Excellent Scintillation Research Articles

Dramatically Enhanced X-ray Scintillation of BODIPY via Sensitization by an Organic Metal Halide

X-ray scintillators based on organic chromophores have the potential to deliver low-cost radiation detection products with fast response signals. However, their relatively low performance compared with that of widely used inorganic scintillators in terms of X-ray attenuation and light output has limited their applications. Here we report a dramatically improved scintillation performance for a BODIPY dye, difluoro(4-(1,1-dimethylethyl)-2-{1-[4-1,1-dimethylethyl)-3,5-dimethyl-2H-pyrrol-2-ylidene-N] ethyl-3,5-dimethyl-1H-pyrrol-2-ylidene-N] ethyl}-3,5-dimethyl-1H-pyrrolato-N) boron (PM 570), via sensitization by a 0D organic metal halide, tetraphenylphosphonium manganese bromide ((C24H20P)2MnBr4). By blending PM 570 and (C24H20P)2MnBr4 in an appropriate ratio together in a polydimethylsiloxane matrix, we prepare plastic scintillators to exhibit a more than 15-fold increment of radioluminescence from PM 570. Such an enhancement is attributed to the excellent X-ray scintillation property of (C24H20P)2MnBr4 and the efficient energy transfer from (C24H20P)2MnBr4 to PM 570. These multicomponent plastic scintillators also exhibit an excellent linear response to the X-ray dose rate and a low detection limit of 22.5 nGy s–1.

Improvements in scintillation performance of Tl2LaCl5:5%Ce single crystals via Sr2+, Ba2+ and Ca2+ co-doping

High detection efficiency for X- and γ-rays, fast neutron detection capability, and other excellent scintillation performances of Tl2LaCl5 (TLC) make it a potential radiation detector for applications in various industrial and research field.

Stable and Bright Commercial CsPbBr3 Quantum Dot-Resin Layers for Apparent X-ray Imaging Screen.

CsPbBr3 quantum dots (QDs) have recently gained much interest due to their excellent optical and scintillation properties and their potential for X-ray imaging applications. In this study, we blended CsPbBr3 QDs with resin at different QD concentrations to achieve thick films and to protect the CsPbBr3 QDs from environmental moisture. Then, their scintillation properties are investigated and compared to the traditional commercial scintillators, CsI:Tl microcolumns, and Gadox layers. The CsPbBr3 QD-resin sheets show a high light yield of up to 21 500 photons/MeV at room temperature and a relatively small variation in light yield across a wide temperature range. In addition, the CsPbBr3 QD-resin sheets feature a small scintillation afterglow. The CsPbBr3 QD-resin sheets show a negligible trap density for the concentration below 50% weight, indicating that traps might arise from the aggregation of the QDs. The CsPbBr3 QD-resin sheets are also very stable at low irradiation intensities and relatively stable at higher intensities, with higher CsPbBr3 QD concentrations being more stable. Gamma-ray-excited-time-resolved emission measurements at 662 keV showed that the CsPbBr3 QD-resin sheets have an average scintillation decay time between 108 and 176 ns, which are still 10 000 and 6000 times faster than CsI:Tl and Gadox, respectively. Imaging tests show that the CsPbBr3 QD-resin sheets have a mean transfer function of 50% at 2 lp/mm and 20% at 4 lp/mm, comparable to that of commercial Gadox layers. This feature makes CsPbBr3 QD-resin sheets a good candidate for the low-cost, flexible X-ray imaging screens and γ-ray applications.

The ASTAROTH Project: enhanced low-energy sensitivity to Dark Matter annual modulation

ASTAROTH is a novel R&D project which aims at improving the physics reach of future direct dark matter detection experiments based on NaI(Tl) scintillating crystals. There is a strong need to test the long standing DAMA positive observation of an annual modulation that could be due to Dark Matter (DM), with the same target material and in a model independent way. ASTAROTH aim is the enhancement of the sensitivity to the annual modulation signal, compared with present technology, by lowering the detection energy threshold in order to observe sub-keV recoils for the first time. This can be achieved by reading the scintillation light from the NaI(Tl) crystals with arrays of Silicon PhotoMultipliers (SiPM), and placing the detectors in a cryogenic environment. SiPMs feature lower dark noise than Photomultiplier Tubes (PMTs) at T < 150 K and allow for higher light collection. The cooling medium is liquid Argon, as it is an excellent scintillator that can be instrumented to act as a veto against several backgrounds.Here we present the status of the ASTAROTH project, introducing the innovative design of the detector chamber that will be used for the demonstration of the technology. Then, we will show the preliminary results of our first ever measurements performed on a single NaI(Tl) crystal read out by one SiPM array in a cryogenic set-up cooled with liquid nitrogen.

