsstrahlung.  G4Beamline, a simulation toolkit (based on the Geant4 framework)—a Monte Carlo particle transport code—is used to simulate the gamma ray production process.  The target thickness and materials are optimized by analyzing different characteristics such as the energetic efficiency, average gamma ray energy, and the overall gamma ray energy spectrum.  The main material for the target will be tungsten due to its high radiative yield.  Using a 1.5MeV electron beam, the optimum thickness of a single-material tungsten target is approximately 0.18mm.  The results of these parametric studies is presented along with future plans to simulate and fabricate a multi-material target.