Improvement of Energy Resolution and Neutron–Gamma Discrimination of NaI:Tl,⁶Li Single Crystal Scintillators by Ca²⁺ and Sr²⁺ Co-Doping

Abstract

NaI:Tl,6Li single crystals, due to low use cost and an efficient gamma ray ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma$ </tex-math></inline-formula> ) and neutron ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> ) detection capability, have been regarded as promising <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n/\gamma $ </tex-math></inline-formula> scintillators. In this work, NaI:Tl,6Li single crystals co-doped with different Ca <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2+}$ </tex-math></inline-formula> and Sr <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2+}$ </tex-math></inline-formula> concentrations were grown by the multiampoule Bridgman method. Their <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray energy resolution and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n/\gamma $ </tex-math></inline-formula> discrimination were improved. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray energy resolution at 662 keV was improved from 7.0% to 6.0% by Ca <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2+}$ </tex-math></inline-formula> or Sr <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2+}$ </tex-math></inline-formula> co-doping, despite at the expense of scintillation yield by around 20%. The pulse shape discrimination (PSD), expressed as figure-of-merits (FoMs) for neutron and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray, was enhanced from 4.65 for NaI:Tl,6Li to 5.85 for Ca <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2+}$ </tex-math></inline-formula> co-doping and 5.72 for Sr <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2+}$ </tex-math></inline-formula> co-doping. This work not only highlights the effectiveness of the co-doping strategy on the improvement of NaI:Tl,6Li single crystal scintillator but also makes the crystal more competitive toward neutron and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray detection applications.

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