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III-nitrides have fomented a revolution in the lighting industry and are poised to make a huge impact in the field of power electronics. In the III-nitride family, the crystal growth and use of hexagonal BN (h-BN) as an ultrawide bandgap (UWBG) semiconductor are much less developed. Bulk crystals of h-BN produced by the high-temperature/high-pressure and the metal flux solution methods possess very high crystalline and optical qualities but are impractical to serve as substrates or for device implementation as their sizes are typically in millimeters. The development of crystal growth technologies for producing thick epitaxial films (or quasi-bulk or semi-bulk crystals) in large wafer sizes with high crystalline quality is a prerequisite for utilizing h-BN as an UWBG electronic material. Compared to traditional III-nitrides, BN has another unique application as solid-state neutron detectors, which however, also require the development of quasi-bulk crystals to provide high detection efficiencies because the theoretical efficiency (ηi) relates to the detector thickness (d) by η i = 1 − e − d λ , where λ denotes the thermal neutron absorption length which is 47 μm (237 μm) for 10B-enriched (natural) h-BN. We provide an overview and recent progress toward the development of h-BN quasi-bulk crystals via hydride vapor phase epitaxy (HVPE) growth and the attainment of thermal neutron detectors based on 100 μm thick 10B-enriched h-BN with a record efficiency of 60%. The thermal neutron detection efficiency was shown to enhance at elevated temperatures. Benchmarking the crystalline and optical qualities of h-BN quasi-bulk crystals with the state-of-the-art mm-sized bulk crystal flakes and 0.5 μm thick epitaxial films identified that reducing the density of native defects such as vacancies remains the most critical task for h-BN quasi-bulk crystal growth by HVPE. [ABSTRACT FROM AUTHOR]

With the rapid development of silicon-based light detectors with high detection efficiency and long-wavelength sensitivity, the development of near-infrared scintillation crystals has become a hotspot. Especially, the Sm2+ doped europium-based halide crystals exhibit excellent near-infrared luminescence properties. In this paper, Cs4 EuI6: Sm near-infrared scintillation crystals with a size of cm-level were successfully prepared by Bridgman method. The composition and structure were discussed by XRD, XPS and ICP-OES methods, indicating that the Sm2+ was introduced and has no obvious effect on the crystal structure of the matrix. Under ultraviolet and X-ray excitation, the crystal has two luminescence centers (Eu2+ and Sm2+), and the emission peaks are located at 450 and 840 nm, respectively, corresponding to the 5d→4f luminescence of Eu2+ and Sm2+. The decay time of Eu2+ and Sm2+ is at the level of microsecond under ultraviolet excitation. The results show that the emission wavelength gradually varies from blue to near infrared as Sm2+ doping concentration increased. The effects of Sm2+ concentration on the luminescence properties, Eu2+ -Sm2+ energy transfer and decay time of the crystals were also studied, which means that the luminescence properties can be tuned by adjusting the Sm2+ doping concentration. [ABSTRACT FROM AUTHOR]

A single crystal of Zn2Te3O8 (ZTO) was grown using the conventional Czochralski technique. TGA analysis showed that the melting point of ZTO is 681 °C, while it exhibits a structural phase transition at 621 °C. The powder X-ray diffraction analysis of ZTO confirmed that it possesses a single crystalline monoclinic structure with the C2/c space group. An indirect band gap of 3.75 eV was estimated for the ZTO crystal based on its absorption spectrum. The X-ray-induced luminescence of the grown crystal comprised a broad band peaking at 565 nm, which can be tentatively assigned to the self-trapped exciton emission from the (Te3O8)4− molecular complexes. The photoluminescence measured under 280 nm excitation showed a broad band luminescence peaking at about 600 nm, and its intensity was significantly enhanced upon cooling the crystal from 300 K to 10 K. The photoluminescence decay time under 280 nm excitation was shown to have two exponential components in the range from 10 K to 175 K, which became a single exponential upon further heating the crystal. Low scintillation light was observed at room temperature both under α- and β-particle excitations from 241Am and 90Sr sources, respectively. The scintillation light yield measured under β-particle excitation from the 90Sr source was enhanced by about five orders of magnitude at 10 K in comparison to that at 300 K. The scintillation light yield measured at 10 K under the same experimental conditions for ZTO in comparison with the well-known cryogenic scintillator Li2MoO4 (LMO) was shown to have four times higher scintillation light. A single-crystal ingot of ZTO was obtained for the first time; however, it had several cracks due to its phase transition. Notably, scintillation at low temperatures for a Te-based crystal was observed for the first time. These preliminary findings are very promising and show that ZTO will be a good candidate for cryogenic phonon scintillation detectors for the 0νββ decay search of 130Te. [ABSTRACT FROM AUTHOR]

Scintillators are used not only as single crystals in radiation detection systems but also as arrays, columns, and fibers. In this study, a novel optical-guiding crystal scintillator (OCS) was fabricated using an Eu:SrI 2 crystal as the core and borosilicate glass as the cladding. The OCS has an elongated shape and can be flexibly processed like an optical fiber. Furthermore, because inorganic scintillator crystals are used as the core, the OCS has high sensitivity to high-energy radiation, such as γ- and X-ray radiation, unlike plastic scintillators. In this study, by observing the cross section of the fabricated OCS, identifying the crystal structure, and investigating the radioluminescence spectrum under X-ray irradiation, OCS fabrication in accordance with the OCS design specifications was confirmed, and the SrI 2 crystal structure and Eu2+ 5d–4f luminescence were maintained. The γ-ray responses, such as light yield and decay time, were also investigated. [ABSTRACT FROM AUTHOR]

In this paper, Φ25 mm lanthanum bromide scintillation crystals with 5%Ce3+ and different Sr2+ doping concentrations (0.1%, 0.3%, 0.5% in molar ratio) were successfully grown by spontaneous nucleation vertical Bridgman method. X-ray excited emission spectra, transmission spectra and pulse height spectra of these crystals were measured. Results show that, the emission spectra waveform of LaBr3:Ce crystals with different Sr2+ doping concentrations is basically consistent under X-ray excitation, and the emission peak shows a significant red shift compared with that of sample without Sr2+ doping. With the increase of Sr2+ doping concentration, the emission peak of LaBr3:Ce,Sr crystal shows a slight red shift. There is no obvious absorption peak range from 350 to 800 nm of LaBr3:Ce,Sr crystals with different Sr2+ doping concentrations. Compared with LaBr3:Ce crystals, transmittance of 0.3% and 0.5% Sr2+ doped LaBr3:Ce crystals decrease. In addition, with the increase of Sr2+ doping concentration, the energy resolution of the crystal increases correspondingly. LaBr3:Ce,0.5% Sr crystal has the highest energy resolution of 2. 99%@662 keV. The energy resolution of the encapsulated LaBr3:Ce,0.5%Sr crystal with size of Φ25 mm x 25 mm is 2.93%@662 keV. [ABSTRACT FROM AUTHOR]