Growth and Characterization of Ce-Doped Luag Single Crystal Fibers from Transparent Ceramics by Laser-Heated Pedestal Method

Scintillation single crystal fibers (SCFs) have great potential applications in the new generation of high-energy ray and particle detectors due to their morphological advantages. In this work; Ce:LuAG SCFs with a diameter of 1 mm were grown along the direction of [111] by laser-heated pedestal growth (LHPG) method using a transparent ceramic as the source rod; and a doping concentration was 0.1 at%, 0.3 at%, 1 at%, respectively. The effects of growth rate and annealing in air on the scintillation and optical properties of SCF are discussed in detail. The results of analyzing the absorption spectra; radioluminescence (RL) spectra; pulse-height spectra and fluorescence lifetime of SCFs show that the SCF maintains excellent scintillation performance while having a fiber structure. Therefore; Ce:LuAG SCF is a potential candidate material for detector.

Electronic and optical properties and upper light yield estimation of new scintillating material [formula omitted]: Ab initio study

Based on the density functional theory, this work reports an Ab initio investigation on the electronic and optical properties as well as the upper light yield estimation of the new scintillating material TlMgCl3. The DFT calculations are performed with the help of the FP-LAPW method using GGA and GGA + mBJ approximations as well to ensure a reliable band gap and accurate electronic band structure and optical properties. The computed band structure and density of states indicate that, this material has a direct band gap of 6.04 eV at M point. By including the spin–orbit coupling (GGA + mBJ + SOC), a similar direct band gap is obtained but with a value equals to 5.74 eV, due to the splitting of Tl 6p states at the bottom of the conduction band. Moreover, this coupling changes the conduction band and creates a very small gap and dips which enhance the intra-band radiative transitions. Additionally, the imaginary part of the dielectric function, reflectivity, absorption coefficient, and the refractive index along × and z directions are calculated and discussed in the two cases: GGA + mBJ and GGA + mBJ + SOC. Precisely, the obtained results demonstrate that, this material has a high rate of transmittance greater than 92.5% in the emission range. Besides this, the upper light yield (LYsc) in the ideal conditions, with a limit of 100%, is estimated in these two cases to be 66,225 ph/MeV and 69,686 ph/MeV, respectively. These findings contribute to explain the reason behind the excellent scintillation properties of TlMgCl3 and make this material a good candidate for scintillation detectors applications.

Neutron-induced point defects and luminescence properties of enriched Zn82Se crystals

Enriched Zn82Se is a very promising material for the detection of the neutrionoless double beta decay. The 82Se isotope acts as the source of the decay, and ZnSe detects the scintillation and bolometric events. Due to the high cost in the preparation of the Zn82Se material, the optimization of its properties, especially those related to the scintillation process, is mandatory. It is well known that excellent scintillation efficiency in ZnSe is obtained when the material presents close donor–acceptor pairs, as, for example, the A-centers. In this work, neutron irradiation was used to study formation of point defects in enriched and non-enriched ZnSe samples. Applying instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectroscopy, the enrichment of Zn82Se samples was determined to ∼95%, in addition, trace impurities such as Cu, I, and Na were quantified by INAA at the μg/g level. Based on electron paramagnetic resonance (EPR) and photo-EPR measurements, we show that irradiation with fast neutrons induced point defects such as the isolated zinc vacancy (VZn) and a new low-symmetric donor center called NC1, which we tentatively assign to Zn di-interstitials. Low-temperature photoluminescence measurements of the neutron-irradiated Zn82Se revealed three broad PL bands centered in the visible spectral range. Based on the INAA analysis shown in this work, we attribute the previously unidentified 540 nm PL band in the Zn82Se sample to recombination between shallow donors and deep copper acceptors. The formation of point defects by neutron irradiation and their stability are discussed.

