Growth of inch-sized KCa0.8Sr0.2I3:Eu2+ scintillating crystals and high performance for gamma-ray detection

Abstract

A quaternary iodide KCa_0.8Sr_0.2I₃:Eu²⁺ scintillator with 2.5% energy resolution at 662 keV in a 5 mm³ sample shows great potential for use in gamma-ray spectroscopy applications. In this work, we report the state-of-the-art growth of high quality 25, 38, and 50 mm diameter KCa_0.8Sr_0.2I₃:Eu²⁺ single crystals by the vertical self-seeding Bridgman method. KCa_0.8Sr_0.2I₃:Eu²⁺ with a size of ∅25 mm × 25 mm can achieve excellent energy resolutions of 3.15% at 662 keV and 6.8% at 122 keV irradiation, which are superior to that of a commercial NaI:Tl⁺ of the same size. The nonuniformity of light collection and production in ∅25 mm × 25 mm and ∅38 mm × 38 mm KCa_0.8Sr_0.2I₃:Eu²⁺ crystals was evaluated by using a technique based on a collimated ¹³⁷Cs source and coupling the crystal to a photomultiplier tube (PMT) in different directions. The performances of the packaged crystals for practical use were also measured.