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Gadolinium Garnet transparent ceramics doped with Ce, ((Gd,Y,Ce)3(Ga,Al)5O12), for gamma-ray spectroscopy provide high density, high light yield, high energy resolution , high Z, mechanical robustness, and they are unreactive to air and water. Gadolinium garnet single crystals are costly to grow, due to their high melting points, and suffer from non-uniform light yield, due to Ce segregation. In contrast, transparent polycrystalline ceramic Garnets are never melted, and therefore are less costly to produce and provide the uniform light yield required to achieve high energy resolution with a scintillator. GYGAG(Ce) transparent ceramics offer energy resolution as good as R(662 keV) = 3.5%, in a pixelated detector utilizing Silicon photodiode array readout. We have developed a modular handheld detector based on pixelated GYGAG(Ce) on a photodiode array, that offers directional detection for point source detection as well as gamma spectroscopy. Individual modules can be assembled into detectors ranging from pocket-size to large panels, for a range of applications. Large GYGAG(Ce) transparent ceramics in the 2-5 in3 size range have been fabricated at LLNL. Instrumentation of these ceramics with Silicon photomultipliers (SiPMs) and super bi-alkali PMTs has been explored and energy resolution as good as R(662 keV) = 5% has been obtained. Further improvements with SiPM readout will leverage their high quantum efficiency in the 500-650 nm range where GYGAG(Ce) emits, and implement electronics that minimize the effect of SiPM dark current and capacitance on the pulse height spectra. This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and has been supported by the US Department of Homeland Security, Domestic Nuclear Detection Office, under competitively awarded IAA HSHQDC-12-X-00149 under Contract No. DE-AC03-76SF00098. LLNL-ABS-724480.

New transparent ceramic scintillators offer advantages for applications in gamma spectroscopy and X-ray imaging. For gamma spectroscopy, excellent light yield, material uniformity, light yield proportionality, mechanical and environmental ruggedness can be achieved in polycrystalline ceramic oxide garnets. We have fabricated 5 in3 Ce-doped Gd garnet transparent ceramics. GYGAG(Ce) garnet transparent ceramics offer $^{\mathbf {\rho \, =\, 5.8g/cm^{3},\,}}$, $z_{eff}=48$, principal decay of 2 O 3 structure structure. The 12” x 12” GLO imaging plates outperform scintillator glass for MeV radiography, due to higher light yield (55,000 Ph/MeV) and better stopping, while providing spatial resolution of >8 lp/mm for MeV X-rays.

Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of

We report on the development of two new mechanically rugged, high light yield transparent ceramic scintillators: (1) Ce-doped Gd-garnet for gamma spectroscopy, and (2) Eu-doped Gd-Lu-bixbyite for radiography. GYGAG(Ce) garnet transparent ceramics offer ρ = 5.8g/cm3, Zeff = 48, principal decay of 8 lp/mm.

Development of the Europium-doped Strontium Iodide scintillator, SrI2(Eu2+), has progressed significantly in recent years. SrI2(Eu2+) has excellent material properties for gamma ray spectroscopy: high light yield (

Breakthrough energy resolution, R(662keV) < 4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce). Transparent ceramic GYGAG(Ce), has a peak emission wavelength of 550 nm that is better matched to Silicon photodetectors than to standard PMTs. We are therefore developing a spectrometer based on pixelated GYGAG(Ce) on a Silicon photodiode array that can provide R(662 keV) = 3.6%. In comparison, with large 1-2 in3 size GYGAG(Ce) ceramics we obtain R(662 keV) = 4.6% with PMT readout. We find that ceramic GYGAG(Ce) of a given stoichiometric chemical composition can exhibit very different scintillation properties, depending on sintering conditions and post-anneal treatments. Among the characteristics of transparent ceramic garnet scintillators that can be controlled by fabrication conditions are: scintillation decay components and their amplitudes, intensity and duration of afterglow, thermoluminescence glow curve peak positions and amplitudes, integrated light yield, light yield non-proportionality - as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI), and energy resolution for gamma spectroscopy. Garnet samples exhibiting a significant fraction of Cerium dopant in the tetravalent valence also exhibit: faster overall scintillation decay, very low afterglow, high light yield, but poor light yield proportionality and degraded energy resolution.

Recently discovered scintillators for gamma ray spectroscopy, single crystal SrI{sub 2}(Eu), GYGAG(Ce) transparent ceramic and Bismuth-loaded plastics, offer resolution and fabrication advantages compared to commercial scintillators, such as NaI(Tl) and standard PVT plastic. Energy resolution at 662 keV of 2.7% is obtained with SrI{sub 2}(Eu), while 4.5% is obtained with GYGAG(Ce). A new transparent ceramic scintillator for radiographic imaging systems, GLO(Eu) offers high light yield of 70,000 Photons/MeV, high stopping, and low radiation damage. Implementation of single crystal SrI{sub 2}(Eu), Gd-based transparent ceramics, and Bi-loaded plastic scintillators can advance the state-of-the art in ionizing radiation detection systems.

We are developing new scintillator materials that offer potential for high resolution gamma ray spectroscopy at low cost. Single crystal SrI 2 (Eu) offers ∼3% resolution at 662 keV, in sizes of ∼1 in3. We have developed ceramics processing technology allowing us to achieve cubic inch scale transparent ceramic scintillators offering gamma spectroscopy performance superior to NaI(Tl). Our bismuth-loaded plastic scintillator demonstrates energy resolution of ∼8% at 662 keV, for samples of ∼0.5 cm3.

Transparent ceramics combine the scintillation performance of single crystals with the ruggedness and processability of glass. We have developed a versatile, scaleable fabrication method, wherein nanoparticle feedstock is consolidated at temperatures well below melting to form inch-scale phase-pure transparent ceramics with optical scatter of α

Ceramic and single crystal Lutetium Aluminum Garnet scintillators exhibit energy resolution with bialkali photomultiplier tube detection as good as 8.6% at 662 keV. Ceramic fabrication allows production of garnets that cannot easily be grown as single crystals, such as Gadolinium Aluminum Garnet and Terbium Aluminum Garnet. Measured scintillation light yields of Cerium-doped ceramic garnets indicate prospects for high energy resolution.