Crystal growth and scintillation properties of Eu-doped Ca(BrxI1–x)2 crystals

• Published in: Radiation measurements 2019-08, Vol.127, p.106139, Article 106139
• Main Authors: Kamada, Kei, Iida, Takashi, Furuya, Yuki, Kim, Kyoung Jin, Yoshino, Masao, Murakami, Rikito, Shoji, Yasuhiro, Kochurikhin, Vladimir V., Yamaj, Akihiro, Kurosawa, Shunsuke, Ohashi, Yuji, Yokota, Yuui, Yoshikawa, Akira
• Format: Article
• Language: English
• Subjects: Halides; Nuclear applications; Optical properties; Single-crystal scintillators
• ISSN: 1350-4487; 1879-0925
• DOI: 10.1016/j.radmeas.2019.106139

In this study, solid solutions of Ca(Br,I)2 were prepared to mitigate the cleavage feature of CaI2. Samples were grown using the Bridgman–Stockbarger (BS) method in a quartz ampoule. Eu2+ 4f–5d emissions were observed, peaking at 462–464 nm with a scintillation decay time of around 1000–1500 ns. Eu2%:CaBr0.5I1.5 showed the best light output of 109,000 photons/MeV, and Eu2%:CaBrI showed the best energy resolution (7.9%@662 keV) among the crystals grown. Eu2%:CaBr0.5I1.5 showed the same crystal phase as CaI2 and a strong cleavage feature. In contrast, Eu2%:CaBrI did not exhibit the cleavage feature and was more feasible for mass production as a detector material. Eu-doped CaBrI was the most promising material, not only for applications in the observation of neutrinoless double beta decay, but also other high-energy physics, gamma ray surveys, and gamma camera applications, owing to the optimization of light yield and energy resolution without cleavage. •Eu doped CaBr0.5I1.5, CaBrI, and CaBr1.5I0.5 crystals were grown using the BS method.•There can be a chemical compound close to the 1:1 ratio between CaBr2 and CaI2.•Eu:CaBrI did not show cleavage feature.•Eu:CaBrI showed 71000 ph/MeV of light output and 1209ns of scintillation decay time.