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Title: Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

Initially, the alkaline-earth scintillator, CaI 2:Eu 2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI 2:Eu 2+ has the potential to exceed the excellent scintillation performance of SrI 2:Eu 2+. In fact, theoretical predictions for the light yield of CaI2:Eu 2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI 2:Eu 2+ scintillator, the performance of CaI 2:Eu 2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI 2:Eu 2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI 2:Eu 2+ and pure CaI 2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI 2:Eu 2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on coolingmore » that would result in crystal cracking of the lamellar structure of CaI 2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI 2:Eu 2+ and un-doped CaI 2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI 2:Eu 2+ and pure CaI 2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1185906
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 786; Journal Issue: C; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Scintillator; crystal growth; Bridgman growth; CaI2:Eu; Plastic deformation