Industrial Biotechnology Innovation Centre

Silicon Photomultipliers (SiPM) have shown great promise as a suitable replacement for conventional vacuum based Photomultiplier Tubes (PMT). Progress in recent years has been vast with SiPM sensors pushing the boundaries in energy and timing resolution as well as photon detection efficiency and active surface area. In this study we report the energy resolution and linearity of two novel scintillator crystals, Cerium doped Gd3Al2Ga3O12 (Ce:GAGG) and Praseodymium doped Lu3Al5O12 (Pr:LuAG), readout by three different types of $3\times 3~\mathrm {mm}^{2}$ silicon photomultiplier sensors produced by SensL (MicroFM, MicroFB, MicroFC). Such a scintillator-SiPM architecture has applications in pre-clinical and clinical medical imaging modalities such as Positron Emission Tomography (PET). N-on-P (M series), P-on-N (B series) and low-noise P-on-N (C series) versions of the SiPM sensor platform have been coupled to the crystals and the response characterized over a range of gamma energies and detector bias values. A saturation-corrected energy resolution of 11.7% was achieved for a MicroFM device coupled to a $3\times 3\times 30~\mathrm {mm}^{3}$ Ce:GAGG crystal at 20°C. An energy resolution of 16.1% was obtained for a MicroFB device optically coupled to to a $3\times 3\times 30~\mathrm {mm}^{3}$ Pr:LuAG crystal at 20°C.

Scintillators are a critical component of sensor systems for the detection of ionizing radiation. Such systems have a diverse portfolio of applications from medical imaging, well logging in oil exploration, and detection systems for the prevention of the illicit movement of nuclear materials. The rare earth element cerium is an ideal dopant for a variety of host scintillating materials due to the fast $5{{\rm d}_1} \rightarrow {4} {\rm f}$ radiative transition of ${{\rm Ce}^{3 + }}$ . Cerium-doped gadolinium aluminium gallium garnet (Ce:GAGG) is a relatively new single crystal scintillator with several interesting properties. These include high light yield, an emission peak well-matched to silicon sensors, and low intrinsic energy resolution. Moreover, the material has high density and is nonhygroscopic. In this paper, we review the properties of cerium-doped GAGG and report energy-resolution (ER) measurements over the temperature range $- {\hbox {10}}^\circ\text{C}$ to $+ {\hbox {50}}^\circ \text{C}$ for ${\hbox \times {\hbox \times {\hbox {30}} \hbox{mm}^{3}$ Ce:GAGG crystals optically coupled to a silicon photomultipler (SiPM) sensor with a ${\hbox {3}} \hbox{mm} \times {\hbox {3}} \hbox{mm}$ active area. In addition, the linearity of the scintillator-SiPM response as a function of gamma energy is reported.