Gadolinium scandium aluminum garnet scintillator crystals (GSAG:Ce) with Ca2+, Mg2+, and Li+ co‐dopants are grown by the Bridgman method under reducing atmosphere. Crystals are irradiated with a 60Co gamma‐ray source to 10 kGy and 50 kGy doses for evaluation of the radiation hardness. A wide absorption band peaking at around 620 nm is observed in all as‐grown uncodoped GSAG:Ce crystals. Air annealing at high temperatures and introduction of codopants result in elimination of this absorption band and improvement of transmittance in the visible range. The nature of the color center at ≈620 nm is discussed. GSAG:Ce crystals codoped with Li+ and Mg2+:Li+ combine both high transmission and least radiation damage. [ABSTRACT FROM AUTHOR]

Halide scintillation crystals with neutron-gamma dual detection capabilities show broad application prospects in the field of radiation detection. High optical quality NaI∶Tl and NaI∶Tl,Li scintillation crystals were grown by Bridgman method in this paper. The photoluminescence excitation (PLE) and emission (PL), time-resolved photoluminescence, X-ray excited radioluminescence (XEL), γ-ray detection performance and neutron-gamma discrimination performance of NaI∶Tl co-doped with different Li concentrations were systematically studied. Under the excitation of X-ray, NaI∶Tl and NaI∶Tl,Li crystals show emission peaking at 345 and 410 nm respectively, which are related to sp-s² transitions of Tl+ ion. As the increase of Li co-doping concentration, the light yield of the crystal decreases from 41 000 photons/MeV to 23 000 photons/ MeV, while the energy resolution at 662 keV deteriorates from 7. 0% to 9. 6%. Among the tested samples, the NaI∶Tl crystal co-doped with 1% Li has the best neutron-gamma pulse shape discrimination (PSD) performance, and the neutron-gamma PSD figure-of-merits (FoM) reaches 4.56. [ABSTRACT FROM AUTHOR]

This study aims to determine the optimum composition of the CeBr1−xIx compound to achieve the maximum light output. It is based on calculations of the band energy structure of crystals, specifically taking into account the characteristics of the mutual location of local and band 5d states of the Ce3+ ions. The band energy structures for CeBr2I and CeBrI2 crystals were calculated using the projector augmented wave method. The valence band was found to be formed by the hybridized states of 4p Br and 5p I. The 4f states of Ce3+ are located in the energy forbidden band gap. The conduction band is formed by the localized 5d1 states, which are created by the interaction between the 5d states of Ce3+ and the 4f0 hole of the cerium ion. The higher-lying delocalized 5d2 states of Ce3+ correspond to the energy levels of the 5d states of Ce3+ in the field of the halide Cl0 (Br0) hole. The relative location of 5d1 and 5d2 bands determines the intensity of 5d–4f luminescence. The bottom of the conduction band is formed by localized 5d1 states in the CeBr2I crystal. The local character of the bottom of the conduction band in the CeBr2I crystal favors the formation of self-trapped Frenkel excitons. Transitions between the 5d1 and 4f states are responsible for 5d–4f exciton luminescence. In the CeBrI2 crystal, the conduction band is formed by mixing the localized 5d1 and delocalized 5d2 states, which leads to quenching the 5d–4f luminescence and a decrease in the light output despite the decrease in the forbidden band gap. CsBr2I is the optimum composition of the system to achieve the maximum light output. [ABSTRACT FROM AUTHOR]

The 40 mm x 40 mm x 350 mm BaF2:5%Y (mole fraction) crystals were grown by vertical Bridgman method. The doping content, scintillation properties, optical properties and irradiation damage of crystal samples were studied. The Y3+ doping concentration (mole fraction) is 5. 1% ± 0. 9% within the range from 0 to 300 mm from seed end. The average light output of crystal sample is 2 100 ph / MeV, and the optimal energy resolution at 662 keV is 10. 1%. After 60Co source was used to irradiate the sample with an accumulated dose of 1 Mrad, the transmittance of the sample at 220 nm wavelength decreases from 87. 3% before irradiation to 83. 5%, the transmittance at 300 nm wavelength decreases from 91. 8% to 89. 9%. The anti-irradiation performance of BaF2:Y crystal is worse than that of BaF2 crystal. After the accumulative dose irradiation, the absorption of BaF2:Y crystal to 300 nm light is significantly enhanced. [ABSTRACT FROM AUTHOR]

It is well known that scintillator performance, especially its energy resolution, is highly dependent on its homogeneity which is determined through its growth process. Therefore, examination and quality control of synthesized scintillators is an important step towards their improvement. Ionoluminescence (IL) microscopy is a highly sensitive and non-destructive technique which can reveal the texture, chemical composition and distribution of trace elements in the inhomogeneous specimens. In this research work, IL microscopy technique is employed for the first time to provide images of two synthesized CsI(Na) crystals. The results show that IL microscopy is not only capable of determining the distribution of the total luminescence emitted from each point, but can also determine it for individual luminescence bands, which represents special luminescence centers in the sample. Therefore, IL microscopy is introduced as a high potential technique for effective characterization of scintillators. [ABSTRACT FROM AUTHOR]

The characteristics of a Silicon Photo Multiplier (SiPM)-based scintillation detector system were studied. The influence of the bias voltage and the number of SiPMs on the energy resolution was identified. The single SiPM energy spectra in the multi-SiPM system showed their dependency on the position of the 60Co radiation source. The application of geometric mean on the multi-SiPM system was also considered to bypass single channel calibrations. Preliminary results on the performances of developing scintillation detectors with a CsI(Tl) crystal or a plastic scintillator are demonstrated. The capability of charged particle measurement for CsI(Tl) crystal and sub-nanosecond timing resolution of plastic scintillator were identified. [ABSTRACT FROM AUTHOR]

A large NaI(Tl) crystal with a volume of 4 L was grown by Bridgman method. The crystal was tested by X-ray powder diffraction and UV-Visible near-infrared transmission spectroscopy. The results show that the crystal has a single phase and the transmittance is higher than 75% at 600 ~ 1 600 nm. The results of inductively coupled plasma emission spectroscopy show that the concentration of Tl ions in the crystal gradually increases from head to tail. After forging, cutting, grinding, polishing and packaging, NaI(Tl) crystal blank was made into square crystal with 100 mm x 50 mm x 400 mm. The scintillation property measurement shows that the average energy resolution of crystal is 7.9% under the excitation of 137Cs radioactive source, and the relative light output and energy resolution at different locations are different. [ABSTRACT FROM AUTHOR]

Undoped, 0.5, 1.0, and 2.0% Nd-doped Bi4Si3O12 (BSO) crystals were synthesized by the floating zone method. Regarding photoluminescence (PL) properties, all samples had emission peaks due to the 6p–6s transitions of Bi3+ ions. In addition, the Nd-doped samples had emission peaks due to the 4f–4f transitions of Nd3+ ions as well. The PL quantum yield of the 0.5, 1.0, and 2.0% Nd-doped samples in the near-infrared range were 67.9, 73.0, and 56.6%, respectively. Regarding X-ray-induced scintillation properties, all samples showed emission properties similar to PL. Afterglow levels at 20 ms after X-ray irradiation of the undoped, 0.5, 1.0, and 2.0% Nd-doped samples were 192.3, 205.9, 228.2, and 315.4 ppm, respectively. Dose rate response functions had good linearity from 0.006 to 60 Gy/h for the 1.0% Nd-doped BSO sample and from 0.03 to 60 Gy/h for the other samples. [ABSTRACT FROM AUTHOR]

