SCINT 2017 - 14th Int. Conference on Scintillating Materials and their Applications

Efficiency studies on Gd_3Ga_3Al_2O_12 scintillators: Simulations and measurements

21 Sept 2017, 10:00

1h

Congress Centre "Le Majestic"

Poster presentation P5_characterization Poster Session 3

Speaker

Ms Sheetal Rawat (Indian Institute of Technology, Roorkee)

Description

For $\gamma$-ray spectroscopy, apart from having high light output, good energy and timing resolution, it is the high efficiency (both detection and photo-peak) of the detector which is of paramount importance. The detection efficiency is a measure of the percentage of radiation that a given detector detects from the overall yield emitted from the source. In the category of inorganic scintillators, recently developed cerium doped Gd${}_3$Ga${}_3$Al${}_2$O${}_{12}$ (GGAG) not only has high density (6.7 g/cm${}^3$) and atomic number (55) but also has high light output (55,000 ph/MeV), nearly 6% (at 662 keV) energy resolution and 550 ps time resolution [1]. These properties make GGAG a suitable detector choice for many applications.

Several studies on efficiency measurements were made in the past with different types of scintillators. Melcher et al. [2] have measured photo peak efficiency of BGO and CdWO${}_4$ relative to NaI:Tl as 3.3 and 3.2 respectively. G. Anil Kumar et al. [3] have carried out detailed energy dependent studies of total detection (TDE) and photo peak (PE) efficiency of 1″$\times$1″ LaBr${}_3$ both experimentally and using GEANT4 simulation toolkit. In the present work, we have carried out detailed Monte Carlo simulations of absolute efficiency (both TDE and PE) of GGAG scintillators of different sizes for gamma rays up to energy of 5 MeV. Experimental measurements were also done to validate the simulation results.

A 18$\times$18$\times$10 mm${}^3$ GGAG:Ce crystal was mounted on a vertically setup Hamamatsu PMT. Sufficient layers of 0.1 mm thick teflon reflector was wrapped around the crystal and an optical grease was used to couple its polished surface to the PMT. We have used four gamma sources, namely, ${}^{137}$Cs (115 kBq), ${}^{134}$Cs (152 kBq), ${}^{60}$Co (104 kBq) and ${}^{22}$Na (60 kBq) for energy calibration and efficiency calibration. TDE and PE data was obtained by keeping ${}^{137}$Cs source above the detector assembly at various distances for the duration of 1000 s. After the background and dead time correction, TDE and PE at 662 keV for GGAG were measured to be (9.22±0.01)% and (3.87±0.01)% respectively. Whereas, simulated TDE and PE values were 10.53% and 3.92% respectively. These high efficiency values are in accordance to our estimation owing to crystal’s high density and atomic number.

References

1. Tyagi M. et al., Journal of Physics D 46, 2013, p. 475302.
2. Melcher C.L. et al., IEEE Transactions on Nuclear Science, vol. 36, 1989.
3. G. Anil Kumar et al., Nuclear Instrument sand Methods in Physics Research A 610, 2009, p. 522–529.

Presentation materials

SCINT poster2017_final_rawat.pdf