Radioluminescence Sensitization in Scintillators and Phosphors: Trap Engineering and Modeling

Moretti, Federico; Patton, Gaël; Belsky, A.; Fasoli, M.; Vedda, A.; Trevisani, Mattia; Bettinelli, Marco; Dujardin, Christophe

doi:10.1021/jp501717z

Cited by 54 publications

(47 citation statements)

References 25 publications

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“…In general, the shape of the hysteresis curve depends on several parameters. 17 Some of the parameters are related to the experimental conditions used to investigate the phenomenon, like temperature and dose rate. Others are strictly correlated with the nature of the competing traps and thus the material.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Role of Optical Fiber Drawing in Radioluminescence Hysteresis of Yb-Doped Silica

et al. 2015

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Point defects in the host lattice of a scintillator material can trap carriers, slowing down their migration or even preventing their transfer to luminescent centers. Such competition schemes between defects and luminescent centers may explain also the hysteresis effect, which consists of a progressive enhancement of scintillation efficiency with accumulated dose. We propose a comparison between the scintillation hysteresis effect of Yb-doped sol−gel silica glasses in bulk and fiber forms, and we correlate them with traps monitored by wavelength-resolved thermally stimulated luminescence in both materials. The results demonstrate that the fiberdrawing process is responsible for modifications of the defectiveness of the glass network, with a change of the local distribution of the traps surrounding the luminescent center. The consequence of such modifications is the removal, in the fiber samples, of the thermally stimulated luminescence peak ascribed to traps closer to Yb ions and unstable at room temperature. We highlight that suitable postdensification thermal treatments can significantly modify the concentration and spatial distribution of defects around a luminescent center and can therefore be used as a tool for the engineering of scintillating glasses.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Role of Optical Fiber Drawing in Radioluminescence Hysteresis of Yb-Doped Silica

et al. 2015

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“…Furthermore, the deep trapping defects that compete with the luminescent centers for charge-carrier capture could be permanently fi lled and made inactive by a pre-irradiation process. As a result of such a procedure, a signifi cant improvement in the stability of both the RL effi ciency and light yield was indeed obtained in several scintillator single crystals like BaAl 4 [34][35][36] For LuAG:Ce, a RL increase of about 30% was noticed after an X-irradiation at 50 Gy. [ 36 ] Such a process could possibly work also for LuAG:Ce,Mg ceramics and give rise to a further improvement of their performance.…”