Single-crystalline films (SCFs) of the LuAG: Ce garnet grown using the liquid-phase epitaxy method onto YAG single-crystal (SC) substrates were investigated for possible applications as composite thermoluminescent (TL) detectors. Such detectors may help to register the different components of ionizing radiation fields with various penetration depths, e.g., heavy charged particles and gamma or beta rays. It was found that the TL signal of LuAG: Ce SCF sufficiently differs from that of the YAG substrate concerning both the temperature and wavelength of emissions. Furthermore, even by analyzing TL glow curves, it was possible to distinguish the difference between weakly and deeply penetrating types of radiation. Within a test involving the exposure of detectors with the mixed alpha/beta radiations, the doses of both components were determined with an accuracy of a few percent. [ABSTRACT FROM AUTHOR]

We present here a characterization of the low background NaI(Tl) crystal NaI-33 based on a period of almost one year of data taking (891 kg × days exposure) in a detector configuration with no use of organic scintillator veto. This remarkably radio-pure crystal already showed a low background in the SABRE Proof-of-Principle (PoP) detector, in the low energy region of interest (1–6 keV) for the search of dark matter interaction via the annual modulation signature. As the vetoable background components, such as 40 K, are here sub-dominant, we reassembled the PoP setup with a fully passive shielding. We upgraded the selection of events based on a Boosted Decision Tree algorithm that rejects most of the PMT-induced noise while retaining scintillation signals with > 90% efficiency in 1–6 keV. We find an average background of 1.39 ± 0.02 counts/day/kg/keV in the region of interest and a spectrum consistent with data previously acquired in the PoP setup, where the external veto background suppression was in place. Our background model indicates that the dominant background component is due to decays of 210 Pb, only partly residing in the crystal itself. The other location of 210 Pb is the reflector foil that wraps the crystal. We now proceed to design the experimental setup for the physics phase of the SABRE North detector, based on an array of similar crystals, using a low radioactivity PTFE reflector and further improving the passive shielding strategy, in compliance with the new safety and environmental requirements of Laboratori Nazionali del Gran Sasso. [ABSTRACT FROM AUTHOR]

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements [ABSTRACT FROM AUTHOR]

Ce:LuAG crystal is an excellent scintillation material, but cracking and inclusion defects often occur when Ce:LuAG is grown by Czochralski method. In this paper, the effects of temperature gradient, pulling speed, rotation speed and thermal strain on crystal defects were analyzed by combining theory with practice, and the solution was put forward. The suitable technological parameters for growing Ce:LuAG crystal with high quality are given: the temperature gradient above the melt is about 5 ° / mm, the shoulder angle is 30° ~ 60°, the pulling speed is 1. 0 ~ 1. 5 mm/ h, and the crystal rotation speed is 15 ~25 r/ min. Finally, good quality of Ce:LuAG single crystal with a diameter of 30 mm and an equal diameter length of 50 mm is successfully grown, and the crystal core area is small. [ABSTRACT FROM AUTHOR]

GdTaO4 and LuTaO4 are heavy scintillators with fast decay fluorescence. The photoluminsecence spectra of M phase Nd:GdTaO4 and M′ phase Nd:LuTaO4 excited by a laser diode (LD) of 808 nm were fitted with the full-profile fitting method, and the transition intensity parameters Akt, p were determined. Under the excitation of 808 nm LD laser, the population ratio between the upper and low crystal field energy levels of 4 F3/2 for Nd3+ in GdTaO4 is near to 1, but in LuTaO4 is 1.30 and 1.41, which indicates that the relaxation rate between two crystal field energy levels is nearly equal to the excitation rate of LD. The Judd-Ofelt transition intensity parameters Ωt were calculated with Akt, p, and the transition probabilities from 2 P3/2 of Nd3+ in GdTaO4 and LuTaO4 were computed, which indicates that the fast decay fluorescence of several hundred nanoseconds of Nd3+ in GdTaO4 and LuTaO4 is caused by the high nonradiative transition. [ABSTRACT FROM AUTHOR]

This paper presents the gamma-ray detection performance of the newly developed MAPD-3NM-II type SiPM sensor array (4 × 4) with LaBr 3 (Ce) scintillator. The gamma-ray spectra of various sources have been measured in the energy range from 26 keV up to 1332 keV. The newly developed array based on MAPD-3NM-II sensors proved ∼ 22% enhancement in energy resolution in comparison to the former MAPD-3NM-I based array. The energy resolution of 662 keV gamma-rays measured by MAPD-3NM-II was 3.3% while clearly surpassing 4.25% resolution of MAPD-3NM-I predecessor. The enhancement is related to the high PDE of the new MAPD-3NM-II. Obtained results show that the new MAPD-3NM-II demonstrated good energy resolution and linearity in the studied energy region. The energy resolution of the new detector developed based on MAPD-3NM-II was better than all previous products of MAPD. [ABSTRACT FROM AUTHOR]

NaI(Tl) scintillators can detect thermal neutrons with surprising efficiency, even in the presence of ambient gamma radiation. This is due to a peculiarity of the 128I level scheme. Deexcitation cascades following neutron captures in 127I, a main constituent of NaI with quite large neutron capture cross section, unexpectedly often involve the 167.4 keV state of 128I with 175 ns half-life, which feeds another isomeric level at 137.9 keV having a half-life of 845 ns. The 29.5 keV transition between both levels, as well as the subsequent deexcitation sequence to ground state comprising 137.9 keV sum energy, are almost certainly absorbed in the crystal. Signals including three scintillation pulses within few microseconds, the first one caused by a prompt part of the cascade, the second and third one disclosing 30 and 138 keV energy depositions and characteristic delays, are clearly related to such neutron captures. Double-pulse sequences comprising only the primary pulse and a delayed 138 keV signal are also distinctive but more prone to load-dependent background by random pulse pileups. This article demonstrates neutron detection with a Ø2” $\times2$ ” NaI(Tl) scintillation detector by finding and analyzing such double- and triple-pulse sequences in digitized detector signals. It quantifies effect and background rates as a function of the detector load ranging up to 30 kcps. Complementary measurements with a 6Li codoped Ø2” $\times2$ ” NaI(Tl) (NaIL) scintillator allow relating the neutron detection yield by delayed-coincidence counting to the 6Li capture rate in the same crystal and thus to evaluate prospects and limits of this technique. [ABSTRACT FROM AUTHOR]

25. 4 mm diameter crystals of CeB- and three analogues doped with 0.1%, 0. 2% and 0. 5% of Sr2 + in molar ratio were grown by the vertical Bridgman method. The grown crystals were processed into 25. 4 mm diameter wafer with a thickness of 10 mm and characterized by fluorescence spectra excited by UV light and X-ray as well as multi-channel analysis with 137 Cs source. Results show that the emission bands of the crystals under X-ray excitation are slightly red-shifted by Sr2 + doping, and with the increase of Sr2 + doping content, the energy resolution of the crystals are successively improved, while the light yield are gradually reduced. The CeB- crystal doped with 0. 5% Sr2 + exhibits the best energy resolution of 3. 83% @ 662 keV. However, high Sr2 + doping also causes difficulty in crystal growth. A doping content of 0. 2% is considered appropriate with regards to both scintillation property and crystal growth availability. An encapsulated CeBr3: 0. 2% Sr crystal with dimension of ©25.4 mm X25.4 mm is obtained and the energy resolution is 3. 92% @662 keV. [ABSTRACT FROM AUTHOR]

