Growth of Large Diameter High-Purity Germanium Crystals for Nuclear Physics Research

DOE Nuclear Physics user facilities require larger high-resolution gamma-ray detector systems to provide higher sensitivity measurements. Large diameter germanium crystals are being grown, evaluated, and iteratively improved in the laboratory. Large-diameter crystals will be made into large segmented planar detectors to demonstrate the viability of the crystals and the advanced detection capabilities for DOE Nuclear Physics measurements. Numerous large germanium crystals were grown under varied thermal conditions to eliminate a severe crystallography problem previously observed in the crystals. Excellent gamma-ray energy spectroscopy and uniform impurity concentration were established. Numerous extremely large diameter germanium crystals will be grown using the thermal conditions developed during Phase I. The crystal properties will be fine-tuned to allow fabrication of 150-mm through 200mm diameter germanium detectors. Fully operational large-diameter segmented planar detector systems will be fabricated and evaluated as a demonstration of the technology. Commercial Applications and Other Benefits: In addition to immediate impact at DOE user facilities performing Nuclear Physics and rare-particle detection measurements, the detectors from these larger diameter germanium crystals will impact nuclear security, nuclear cleanup, and nuclear medicine. Molecular imaging in nuclear medicine represents the most significant commercial application. From growing the germanium crystal to constructing a final detector system, the manufacturing process will always require good scientists, engineers, technicians, and association with research scientists at DOE laboratories.