Elsevier

Radiation Measurements

Volume 56, September 2013, Pages 94-97
Radiation Measurements

Scintillation response of Y3Al5O12:Pr3+ single crystal scintillators

https://doi.org/10.1016/j.radmeas.2013.04.013Get rights and content

Highlights

  • Pr-concentration dependence of light yield in YAG:Pr crystals is studied.

  • Concentration quenching is revealed in 4f–4f emission spectra and decays.

  • Light yield of 15,600 ph/MeV & energy resolution of 6.4% @662 keV are evaluated.

  • Photofraction in pulse height spectra of 320 and 662 keV γ-rays is determined.

Abstract

In this paper we present the photoluminescence (PL) and scintillation response of Pr3+-doped Y3Al5O12 (YAG:Pr) single crystals grown by the Czochralski method with different Pr3+ concentrations of 0.16, 0.33, and 0.65 mol%. PL spectra and decay curves were measured for both the fast 5d → 4f and slow 4f → 4f emissions. The PL decay times were evaluated which evidence concentration quenching especially in 1D2 → 3H4 emission for the highest Pr3+ concentration. Light yield (LY) of 15,600 photons per MeV and energy resolution of 6.4% at 662 keV γ-rays were obtained with the YAG:Pr (0.33%) crystal. The LY non-proportionality and energy resolution versus γ-ray energy were measured and the intrinsic resolution was calculated. A good proportionality of the LY was found within 7% over the energy range from 1274.5 keV down to 32 keV. The estimated photofraction in the pulse height spectra of 320 and 662 keV γ-rays was also determined and compared with the theoretical one calculated using WinXCom program.

Introduction

Single crystal scintillators are widely used for the detection of ionizing radiation in nuclear and high energy physics, modern medical imaging, space exploration and industry. The fast and efficient 5d → 4f luminescence of Ce3+ makes it an effective emission center in scintillator applications. Therefore, Ce3+-doped inorganic scintillators such as e.g., Y3Al5O12:Ce (YAG:Ce) (Moszynski et al., 1994), Lu2SiO5 (LSO:Ce) (Melcher and Schweitzer, 1992), (Lu,Y)2SiO5:Ce (LYSO:Ce) (Cooke et al., 2000), Lu3Al5O12:Ce (LuAG:Ce) (Nikl et al., 2000) and LuYAlO3:Ce (LuYAP:Ce) (Drozdowski et al., 2006) have been intensively studied.

Pr3+-doped Lu3Al5O12 (LuAG:Pr) single crystal was reported as a fast and efficient scintillator (Nikl et al., 2005; Ogino et al., 2006). Pr3+-doped Y3Al5O12 (YAG:Pr) single crystal with a high light yield of about 300% with respect to Bi4Ge3O12(BGO) and a short decay time of about 18 ns was reported (Drozdowski et al., 2005). Recently, YAG:Pr with a prospective light yield comparable to LuAG:Pr (about 160% of BGO) and a fast scintillation response dominated by a 17 ns decay time was also reported (Pejchal et al., 2009).

In this work we studied a set of YAG:Pr crystals grown by the Czochralski method as for their photoluminescence (PL), radioluminescence (RL) spectra and PL decay. Furthermore, pulse height spectra were performed to evaluate light yield (LY), its non-proportionality and energy resolution. The estimated photofraction in the pulse height spectra of 320 and 662 keV γ-rays was also determined and compared with the ratio of the cross-sections for the photoelectric effect to the total one (WinXCOM program).

Section snippets

Experimental

YAG:Pr single crystals grown in the same batch by Czochralski method from 5N raw Y2O3, Al2O3 powders and 4N Pr6O11 one were produced by Crytur Ltd. in Czech Republic. Pr concentration of 0.16, 0.33, and 0.65 mol% in the crystal was determined by the wavelength dispersive X-ray fluorescence (WDX) method using RFA Philips PW 2400 apparatus at L-alpha line of Pr. For quantitative measurement the calibration set of mixed Y2O3, Al2O3 a Pr6O11 powders was prepared. We estimate the detection limit at

Luminescence characteristics

In Fig. 1 the PL spectra of YAG:Pr crystals are given together with the absorption spectrum for 0.16% Pr sample in the inset. The absorption bands at 240 and 290 nm can be attributed to the two lowest 4f(3H4) → 5d2,1 transitions of Pr3+. Week Pr3+4f → 4f transitions between 450 and 490 nm (3H4 → 3Px,1I6) and around 609 nm (3H4 → 1D2) were also observed in the absorption spectrum. Excitation within the 4f → 5d1 absorption band results in the dominant emission at 318 nm with a shoulder at 380 nm,

Conclusion

The luminescence and scintillation properties of YAG:Pr crystals grown by the Czochralski method were investigated. YAG:Pr exhibits a dominant emission peak at 318 nm with a shoulder at 380 nm under UV and X-ray excitations with a fast PL decay time of about 15 ns based on 5d1 → 4f transition of Pr3+. It shows integral scintillation efficiency of about 400% of that of the BGO. The YAG:Pr (0.33%) sample exhibits a high LY of 15,600 ph/MeV and a good energy resolution of 6.4% in a pulse height

Acknowledgments

This work was supported by the National Research University Project of Thailand's Office of the Higher Education Commission. Financial support of Czech GACR P204/12/0805 project is also gratefully acknowledged.

References (15)

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