Background: Significant interest has been recently shown for using monolithic scintillation crystals in molecular imaging systems, such as positron emission tomography (PET) scanners. Monolithic‐based PET scanners result in a lower cost and higher sensitivity, in contrast to systems based on the more conventional pixellated configuration. The monolithic design allows one to retrieve depth‐of‐interaction information of the impinging 511 keV photons without the need for additional hardware materials or complex positioning algorithms. However, the so‐called edge‐effect inherent to monolithic‐based approaches worsens the detector performance toward the crystal borders due to the truncation of the light distribution, thus decreasing positioning accuracy. Purpose: The main goal of this work is to experimentally demonstrate the detector performance improvement when machine‐learning artificial neural‐network (NN) techniques are applied for positioning estimation in multiple monolithic scintillators optically coupled side‐by‐side. Methods: In this work, we show the performance evaluation of two LYSO crystals of 33 × 25.4 × 10 mm3 optically coupled by means of a high refractive index adhesive compound (Meltmount, refractive index n = 1.70). A 12 × 12 silicon photomultiplier array has been used as photosensor. For comparison, the same detector configuration was tested for two additional coupling cases: (1) optical grease (n = 1.46) in between crystals, and (2) isolated crystals using black paint with an air gap at the interface (named standard configuration). Regarding 2D photon positioning (XY plane), we have tested two different methods: (1) a machine‐learning artificial NN algorithm and (2) a squared‐charge (SC) centroid technique. Results: At the interface region of the detector, the SC method achieved spatial resolutions of 1.7 ± 0.3, 2.4 ± 0.3, and 2.6 ± 0.4 mm full‐width at half‐maximum (FWHM) for the Meltmount, grease, and standard configurations, respectively. These values improve to 1.0 ± 0.2, 1.2 ± 0.2, and 1.2 ± 0.3 mm FWHM when the NN algorithm was employed. Regarding energy performance, resolutions of 18 ± 2%, 20 ± 2%, and 23 ± 3% were obtained at the interface region of the detector for Meltmount, grease, and standard configurations, respectively. Conclusions: The results suggest that optically coupling together scintillators with a high refractive index adhesive, in combination with an NN algorithm, reduces edge‐effects and makes it possible to build scanners with almost no gaps in between detectors. [ABSTRACT FROM AUTHOR]

Correlations between the optical absorption spectra and integral thermal glow curves (300–600 K) of the Lu2SiO5:Ce scintillator crystals irradiated by 60Co gamma quanta with energies of 1.17 and 1.33 MeV at a dose rate of 1.1 Gy/s in the dose range of 70–5 × 107 Gy at a temperature of 310 K and their gamma luminescence have been investigated. The intrinsic defects before irradiation, including the neutral VO5 centers with an absorption band of 193 nm, ≡Si–VO5 (213 nm), Lu1–F+–Si (238 nm), Ce3+/Ce4+ (263 nm), as well as the Ce3+/F (295 nm) centers are generated during the technological process. Irradiation with doses of up to 5 × 104 Gy reduces the concentration of the VO5 centers, but does not affect the other centers. However, at doses of more than 5 × 104 Gy, the concentration of all the other defects in the LSO:Ce structure increases. The recovery of an optical absorption band of 193 nm and a decrease in the intensity of the thermal glow peak at 335 K with increasing time (1, 3, and 10 h) of exposure at 305 K, as well as the correlated growth of the optical absorption at 238 nm and the thermal glow peak at 540 K after irradiation with doses from 70 to 2.3 × 106 Gy are related to the release of electrons from these color centers and radiative recombination at the Ce1 centers. A decrease in the Ce3+ gamma luminescence yield in bands of 400 and 420 nm at doses of more than 105 Gy is possibly due to an increase in the concentration of the ≡Si–VO4, Lu1–F+–Si, and Ce3+/F centers competing with the Ce1 centers in trapping electrons. In this way, the upper limit of stability of the Lu2SiO5:Ce gamma scintillator (105 Gy) has been determined. [ABSTRACT FROM AUTHOR]

There is a global trend to increase the light yield of CsI scintillators used in neutrino and dark matter detection by operating undoped crystals at cryogenic temperatures. However, high light yield alone is not sufficient to guarantee a low-energy threshold. The response of undoped crystals to nuclear recoils at cryogenic temperatures is equally important. A liquid nitrogen-based cryostat was developed to measure the nuclear quenching factor of a small undoped CsI crystal using monoenergetic neutron beams at the Triangle Universities Nuclear Laboratory (TUNL). To minimize neutron scattering, high-Z materials were reduced around the crystal. The structure and performance of the cryostat are described in detail. Using this cryostat, a system light yield of 33. 4 ± 2. 0 photoelectrons per keV electron-equivalent (PE/keV ee) was observed at 5.9 keV ee , enabling the measurement of nuclear quenching factors at very low energies. The results of the quenching factor measurement will be reported in a subsequent paper. Non-negligible negative overshoot was observed in the tails of the observed light pulses. The origin of this issue and the correction procedure are described in detail. This information may be useful for others who encounter similar technical challenges. [ABSTRACT FROM AUTHOR]

The photoluminescence and scintillation properties of n-bromophenethylammonium lead chloride ((n-BrPEA) 2 PbCl 4) (n = 4, 3, and 2) and phenethylammonium lead chloride ((PEA) 2 PbCl 4) have been investigated. All the samples showed broad emission peaks at 400–700 nm upon excitation by UV light or X-ray. The decay time constants of 8–28 ns were obtained which originated from the recombination of self-trapped exciton (STE) within inorganic layers. The afterglow levels at 20 ms after 2 ms of X-ray irradiation of (4-BrPEA) 2 PbCl 4 and (3-BrPEA) 2 PbCl 4 (76 and 55 ppm) were better than (PEA) 2 PbCl 4 (379 ppm). The light yield of (4-BrPEA) 2 PbCl 4 (3100 photons/5.5 MeV-α) was higher than (PEA) 2 PbCl 4 (1400 photons/5.5 MeV-α). • (BrC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 crystals were grown by the slow cooling method. • All the crystals showed the luminescence due to the recombination of the self-trapped excitons confined in inorganic layers. • The (4-BrC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 crystal showed the highest QY in the present crystals. • The light yields of the (4-BrC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 crystals surpassed that of the unsubstituted crystal. [ABSTRACT FROM AUTHOR]

