High-Energy Gamma-Ray Calibration Source

No long-lived gamma-ray calibration sources exist with energies above 3.5 MeV, which is an impediment to the calibration of high-purity-germanium and scintillation detectors used in homeland security, nuclear physics and astrophysics. Recent advances in Prompt Gamma-ray Activation Analysis with guided neutron beams have led to the precise calibration of neutron-capture gamma ray sources with energies up to 10.8 MeV. In this project, these neutron-capture gamma ray sources will be produced in a moderator/transducer surrounding a compact, low-yield neutron generator that uses the safe D-D fusion reaction. In Phase I, a portable gamma-ray generator was designed using an inexpensive ion source, a self-replenishing target for generating neutrons, and a compact moderator with a gamma-ray transducer. The parameters for selecting the three major components were based on the required count rate for calibrating the frequency and efficiency of the detector, while still ensuring operator safety and minimizing possible damage to the detector. The high-energy gamma ray spectrum was measured using the selected transducer material. In Phase II, the ion source will be fabricated and tested, and the fast neutron generator will be fabricated and integrated into the moderator and gamma ray emitter. Then, the source¿s gamma-ray yield will be measured, and the source¿s safety and benefits for detector calibration will be determined. Commercial Applications and Other Benefits as described by the awardee: The DOE and the International Atomic Energy Agency must provide for the application of standards for the safety of nuclear installations and radioactive sources. The new device should enable the easy calibration of the energy and efficiency of HPGe detectors at high gamma ray energies, at in-house installations or in the field, for the identification of nuclear and radioactive materials. It also should reduce security concerns about the storage of radioactive sources currently in use.