BaBrI:Eu crystals is a promising material for gamma-rays detection with light output > 100000 ph/MeV and the energy resolution of ~ 2.6% at 662 keV. This parameters are qualitatively better than conventional ones in conventional detectors based on NaI:Tl and CsI:Tl [1].

Typically, hygroscopic alkali earth iodide crystals are grown by the Stockbarger method in evacuated ampoules. Diameter of BaBrI crystals is limited by the ampoule size, and on practice it does not exceed 30 mm. Furthermore, BaBrI crystals often crack due to adhesion of crystals to the ampule walls, which induces mechanical stresses in crystals. Czochralski method can be appropriate to avoid cracking, because crystal grows in free geometry without contact to the crucible or thermal insulation.

This work is devoted to BaBrI crystal growth by the Czochralski method. Undoped BaBrI crystals with the diameter up to 2" were obtained. Samples for measuring the optical transmission spectra in the infrared, visible and ultraviolet ranges were cut from grown crystals. Correlation between growth conditions and luminescence properties was studied. The results are shown in Fig. 1 and 2.

Intensity of absorption band near ~1420 cm^-1 attributed to carbonate ions is significantly changes from sample to sample and clearly linked to difference in growth conditions (Fig. 1).

Photoluminescence spectra and scintillation properties of BaBrI(1) crystal excited at the fundamental absorption edge has a wide maximum near 450 nm and corresponds to the literature data [1]. At the same time, BaBrI(2), sample shows two luminescence bands near 410 nm and 550 nm. The second one is likely associated with presence of intrinsic or impurity defects (Fig. 2).

Fig.1 IR-transmission spectra of crystals sealed       Fig.2 Luminescence spectra of crystals.  in container with ZnSe windows.                                                    

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1. Optimization of bottom heater parameters at growth of large BGO crystals by conventional czochralski method
2. Optimization of bottom heater parameters at growth of large BGO crystals by conventional Czochralski method
3. Czochralski growth of 2" BaBrI crystals
4. Light yield behavior in mixed oxide scintillation crystals