(n-ClC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 ((n-ClPEA) 2 PbCl 4) (n = 2, 3, and 4) and (n-C 6 H 5 C 2 H 4 NH 3) 2 PbCl 4 ((PEA) 2 PbCl 4) crystals were synthesized by the slow-cooling method, and the photoluminescence (PL) and scintillation properties were evaluated. All the samples showed self-trapped excitons luminescence at 400–700 nm. The PL quantum yields of the (n-ClPEA) 2 PbCl 4 (n = 2, 3, and 4) and (PEA) 2 PbCl 4 crystals were 2.2, 0.9, 11.2, and 2.2 %, respectively. In the pulse-height spectra of 241Am α-rays (5.5 MeV), full energy absorption peaks were observed, and the light yields of (n-ClPEA) 2 PbCl 4 (n = 2, 3, and 4) and (PEA) 2 PbCl 4 crystals were respectively calculated to be 530, 490, 2,800, and 1,400 photons/5.5 MeV-α with typical errors of ± 10 %. [ABSTRACT FROM AUTHOR]

In recent years, a number of new scintillator materials with improved energy resolution for gamma-ray detectors have become commercially available for use in terrestrial-based homeland security applications, and some are being incorporated into instrumentation for space. Unlike terrestrial applications, the harsh environment of space—in particular, energetic trapped particles, cosmic rays, and neutrons—often activates these materials, and any improvement in sensitivity as a result of improved energy resolution could be offset by the additional background due to activation. The purpose of this work was to measure potential backgrounds due to trapped and cosmic-ray proton-induced activation in the new materials: SrI2:Eu (SrI), 7Li-enriched Cs2LiYCl6:Ce (CLYC-7), Cs2LiLaBr6:Ce (CLLB), Cs2LiLa(Br,Cl)6:Ce (CLLBC), Tl2LiYCl6:Ce (TLYC), and Gd3(Al,Ga)5O12:Ce (GAGG). Using a large-diameter 64-MeV proton beam, detectors were irradiated with a total dose of 100 rad (Si), roughly equivalent to the annual dose in a typical low earth orbit. Measurements were made with a single 100% relative efficiency high-purity germanium (HPGe) (0.05–3 MeV) and the irradiated detector. Two multichannel analyzers (MCAs) operating in the event mode were used to collect the data. Time-tagged events were processed into various spectral integration times for analysis, and characteristic gamma-ray energies and decay times were used to identify activation products. Most of the identified activation products were the result of (p, xn) reactions, with a few exceptions. This work identifies the primary radioisotopes generated by energetic proton activation in six different scintillator materials. [ABSTRACT FROM AUTHOR]

Ce0.03Gd2.97Ga2Al3O12 (Ce:GGAG) single crystals were successfully grown by the traveling solvent floating zone method (TSFZ). A series of compositions, where the mole ratio is Gd2O3 : Al2O3 = 25 : 75, 27 : 73, 29 : 71, were investigated as solvents. The 25 mol% Gd2O3-75 mol% Al2O3 solvent component was found to be the most effective in stabilizing the molten zone to obtain a crystal rod with uniform diameter. The crystal cracks were relieved clearly due to the improved molten zone stabilization during the crystal growth process. XRD patterns of the obtained crystals prove the garnet structure without any evident second phase. The characteristic Ce3+ emission located at around 540 nm was presented in the photoluminescence and X-ray excited luminescence spectra. The scintillation light yield reaches up to 34 132 pho MeV−1 and scintillation decay time was optimized to 64 ns with a high fast decay component of about 85%. The TSFZ method demonstrated the growth feasibility of Ce:GGAG crystals that have an incongruent-melting trend with lower Ga/Al ratio in the compositions. [ABSTRACT FROM AUTHOR]

Because of their potential low cost, bright light, and fast decay time, LuAG:Ce ceramic scintillators have attracted a broad interest in the high-energy physics community. One crucial issue for their application in future high-energy physics experiments is their radiation hardness against neutrons and protons expected at future hadron colliders. We report optical and scintillation performance of 1-mm LuAG:Ce ceramic samples doped with Mg2+ (and Ca2+) and their radiation damage induced by hadrons. While Mg2+ co-doping improves their light output, Ca2+ co-doping improves their fast to total (F/T) ratio. LuAG:Ce ceramic samples were irradiated at the Los Alamos Neutron Science Center (LANSCE), Los Alamos, NM, USA, by neutrons up to $6.7\times 10^{15}\,\,\text{n}_{\mathrm {eq}}$ /cm2 and by 24-GeV and 800-MeV protons at CERN PS-IRRAD up to $1.2\times 10^{15}$ p/cm2 and at LANSCE up to $2.3\times 10^{14}$ p/cm2, respectively. All samples show excellent radiation hardness with more than 90% of light after irradiation. The RIAC values induced by neutrons are found to be a factor of 2 smaller than lutetium–yttrium oxyorthosilicate (LYSO:Ce) crystals. The RIAC values induced by protons are also found a factor of 2 smaller than LYSO:Ce crystals in LuAG:Ce ceramic samples with good optical quality. Research and development will continue to develop LuAG:Ce scintillating ceramics with improved optical quality for future investigation. [ABSTRACT FROM AUTHOR]

Gamma/neutron dual detection has occupied significant territory in the field of homeland security and nuclear energy development. Cs2LiLaBr6 (CLLB) has shown both neutron/gamma dual-mode detection capability and excellent scintillation properties. Herein, we explored the Cs2LaBr5-LiBr phase diagram through powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC) tests of synthesized polycrystalline materials. The Cs2LaBr5-rich side of the phase diagram is similar to a binary peritectic phase diagram, where the peritectic line (447 °C) extends to a LiBr content of 61%. The LiBr-rich side of the phase diagram resembles a binary eutectic phase diagram, where the eutectic point (395 °C) is located at 80% LiBr concentration. Guided by the phase diagram, CLLB ingots were designed to grow from the LiBr-rich side with different concentrations of LiBr. The scintillator properties of CLLB crystals were found to be deteriorated by the increasing defects with elevated LiBr contents. A concentration of LiBr around 55% was a preference for the growth of high-quality CLLB. A better understanding of the Cs2LaBr5-LiBr phase diagram benefits the growth of CLLB crystals and provides considerations for other halide double perovskites. [ABSTRACT FROM AUTHOR]

The development of Eu2+-activated oxide materials with high efficiency, fast decay and narrow bandwidth emission in the visible region is still challenging for the field of luminescence and scintillation applications. Generally, Eu2+ in oxide hosts can emit intense and broad 5d-4f emission in the visible region, but efficient emitting with stable bivalence of Eu is rare in inorganic oxide system. In this work, a series of ASL:Eu2+ (Sr 1-x La x Mg x Al 12-x O 19) powder samples with various La, Mg doping ratios were designed and synthesized to modulate the UV or X-ray excited luminescence properties, including redshift, quantum yield, and decaying lifetime. Moreover, an ASL:Eu2+ crystal with the optimal ratio x = 1/3 was grown, its scintillation performance was compared with standard Bi 4 Ge 3 O 12 crystal sample and evaluated in detail. These results indicate that the ASL:Eu2+ crystal is potential scintillator as a kind of X-ray detection and provide a reference for the further development of high-performance Eu-activated oxide scintillation materials. • The La, Mg dopants in SrAl 12 O 19 host promotes the red shift of Eu2+ emission under UV excitation. • The ASL:Eu2+ shows the self-trapped excitons radiation in XEL spectra. • The light yield of the as-grown ASL:Eu2+ crystal was determine to be 111.6 p.e./MeV. [ABSTRACT FROM AUTHOR]