Section: Full Paper Full Paper Full Papermentioning

confidence: 96%

Towards Bright and Fast Lu₃Al₅O₁₂:Ce,Mg Optical Ceramics Scintillators

Liu

Mareš

Feng

et al. 2016

Advanced Optical Materials

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needed. Within the last two decades, a number of excellent scintillators based on Ce 3+ and Pr 3+ -doped materials, together with truly novel nanoscintillators, nanocomposites, and phase-separated material systems, have been discovered and studied in depth. [1][2][3][4][5][6][7][8] This high R&D activity in the scintillator fi eld was triggered by the pressing needs of modern medical imaging and radiotherapy, of high-energy physics, homeland security, and environmental applications. Among them, Cedoped Lu 3 Al 5 O 12 (LuAG:Ce) aluminum garnets have attracted much attention because of their relatively high density of 6.73 g cm −3 , 5d -4f electric dipole allowed radiative transition of Ce 3+ with emission at around 500-550 nm, fast scintillation response of about 60 ns, and high theoretical light yield (LY) value of 60000 photons/MeV. [ 9,10 ] It was found that LuAG:Ce single crystal containing 0.55 at% Ce 3+ ions prepared by Bridgman technique is a highly competitive scintillator displaying a LY of about 26000 photons/MeV with a shaping time of 1.5 μs, close to that of Lu 2 SiO 5 :Ce (LSO:Ce). [ 11 ] Based on the understanding of defect chemistry, an effective bandgap engineering approach was successfully applied to the LuAG system. Multicomponent garnets, featuring a balanced admixture of Gd and Ga cations in the Lubased garnet structure, form a new family of materials with an amazingly high light yield up to 58000 photons/MeV, a value exceeding that of the best Lu 2-x Y x SiO 5 :Ce (LYSO:Ce) materials by about 40%. [12][13][14][15] Therefore, oxides based on garnet structure are presently considered as competitive candidates for advanced scintillation applications.However, the low segregation coeffi cient of Ce 3+ ions in the LuAG lattice is detrimental for the growth of homogeneously doped large LuAG:Ce single crystals, especially for high Ce 3+ concentrations (Ce 3+ > 0.2 at%). [ 16 ] It was also noticed that Lu Al antisite defects (AD) can severely deteriorate the scintillation characteristics of LuAG:Ce single crystals by acting as shallow traps, thus delaying the energy transport to the Ce 3+ emission centers. [ 17 ] Therefore, extensive research has recently been aimed at the preparation of ceramic analogues, which are characterized by lower preparation temperatures, more uniform doping, and lower cost. One point to consider is that during The choice of sintering agent appears critical to achieve both high optical transparency and scintillation performance. In this work, the optical investigations coupled with X-ray absorption near-edge spectroscopy evidence the benefi cial role of MgO sintering agent. Mg 2+ co-dopants in ceramics drive the partial conversion of Ce 3+ to Ce 4+ . The Ce 4+ center, however, does not impair the scintillation performance due to its capability to positively infl uence the scintillation process. The importance of simultaneous application of such co-doping and annealing treatment is also demonstrated. With 0.3 at% Mg, our ceramics display a light yield of ≈25000 photons/MeV wit...

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“…Indeed, as for many other scintillation materials, [21][22][23][24] the RL sensitivity of the Yb-doped silica fiber was observed to increase as a consequence of a prolonged exposition to ionizing radiation.…”

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confidence: 85%

“…[21][22][23][24] This competing process, being dependent on the concentration of empty traps with respect to that of the luminescent centers, becomes less relevant as traps are progressively populated during the irradiation, and it runs out once the competing traps are totally filled.…”

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confidence: 99%

Infrared luminescence for real time ionizing radiation detection

Veronese

Mattia

Fasoli

et al. 2014

Applied Physics Letters

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Radio-luminescence (RL) optical fiber sensors enable a remote, punctual, and real time detection of ionizing radiation. However, the employment of such systems for monitoring extended radiation fields with energies above the Cerenkov threshold is still challenging, since a spurious luminescence, namely, the “stem effect,” is also generated in the passive fiber portion exposed to radiation. Here, we present experimental measurements on Yb-doped silica optical fibers irradiated with photon fields of different energies and sizes. The results demonstrate that the RL of Yb3+, displaying a sharp emission line at about 975 nm, is free from any spectral superposition with the spurious luminescence. This aspect, in addition with the suitable linearity, reproducibility, and sensitivity properties of the Yb-doped fibers, paves the way to their use in applications where an efficient stem effect removal is required.

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Radioluminescence Sensitization in Scintillators and Phosphors: Trap Engineering and Modeling

Cited by 54 publications

References 25 publications

Role of Optical Fiber Drawing in Radioluminescence Hysteresis of Yb-Doped Silica

Role of Optical Fiber Drawing in Radioluminescence Hysteresis of Yb-Doped Silica

Towards Bright and Fast Lu₃Al₅O₁₂:Ce,Mg Optical Ceramics Scintillators

Infrared luminescence for real time ionizing radiation detection

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Radioluminescence Sensitization in Scintillators and Phosphors: Trap Engineering and Modeling

Cited by 54 publications

References 25 publications

Role of Optical Fiber Drawing in Radioluminescence Hysteresis of Yb-Doped Silica

Role of Optical Fiber Drawing in Radioluminescence Hysteresis of Yb-Doped Silica

Towards Bright and Fast Lu3Al5O12:Ce,Mg Optical Ceramics Scintillators

Infrared luminescence for real time ionizing radiation detection

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Towards Bright and Fast Lu₃Al₅O₁₂:Ce,Mg Optical Ceramics Scintillators