Portable Lead Iodide Environmental Monitor for Nuclear Radiation

Environmental monitoring of possible contamination by radioactive materials has created a need for portable measurement systems that can assay low-grade radioactive materials in waste and in process equipment. Currently available instruments for environmental radiation monitoring are either of poor spectrum resolution (NaI detector) or of limited portability (HP Ge). HP Ge detectors require large size cryogenic cooling and high voltage power supplies for operation, making the instruments bulky and cumbersome. In this proposal, we plan to fabricate lead iodide (PbI2) detectors for use in portable, lightweight radiation detection instruments for environmental monitoring and field application. PbI2, with its wide bandgap (2.5eV) and high Z elements (Pb=82, I=53) has ideal material characteristics. It makes possible radiation detectors that are small, sensitive, have good optical response, and operate at room temperature and higher temperature with bias voltages of a few or tens of volts. We have developed special techniques to prepare high quality crystals and to fabricate high performance X-ray and gamma-ray detectors consistently. Initial testing indicates that PbI2 detectors are sensitive to a wide range of radioactive sources, making them suitable for integration in instruments used in a variety of applications. Anticipated Benefits: PbI2 detector has the potential use for environmental monitoring and field measurements for radiation protection, nuclear materials control and waste management, nuclear arms regulation, X-ray astronomy for space exploration, X-ray fluorescense analysis. It has the potential to replace NaI scintillation and Ge radiation detectors in portable nuclear instruments. PbI2 may be a major breakthrough in high temperature detection of nuclear radiation.