• (Gd 1-x Ce x) 3 (Ga 0.995 Cr 0.005) 5 O 12 single crystals were grown by micro-pulling down method. • The emission wavelengths of these crystals were approximately 730 nm. • Cr was segregated in the center part of the crystals. • The relationship between Cr segregation and emission intensity was investigated. • The correlation coefficients of thoes relationships were around 0.9. For the decommissioning of Fukushima Daiichi Nuclear Plants, a novel real-time dose-rate monitor consisting of a scintillator, 100-m long optical fiber and CCD spectrometer has been proposed, and this scintillation material is required to have an emission wavelength of longer than approximately 650 nm. In this paper, as a candidate material for the system, we focused on Ce/Cr co-doped Gd 3 Ga 5 O 12 (Ce/Cr:GGG) single crystals grown by the micro-pulling down method. Since the light output of this material was expected to depend on the Cr3+ concentration, we investigated the relationship between Cr segregation and luminescence properties in Ce/Cr:GGG crystal. Generally, a single photon counting method is not available to evaluate its light output accurately due to the long decay time, we used a novel technique "emission-intensity two-dimensional- mapping method" (2D-image method) to verify the light intensity at each point of the sample. This method realized estimation of the light intensity within the sample, though segregation of Cr3+ is observed. The results showed that Cr was concentrated in the center part along the radial direction in the grown crystals, while all parts had an emission wavelength of approximately 730 nm excited by X-ray. Using the 2D-image method, emission intensity was found to correspond to the Cr concentration, and its correlation coefficients between emission intensity and Cr concentration were over 0.8. We found that our material is available for the monitoring system when the Cr dense part of the crystal is cut and used. [ABSTRACT FROM AUTHOR]

• Crystal growth of CsMgF 3 by micro-pulling-down method was investigated. • Contrary to published equilibrium phase diagram Cs 4 Mg 3 F 10 was a stable phase. • Due to evaporation, excess CsF was required to grow transparent Cs4Mg3F10 crystals. • Scintillation properties of Cs 4 Mg 3 F 10 were measured. In our search for cross-luminescence (CL) scintillators suitable for fast-timing applications, we have chosen CsMgF 3 as one of the perspective candidates. During the attempts to grow CsMgF 3 by the micro-pulling-down method, we have revealed the presence of Cs 4 Mg 3 F 10 which is in contradiction with the published equilibrium phase diagram. The Cs 4 Mg 3 F 10 has an orthorhombic structure, consisting of face-sharing MgF 6 octahedra triplets (4 triplets per unit cell), joined to 4 other triplets by corner sharing. These chain-like structures are separated by Cs+ ions. Moreover, Cs 4 Mg 3 F 10 is non-hygroscopic despite the hygroscopic nature of CsF. The best crystals were grown from CsF-rich melt to suppress off-stoichiometry due to CsF evaporation during crystal growth. Both radioluminescence spectra and scintillation decay kinetics exhibit complex character and the presence of CL in Cs 4 Mg 3 F 10 is still under question. However, due to relatively low scintillation efficiency and the presence of slow components in scintillation decay, Cs 4 Mg 3 F 10 is not suitable for fast-timing applications. [ABSTRACT FROM AUTHOR]

The research investigates coherent interactions between sub-GeV electrons and oriented scintillator crystals, leading to enhanced electromagnetic (EM) radiation. Experiments at Mainz Mikrotron (MAMI) involved PWO, BGO, and CsI crystals oriented along 〈 100 〉 , 〈 111 〉 , and 〈 100 〉 axes, respectively. Enhanced radiation emission was observed when the beam was aligned with crystal axes, especially in BGO and CsI for the first time. These findings are crucial for innovative detectors using oriented crystal scintillators, amplifying EM processes along specific crystallographic directions. Potential applications include ultra-compact, highly sensitive electromagnetic calorimeters for high-energy physics and astroparticles, as well as high-performance gamma detectors for nuclear physics and medical imaging. [ABSTRACT FROM AUTHOR]

(C 6 H 5 C 2 H 4 NH 3) 2 Pb 1- x Ca x Br 4 (x = 0.05, 0.1, and 0.25) crystals were grown by the solvent diffusion method and evaluated for the photoluminescence and scintillation properties. When irradiated by X-rays, emission peaking at 440 nm due to exciton emission was observed. The pulse height spectra of (C 6 H 5 C 2 H 4 NH 3) 2 Pb 1- x Ca x Br 4 under 137Cs γ-ray irradiation demonstrate that the light yields were 20,000, 17,000, and 16,000 ph/MeV in x = 0.05, 0.1, and 0.25 samples, respectively. Ca-substitution significantly enhances the photoluminescence quantum yield and scintillation light yield. • (C 6 H 5 C 2 H 4 NH 3) 2 (Pb,Ca)Br 4 crystals were evaluated for the photoluminescence and scintillation properties. • (C 6 H 5 C 2 H 4 NH 3) 2 (Pb,Ca)Br 4 crystals exhibit a sharp emission peaking at 440 nm due to exciton luminescence. • Pulse height spectra under 137Cs γ-rays demonstrate the light yields was 20,000 ph/MeV. • Ca-substitution enhances both the photoluminescence and scintillation properties. [ABSTRACT FROM AUTHOR]

ZnO:Ga (GZO), as well as other band-edge luminous materials, exhibits fast time response properties, which makes it suitable for application as an ultraviolet scintillator for transient radiation detection. However, due to the serious self-absorption problem and low external quantum efficiency, the luminescence intensity cannot be intensified by increasing the volume of the crystals. To alleviate this problem, CsPbBr 3 quantum dot (QD) films were used to enhance the radioluminescence (RL) intensity of GZO. The effects of CsPbBr 3 QD films on the emission spectrum, intensity and angular distribution were experimentally analyzed under three different modes, namely, coating on the imaging surface, incident surface and both surfaces. The CsPbBr 3 QD film on the imaging surface could change the external quantum efficiency and luminescence angular distribution of GZO via its various surface morphologies. When CsPbBr 3 QD films were coated on both surfaces, the luminescence intensity reached 2.43 times that of GZO, while the proportion of emitted light from GZO was less than 6 %. Based on the experimental results, the principle of the enhancement and the difference among the three coating modes were discussed. The enhancement caused by CsPbBr 3 QD films on GZO was considerable and could be simply duplicated on many other materials, expanding their application in the field of detection and imaging. • Radioluminescence intensity of ZnO:Ga can be enhanced by coating perovskite films. • Scintillation performance of CsPbBr 3 QD film-coated ZnO:Ga was investigated. • Tuning the angular distribution by CsPbBr 3 QD film is beneficial for X-ray imaging. [ABSTRACT FROM AUTHOR]