Study on the optical properties of CdWO4 crystal with oxygen vacancies

Cadmium tungstate crystals have attracted much attention because of its excellent scintillation performance. The existence of oxygen vacancies will reduce the luminous efficiency of the crystal, extend its luminous decay time and reduce light resolution of the crystal. However, the luminescence mechanism of the oxygen vacancies is not clear yet. Here, the optical properties of cadmium tungstate crystal with oxygen vacancies have been studied based on the Density Functional Theory (DFT). We calculated the defect formation energies of oxygen vacancies with three different charges (0, +1, +2), and corrected the band gap to make it more accurate. We obtained the absorption and emission peaks of the F center and F+ center for two different types of oxygen vacancies. The calculated absorption peaks of the F center of VOI and F+ center of VOII at 3.04 eV and 3.59 eV respectively, which are close to the experimental results (3.1 eV (400 nm) and 3.5 eV (350 nm)). So we speculate that these two obvious absorption peaks are caused by oxygen vacancies.

Luminescent properties and X-ray imaging result of Lu2O3:Eu structured scintillation film on YSZ single crystal substrate by LCVD method

Micro-columnar structured europium doped lutecia (Lu2O3:Eu) scintillation film is one of the most attractive candidate materials for high-energy hard X-ray imaging detectors because of their excellent physical, scintillation properties and light guide effect. Lu2O3:Eu micro-columnar film (MCF) with 9 μm thickness was obtained on a yttrium stabilized zirconia (YSZ) (100) single crystal substrate by laser chemical vapor deposition (LCVD), and its structure, morphology, photoluminescence and scintillation properties were characterized. The structure and morphology of obtained film were investigated by grazing incidence X-ray diffraction (GIXRD) and scan electron microscopy (SEM). The photoluminescence and scintillation properties, including photoluminescence excitation (PLE), photoluminescence (PL), PL decay, X-ray excited luminescence (XEL), were measured and discussed. The X-ray imaging result of Lu2O3:Eu MCF on YSZ substrate was obtained for the first time and spatial resolution of 2 μm was obtained at BL13W beamline at Shanghai synchrotron radiation facility (SSRF).

Review of Liquid Argon Detector Technologies in the Neutrino Sector

Liquid Argon (LAr) is one of the most widely used scintillators in particle detection, due to its low cost, high availability and excellent scintillation properties. A large number of experiments in the neutrino sector are based around using LAr in one or more Time Projection Chambers (TPCs), leading to high resolution three-dimensional particle reconstruction. In this paper, we review and summarise a number of these Liquid Argon Time Projection Chamber (LArTPC) experiments, and briefly describe the specific technologies that they currently employ. This includes single phase LAr experiments (ICARUS T600, MicroBooNE, SBND, LArIAT, DUNE-SP, ProtoDUNE-SP, ArgonCube and Vertical Drift) and dual phase LAr experiments (DUNE-DP, WA105, ProtoDUNE-DP and ARIADNE). We also discuss some new avenues of research in the field of LArTPC readout, which show potential for wide-scale use in the near future.

Characterization of Eu-doped Ba2SiO4, a high light yield scintillator

Photoluminescence and scintillation characteristics of Eu-doped Ba2SiO4 were investigated. A broad emission band due to Eu2+ is observed at 500 nm, and the photoluminescence and radioluminescence decay time constants are about 397 and 515 ns, respectively. From the pulse height distribution of 57Co γ-rays, the light yield of Eu:Ba2SiO4 is ∼48 000 ph MeV−1, which is comparable with those of developed oxide scintillators showing a high light yield. The results demonstrate that Eu-doped Ba2SiO4 is a high-performance scintillator for X- and γ-ray measurements and characterized by excellent scintillation output and afterglow.

Improved Phase Stability and Enhanced Luminescence of Calcite Phase LuBO3:Ce3+ through Ga3+ Incorporation.

