New cerium-activated phosphate glass scintillators
L. A. Boatner, D. Wisniewski, John S. Neal, Joanne O. Ramey, and
G. E. Jellison
Center for Radiation Detection Materials and Systems, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831
Early research on new high-durability glasses for nuclear waste disposal revealed that the addition of iron to lead-pyrophosphate-based glasses resulted in an increase in the glass chemical durability by a factor of ~104 [1]. Subsequent work led initially to the development of new colorless, high-durability phosphate optical glasses via the addition of indium or scandium to lead pyrophosphate [2,3] and, ultimately, to the development of calcium-sodium phosphate optical-fiber cladding glasses [4]. We have investigated the applicability of these and other related types of phosphate glasses as host systems for the formation of cerium-activated gamma-and x-ray scintillators. The melting and pouring temperature of ~1050oC for these phosphate glasses is significantly lower than the processing temperatures generally associated with the formation of silicate glass scintillators, and additionally, our work has shown that the cerium 3+ activator ion can be easily added in the form of CeCl3. The calcium-sodium phosphate glasses will tolerate relatively high cerium concentrations based on the initial melt compositions, and the light yield for gamma-ray excitation at 662 keV was determined as a function of cerium concentration up to the saturation level. The Ce-activated Ca-Na phosphate glass primary component decay time was in the range of 30 to 40 nsec for various Ce concentrations with the contribution of the light output of the primary component ranging from 75 to 90%. Studies of the effects of co-doping with both Ce and Gd were carried out in the case of the Ca-Na phosphate glass hosts. The effects of post-synthesis thermochemical treatments in a variety of atmospheres and at various processing temperatures were also investigated for the Ce-activated Ca-Na phosphate scintillators. Research carried out in the Center for Radiation Detection Materials and Systems at ORNL is supported by the NNSA Office of Nonproliferation Research and Engineering (NA-22), USDOE and by the U. S. Department of Homeland Security, Domestic Nuclear Detection Office.
*corresponding author e-mail:
References
1. B.C.Sales and L.A.Boatner, “Lead-Iron Phosphate Glass: A Stable Medium for High-Level Nuclear Waste,” Science 226, (4670) 45–48 (1984).
2. B.C.Sales and L.A.Boatner, “Optical, Structural, and Chemical Characteristics of Lead-Indium Phosphate and Lead-Scandium Phosphate Glasses,” J. Am. Ceram. Soc. 70, (9) 615–621 (1987).
3. K.Suzuya, C.K.Loong, D.L.Price, B.C.Sales, and L.A.Boatner, “The Structure of Lead-Indium Phosphate and Lead-Scandium Phosphate Glasses,” J. NonCryst. Solids 258, 48–56 (1999).
4. U.S.Patent No. 5,812,729, “Very High Numerical Aperture Light Transmitting Device,” coinventors S.W.Allison, L.A.Boatner, and B.C.Sales, issued September 22, 1998.