Lanthanide doped fluoride scintillators possess a diverse range of applications in the fields of computed tomography and medical imaging. In this study, CsLu 2 F 7 : Pr crystals have been synthesized by a simple hydrothermal method to realize X-ray excited optical luminescence (XEOL). Our results reveal that the reaction temperature and amount of cetyltrimethylammonium bromide (CTAB) can significantly change the morphology of the crystals; the suitable hydrothermal reaction conditions, the amount of CTAB, and the doping concentration of Pr3+ ions are favorable for the enhancement of the XEOL intensity; and the crystals exhibit good irradiation stability under prolonged X-ray excitation. In addition, we used the crystal to prepare scintillation films to realize XEOL imaging. This research provides crucial information to support an in-depth investigation into the XEOL performances of CsLu 2 F 7 doped with lanthanide ions. • CsLu 2 F 7 : Pr crystals were synthesized using a hydrothermal method. • The morphology was adjusted by changing the reaction temperature and CTAB. • CsLu 2 F 7 : Pr involved film can be used for X-ray imaging. [ABSTRACT FROM AUTHOR]

• Li 4 Mo 5 O 17 crystals were grown by low-thermal-gradient Czochralski technique. • DSC and XRD studies showed single Li 4 Mo 5 O 17 phase. • According to SCXRD study Li 4 Mo 5 O 17 belongs to triclinic P-1 space group. • Photoluminescence was registered with peak maximums at 670 nm (370 nm excitation) and 645 nm (300 nm excitation). Transparent Li 4 Mo 5 O 17 crystals with dimensions 60 × 30 × 20 mm were grown by low-thermal-gradient Czochralski technique. Optimal growth parameters were determined. According to SCXRD, Li 4 Mo 5 O 17 compound crystallizes in the triclinic space group of P 1 ¯ and the unit cell parameters at 150 K are a = 6.7596(2) Å, b = 9.4546(3) Å, c = 10.7909(3) Å, α = 73.1610(10)°, β = 88.8810(10)°, γ = 69.7460(10)°, V = 616.75(3) Å3. Uniformity of obtained crystals was confirmed by XRD analysis. Li 4 Mo 5 O 17 crystal structure and cell parameters were studied by SCXRD. Li 4 Mo 5 O 17 melting point at 546 °C was determined by DSC curve in 300–1000 K range. Luminescence was registered with peak maximum 670 nm at 370 nm excitation and 645 nm at 300 nm excitation. [ABSTRACT FROM AUTHOR]

C s 3 C u 2 I 5 : T l is a novel scintillator boasting high density, a substantial light yield, and excellent energy resolution, making it promising for applications in gamma-ray spectroscopy. In this paper, we developed a multi-functional melt growth furnace capable of convenient configuration for the Czochralski (Cz), Edge-defined Film-fed (EFG), and Bridgman methods. We successfully grew C s 3 C u 2 I 5 : T l crystals using the Cz, EFG, and Bridgman methods, yielding crystal sizes of Φ 15 mm, Φ 12 mm, and Φ 30 mm, respectively. The obtained crystals exhibit satisfactory crystalline quality, although they are susceptible to cracks during the cooling, cutting, and polishing processes. Samples are taken from the crystals to undergo analysis to investigate their optical and scintillation properties. Findings indicate that our C s 3 C u 2 I 5 : T l possess a large Stokes shift of 175 nm with nearly no spectral overlap between the PLE and PL spectra. The radioluminescence emission peaked at 505 nm, accompanied by a scintillation decay time of 828 ns. The samples exhibited a commendable energy resolution of 4.8% at 662 KeV and a high light yield of 83000 ph/MeV when coupled with a PMT. This study validates the viability of employing CZ and EFG methods for the growth of C s 3 C u 2 I 5 : T l crystal, in addition to showcasing the Bridgman method for the growth of centimeter-scale C s 3 C u 2 I 5 : T l crystals. • Development of a multi-functional for the melt growth of metal halide crystals. • Growth of centimeter-sized C s 3 C u 2 I 5 : T l crystals by Cz, EFG, and Bridgman methods. • The as-grown C s 3 C u 2 I 5 : T l has 83000 ph/MeV light yield and 4.8% energy resolution. • C s 3 C u 2 I 5 : T l crystals grown by Cz, EFG, and Bridgman show similar performances. [ABSTRACT FROM AUTHOR]

This work is dedicated to investigation of the luminescent properties of the prospective photoconversion material based on the crystal of Ce3+ doped Ca 3 Sc 2 Si 3 O 12 (CSSG) garnet. The GSSG:Ce crystal was grown using the micro-pulling-down (μPD) method. The CSSG:Ce crystal exhibited an intensive photoluminescence (PL) emission band with two sub-bands peaked at 504 and 545 nm, corresponding to 5d-4f (2F 5/2;7/2) transitions. Furthermore, we have investigated also the formation of cerium multicenters in the GSSG:Ce crystal using analyses of the structure of Ce3+ photoluminescence emission and excitation spectra under excitation of the luminescence of this crystal by synchrotron radiation. The formation of Ce3+-multicenters in CSSG:Ce garnet is caused by the local inhomogeneity of the dodecahedral sites of garnet lattice due to localization of the hetero-valent Sc3+ and Si4+ cations in the octahedral and tetrahedral positions of the garnet host. The existence of Ce3+ multicenters resulted in a significant enhancement of the Ce3+ emission band in the red range and improving the performance of conventional YAG:Ce phosphor. The next task of our work was to evaluate the possibility of application of the GSSG:Ce crystal as a light phosphor-converter (pc) for white light-emitting diodes (WLEDs). In the frame of this task, we have successfully developed a prototype of WLED by employing the CSSG:Ce crystal as a phosphor-converter (pc) with blue 450 emitting LED as well as investigated the color characteristics of this pc-WLED. • Ca 3 Sc 2 Si 3 O 12 :Ce (CSSG:Ce) crystal was grown by micropulling down method. • Presence of two different Ce1 and Ce2 emission centers was detected CSSG:Ce crystals. • Luminescent properties and energy structure of F+ and F centers in CSSG host were studied. • Prototypes of a white LED based on CSSG:Ce phosphor and blue LED were developed. [ABSTRACT FROM AUTHOR]

Monitoring the level of radioactive contamination and the type of radiation in the environment is very important for the protection of facilities, employees, and people. Phoswich detector is one of the useful tools to identify different radiations and separate them from each other using different scintillating crystals. However, their design can be very diverse based on the type of particles analyzed and various parameters of scintillating crystals and needs optimization to have maximum efficiency. This work aims to optimize the scintillating crystal layers for the design of the three-layer alpha-beta-gamma phoswich detector based on Monte Carlo radiation transport calculations. The selection of the appropriate model for the type and thickness of each layer is based on the optimization of parameters such as energy accumulation, produced scintillation optical photons, attenuation of optical photons, and scintillation decay time. The results showed that the three scintillating layers of ZnS(Ag), CaF 2 (Eu), and LYSO(Ce) with optimal thicknesses of 25.01 μm, 3.50 mm, and 2.54 cm, respectively, have more suitable optical outputs for detecting common alpha-beta-gamma radionuclide emitters. • Different scintillating crystals were investigated for various radiations. • Modeling of three-layer scintillating crystal layers was carried out. • An optimal configuration for a phoswich detecting alpha-beta-gamma was obtained. • Monte Carlo calculation was used to investigate phoswich parameters. [ABSTRACT FROM AUTHOR]