The application of LuBO3:Ce3+ (LBO:Ce) crystal as an excellent scintillation material has been limited due to its poor phase stability at high temperature or high pressure, so improving the phase stability is essential for promoting its development. Ga stabilized LuBO3:Ce3+ (LGBO:Ce) is synthesized by solid-state reaction at 1200 °C. Powder X-ray diffraction patterns and Raman spectra at ambient pressure show that all the samples are pure calcite phase. In situ high-pressure synchrotron radiation XRD patterns illustrate that calcite phase LGBO:Ce exhibits more excellent phase stability than that of LBO:Ce under high pressure due to the superior compressibility of the [GaO6] octahedral unit. The optical band gap of LGBO decreases from 5.58 to 4.64 eV after introducing 10% Ga, which leads to the decreased nonradiative transition and about double luminescence intensity as expected. More interestingly, the charge transition from O2- to Ce4+ is observed at about 290 nm in the absorption spectra. The X-ray photoelectron spectroscopy spectra indicate the ratio of Ce4+/Ce3+ increases with increasing concentration of Ga3+, which can be attributed to the variation of energy separation between the 4f ground state of Ce3+ and the Fermi energy level position. In contrast to the enhancement of PL intensity, the integrated X-ray excited luminescence intensity decreases after Ga3+ incorporation attributing to the result of both decreased effective atomic number and ionization energy between 5d1 level and conduction band. The thermal luminescence spectra show that after the incorporation of Ga3+ the oxygen vacancy and intrinsic defects in LBO remain unchanged but that the concentration of oxygen vacancy significantly reduces. The mechanism of Ga3+ incorporation on phase stability and luminescence properties of LBO:Ce has been proposed and discussed systematically.

New Efficient Scintillating and Photoconversion Materials Based on the Self‐Flux Grown Tb3Al5O12:Ce Single Crystal

This research deals with a novel approach for the self‐flux growth of Tb3Al5O12:Ce single crystal using the micro‐pulling‐down method. The self‐flux method enables the fabrication of the crystals with excellent photoconversion and scintillation properties. Tb3Al5O12:Ce (TbAG:Ce) efficiently converts the blue light‐emitting diode (LED) radiation into bright white light. The gradual change of crystal thicknesses (0.2–1 mm) allows for tuning white light temperature from cold to neutral white. The scintillation response is comparable with that of a high‐quality single crystalline film counterpart with a light yield value of around 4500 photons MeV−1 under α particle excitation from 239 Pu radioisotope. This is the highest value obtained for the TbAG:Ce crystal yet.

Discovery, Crystal Growth, and Scintillation Properties of Novel Tl‐Based Scintillators

AbstractPioneered by our group, thallium (Tl)‐based inorganic halide single‐crystals are potential new scintillators. Most of these scintillators exhibit excellent scintillation performance, including peak emission between 370 and 450 nm, good energy resolutions, high light yield (more than 50 000 ph MeV‐1) and fast decay‐time (less than 40 ns). In addition, these scintillators demonstrate good pulse shape discrimination capability. The grown pure crystals show strong luminescence and high light yields due to the presence of Tl ion in the host lattice. Thanks to the high Z‐number and density of the Tl, the grown scintillators have high density (ρ &gt; 4 g cm−3) and high effective Z‐number (Zeff ≥ 60). Being hygroscopic, like other halide scintillators, these single crystals are grown by the Bridgman technique. It is expected that the discovered scintillators will perform better than most commercial scintillators used in different applications. Significant improvement in the scintillation properties are achieved with the modification of the crystal growth procedure of the grown scintillators. Preliminary results revealed that these scintillators are very promising from an application point of view, while further investigations are underway for the enhancement of the present scintillators as well as for the discovery of new compounds of this family.

Microstructure evolution in two-step-sintering process toward transparent Ce:(Y,Gd)3(Ga,Al)5O12 scintillation ceramics

Scintillators are broadly utilized in high energy particle detection and medical imaging. Ce:(Y,Gd)3(Ga,Al)5O12 ceramics has recently demonstrated excellent scintillation properties and great commercialization potential. The controllable preparation technology for high quality transparent ceramics is urgently needed to promote the industrial production. In this work, using the co-precipitated nanopowder, we fabricated Ce:Gd2YGa3Al2O12 transparent ceramics by the two-step-sintering (pre-sintering followed by hot-isostatic-pressing). The microstructure evolution during sintering process reveals that the specific type of microstructure of pre-sintered ceramics with fine grains, high density and minimum number of residual intergranular pores is the key to achieve transparent ceramics by hot-isostatic-pressing. By controlling sintering process, the type and quantity of pores as well as grain size of ceramics can be tailored to meet the microstructure-controllable preparation of Ce:Gd2YGa3Al2O12 ceramics. The obtained Ce:Gd2YGa3Al2O12 ceramics show the good transmittance (62%@520 nm), high light yield (∼37,500 ph/MeV), fast scintillation decay (61 ns) and good X-ray imaging performance.

