Studies of Non-Proportionality in Alkali Halide and Strontium Iodide Scintillators Using SLYNCI
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1164-L07-04
Studies of Non-Proportionality in Alkali Halide and Strontium Iodide Scintillators Using SLYNCI Larry Ahle1, Gregory Bizarri2, Nerine J. Cherepy1, Woon-Seng Choong2, William W. Moses2, Stephan A. Payne1, Steven Sheets1, and Benjamin, W. Sturm1 1
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, U.S.A.
2
Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, U.S.A.
ABSTRACT Recently a collaboration of LLNL and LBNL has constructed a second generation Compton coincidence instrument to study the non-proportionality of scintillators [1]. This device, known as SLYNCI (Scintillator Light-Yield Non-proportionality Characterization Instrument), has an over 30 time higher data collection rate than previous devices enabling complete characterization of a sample with less 24 hours of running time. Thus, SLYNCI enables a number of systematic studies of scintillators as many samples can be processed in a reasonable length of time. The studies include difference in non-proportionality between different types of scintillators, different members of the same family of scintillators, and impact of different doping levels. The results of such recent studies are presented here, including a study on of various alkali halides, and the impact of europium doping level in strontium iodide. Directions of future work will also be discussed. INTRODUCTION The overall resolution of inorganic material used for radiation detection depends several factors including the efficiency for conversion of the electrons and holes into scintillation light. The efficiency for this process is not independent of energy deposited in the crystal which leads to a non-proportionality between energy deposited in the crystal and the light yield produced. This non-proportionality is often the limiting factor in determining the final resolution of the crystal. To measure this proportionality, a collaboration of LLNL and LBNL has constructed a second generation Compton coincidence instrument known as SLYNCI (Scintillator Light-Yield Non-proportionality Characterization Instrument) [1]. This instrument enables a complete nonproportionality measurement in less than 24 hours, thus making it more straight forward to make systematic studies of scintillator and non-proportionality. These studies include differences in non-proportionality between different types of scintillators, different members of the same family of scintillators, and impact of different doping levels. Such studies were performed for several alkali halides, strontium iodide, and lanthanum bromide. EXPERIMENT SLYNCI relies on Compton scattering events to measure the non-proportionality of a scintillator. It consists of a collimated 137Cs source, a PMT light detection from the scintillator being tested, and five HPGe detectors surrounding the scintillator. Gamma rays with energy of 661.660 keV from the 137Cs source are Compton scattered in the scintillator with the scattered photon being detected in one of the HPGe. The energy measured in th
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