An ion implanter was used to irradiate protons with a dose of 8×1016 ions/cm2 and an energy of 400 keV into a Ce3+:GGG crystal. To our knowledge, this is the first time that ion implantation was applied to a Ce3+:GGG crystal. The penetration depth was determined by the stopping and range of ions in matter simulation. The prism coupling method was utilized to evaluate the propagation modes in the H+-implanted waveguide. The end-face coupling method and the finite-difference beam propagation were employed for the analysis of the waveguide performance. The refractive index distribution was reconstructed by the reflectivity calculation method. The main significance of the investigation is to confirm the potential of the ion-irradiated Ce3+:GGG crystals for fabricating waveguide structures and devices. [ABSTRACT FROM AUTHOR]

Luminescence and scintillation properties of Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,Mg (0.02, 0.05 %) garnet crystals grown by the micro-pulling down method were investigated. The onset temperature for luminescence quenching at ∼365 K is determined from the temperature dependence of photoluminescence decay time. At room temperature, the Mg (0.05 %) sample exhibits high integral scintillation efficiency of ∼445 % of BGO crystal, light yield value of 23,500 photons/MeV, and fast scintillation decay times of 20 ns (15 %) + 54 ns (85 %). The higher radioluminescence intensity of the Mg (0.05 %) sample correlates with an appearance of its lower themally-stimulated luminescence intensity in 77–500 K range. • Luminescence and scintillation properties of Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,Mg (Mg = 0.02 %, 0.05 %) crystals are investigated. • Both crystals show onset of luminescence quenching at 365 K. • Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,0.05%Mg shows light yield of 23,500 photons/MeV. • Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,0.05%Mg shows scintillation decay time of 20 ns (14 %) + 54 ns (86 %). • Thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

The HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission aims to develop a constellation of nanosatellites to study astronomical transient sources, such as gamma-ray bursts, in the X and soft γ energy range, exploiting a novel inorganic scintillator. This study presents the results obtained describing, with an empirical model, the unusually intense and long-lasting residual emission of the GAGG:Ce scintillating crystal after irradiating it with high energy protons (70 MeV) and ultraviolet light (∼ 300 nm). From the model so derived, the consequences of this residual luminescence for the detector performance in operational conditions has been analysed. The suitability of this detector for the HERMES Pathfinder nanosatellites was demonstrated by the low contribution of the afterglow, 1–2 pA at peak, to the input current of the front-end electronics. [ABSTRACT FROM AUTHOR]

To precisely characterize the defects in crystalline solids including semiconductors and alloys, it is critical but challenging to improve the time resolution of positron annihilation lifetime (PAL) spectrometers. The effects of geometry and wrapping of scintillators on the time resolution of the PAL spectrometer were studied in detail. Geant4 program simulation was used to clarify the reason why cone-frustum-shaped scintillators have better time resolution than cylinder-shaped scintillators. A figure of merit was proposed to comprehensively evaluate the impacts of the transport and absorption of fluorescent photons on the time resolution of scintillators. Additionally, for the simulations of cone-frustum-shaped scintillators, polished reflective coatings can further improve the time resolution without losing count rate. Eventually, using three cone-frustum-shaped Ba F 2 scintillators and a double-stop setup, we significantly improved the time resolution of PAL spectrometer to a new record of 88.7 ps, the best time resolution up to date. This enables us to distinguish various vacancy types in crystalline solids more precisely in future. • Explained why cone-frustum-shaped scintillators have better time resolution. • Proposed a figure of merit to evaluate the time resolution of PAL spectrometer. • Achieved the best time resolution up to date for the PAL spectrometer. [ABSTRACT FROM AUTHOR]

(K,Rb) 2 CuBr 3 crystals were fabricated by the slow cooling method, and their photoluminescence (PL) and scintillation properties were examined. Emission bands were observed at 350–550 nm under UV and X-ray irradiation. PL quantum yields of K 2 CuBr 3 , (K 0.25 ,Rb 0.75) 2 CuBr 3 , (K 0.5 ,Rb 0.5) 2 CuBr 3 , (K 0.75 ,Rb 0.25) 2 CuBr 3 , and Rb 2 CuBr 3 were respectively 75.8, 71.0, 82.3, 96.9, and 96.3%. The scintillation decay curves were approximated by a sum of three exponential functions, and the decay time constants due to recombination of self-trapped excitons were 58–63 μs. The afterglow levels of the K and Rb-mixed samples at 20 ms passed after X-ray irradiation decreased to 10–40 ppm, compared with those of K 2 CuBr 3 and Rb 2 CuBr 3. Among these samples, (K 0.75 , Rb 0.25) 2 CuBr 3 showed the highest light yield of 7400 ph/MeV among the samples calculated from the pulse height spectra of 137Cs γ-rays (662 keV). • (K,Rb) 2 CuBr 3 crystals were synthesized by the slow cooling method. • The afterglow levels of the (K,Rb) 2 CuBr 3 were 10–40 ppm. • (K 0.75 ,Rb 0.25) 2 CuBr 3 showed the highest light yield (7400 ph/MeV) in prepared samples. [ABSTRACT FROM AUTHOR]

The ORION chipset, a full-custom multichip readout and processing electronics for the X- $\gamma $ -ray imaging spectrometer (XGIS) on-board the transient high-energy sky and early universe surveyor (THESEUS) space mission, is presented. The XGIS detection plane is arranged in a matrix of 10 $\times $ 10 detection modules, each one composed of 64 CsI(Tl) scintillation bars (4.5 mm $\times $ 4.5 mm $\times $ 30 mm) optically coupled at the top and bottom ends to two 8 $\times $ 8 monolithic silicon drift detector (SDD) matrices. The top SDD, exposed to the X-ray entrance window, performs the double function of low-energy X-ray detection as well as scintillator’s readout, together with the bottom SDD, providing detection and spectroscopic energy range from 2 keV up to 20 MeV. The need to achieve a high-energy resolution, as well as a high sensitive area on the detection plane, led to the development of a chipset organized to have a minimum-area analog readout chip placed in close proximity of the SDD (ORION-FE) and a mixed-signal back-end (ORION-BE) placed a few centimeters further on the back-end board for the additional signal processing and digitization. The multichip readout electronics integrates two dedicated analog processors for low-energy photons up to 30 keV (X-processor) and high-energy photons up to 5 MeV ($\gamma $ -processor), allowing a spectroscopy-grade resolution in the 4 decades energy band (2 keV–20 MeV) of the XGIS, with a simulated power consumption of 1.55 mW/pixel. The ORION prototype was bonded to two ~25 mm2 SDDs, and extensively characterized in terms of pulse shaping, pulse discrimination, and stretching functionality, as well as linearity, dynamic range, and spectroscopic resolution. An optimum equivalent noise charge (ENC) at −20 °C of 24.3 el. r.m.s. on the X-channel [212 eV full-width at half-maximum (FWHM) on Si], and 39.6 el. r.m.s. on the $\gamma $ -channel [3.7 keV FWHM on CsI(Tl)] has been recorded. [ABSTRACT FROM AUTHOR]