Absolute Luminescence Efficiency of Europium-Doped Calcium Fluoride (CaF2:Eu) Single Crystals under X-ray Excitation

Konstantinos Ninos,Nektarios Kalyvas,Ioannis Sianoudis,George Fountos,Christos Michail,Athanasios Bakas,George Panayiotakis,Ioannis Valais,Ioannis Kandarakis

doi:10.3390/cryst9050234

Konstantinos Ninos, Nektarios Kalyvas + Show 7 more

Open Access

https://doi.org/10.3390/cryst9050234

Copy DOI

Journal: Crystals	Publication Date: May 1, 2019
Citations: 26	License type: CC BY 4.0

Affiliation: University of West Attica, University of Patras

Abstract

The absolute luminescence efficiency (AE) of a calcium fluoride (CaF2:Eu) single crystal doped with europium was studied using X-ray energies met in general radiography. A CaF2:Eu single crystal with dimensions of 10 × 10 × 10 mm3 was irradiated by X-rays. The emission light photon intensity of the CaF2:Eu sample was evaluated by measuring AE within the X-ray range from 50 to 130 kV. The results of this work were compared with data obtained under similar conditions for the commercially employed medical imaging modalities, Bi4Ge3O12 and Lu2SiO5:Ce single crystals. The compatibility of the light emitted by the CaF2:Eu crystal, with the sensitivity of optical sensors, was also examined. The AE of the 10 × 10 × 10 mm3 CaF2:Eu crystal peaked in the range from 70 to 90 kV (22.22 efficiency units; E.U). The light emitted from CaF2:Eu is compatible with photocathodes, charge coupled devices (CCD), and silicon photomultipliers, which are used as radiation sensors in medical imaging systems. Considering the AE results in the examined energies, as well as the spectral compatibility with various photodetectors, a CaF2:Eu single crystal could be considered for radiographic applications, including the detection of charged particles and soft gamma rays.

Highlights

The use of single crystals as radiation converters is very common in imaging or counting applications, especially when coupled with optical sensors such as photomultipliers, which are frequently employed in radiation detectors [1,2]
Mm3 CaF2 :Eu crystal had increased absolute luminescence efficiency (AE) compared to both lutetium oxyorthosilicate and bismuth oxyorthosilicate (LSO) and bismuth germinate oxide (BGO), across the examined kVp range [28]
The absolute luminescence efficiency and the spectral matching of a CaF2 :Eu crystal were investigated in conditions usually met in general radiography

Summary

Introduction

The use of single crystals as radiation converters is very common in imaging or counting applications, especially when coupled with optical sensors such as photomultipliers, which are frequently employed in radiation detectors [1,2]. The state-of-the-art electronics that are used in today’s imaging systems require scintillators with exceptional properties, which are tailored for every application [1,17,18,19] This is a prerequisite for medical imaging, where the need for exceptional quality of the diagnostic images as well as the lowest possible radiation exposure of patients as directed by the ALARA principle (as low as reasonably achievable) is a priority [20]. Similar concerns arise in other fast applications such as CT, in which afterglow can cause blur in the final image [7]

Methods

Results

Conclusion