Bright and fast scintillations of an inorganic halide perovskite CsPbBr3 crystal at cryogenic temperatures

Highly efficient scintillation crystals with short decay times are indispensable for improving the performance of numerous detection and imaging instruments that use- X-rays, gamma-quanta, ionising particles or neutrons. Halide perovskites emerged recently as very promising materials for detection of ionising radiation that motivated further exploration of the materials. In this work, we report on excellent scintillation properties of CsPbBr3 crystals when cooled to cryogenic temperatures. The temperature dependence of luminescence spectra, decay kinetics and light yield under excitation with X-rays and α-particles was investigated. It is shown that the observed changes of spectral and kinetic characteristics of the crystal with temperature can be consistently explained by radiative decay of free excitons, bound and trapped excitons as well as electron-hole pairs originating from their disintegration. It has been found that the crystal exhibits a fast decay time constant of 1 ns at 7 K. The scintillation light yield of CsPbBr3 at 7 K is assessed to be 50,000 ± 10,000 ph/MeV at excitation with 12 keV X-rays and 109,000 ± 22,000 ph/MeV at excitation with α-particles of 241Am. This finding places CsPbBr3 in an excellent position for the development of a new generation of cryogenic, efficient scintillation detectors with nanosecond response time, marking a step-change in opportunities for scintillator-based applications.

Crystal growth and Ce3+ concentration optimization in Tl2LaCl5: An excellent scintillator for the radiation detection

High effective atomic number (70) and density (5.17 g/cm3) among the known halide scintillators with excellent scintillation performance make Tl2LaCl5 (TLC) a new potential candidate for X- and γ-ray detection. The preliminary scintillation performance of TLC was reported earlier for small crystal pieces without any detail information of synthesis, crystal growth optimization conditions and Ce3+ doping concentration, which are investigated in this study. The newly developed melt rotation technique was found to be the best one for the synthesis of TLC and probably for other Tl-based compounds among the known melting techniques. Pure and nominal Ce3+ concentration of 1%, 3%, 5%, 7% and 10% TLC crystals were grown with two zones vertical Bridgman technique in two different type of homemade furnaces and found the optimum thermal gradient, pulling and cooling rate as 25 °C/cm, 0.5 mm/h and 20 °C/h, respectively. The best energy resolution of ∼3.3% (FWHM) and light yield of ∼82,000 ph/MeV were obtained for TLC:3%Ce3+ under 662 keV γ-rays excitation. The promising scintillation performance of TLC revealed that this crystal could be used in Positron Emission Tomography (PET), environmental radiation monitoring and homeland security applications.

Results of the first NaI scintillating calorimeter prototypes by COSINUS

Over almost three decades the TAUP conference has seen a remarkable momentum gain in direct dark matter search. An important accelerator were first indications for a modulating signal rate in the DAMA/NaI experiment (today DAMA/LIBRA) reported in 1997. Today the presence of an annual modulation observed by DAMA, which matches in period and phase the expectation for dark matter, is doubtless and supported at > 9σ confidence. Despite the positive evidence from the DAMA experiment the underlying nature of dark matter is still considered an open and fundamental question of nowadays particle physics. No other direct dark matter search experiment could confirm the DAMA claim up to now; moreover, numerous null-results are in clear contradiction with DAMA under so-called standard assumptions for the dark matter halo and the interaction mechanism of dark with ordinary matter. As both bear a dependence on the target material, resolving this controversial situation will convincingly only be possible with an experiment using sodium iodide (NaI) as target, just like DAMA. COSINUS aims to even go a step further by combining NaI with a novel detection approach. DAMA and all other NaI experiments solely measure the scintillation light created by a particle interaction in the NaI crystal. COSINUS aims to operate NaI as a cryogenic calorimeter reading scintillation light and phonon/heat signal. Two distinct advantages arise from this approach, a substantially lower energy threshold for nuclear recoils and particle identification on an event-by-event basis. These key benefits will allow COSINUS to clarify a possible nuclear recoil origin of the DAMA signal with comparatively little exposure of O(100kg days) and, thereby, answer a long-standing question of particle physics. Today COSINUS is in R&D phase; in this contribution we show results from the 2nd prototype, albeit the first one of the final foreseen detector design. The key finding of this measurement is that pure, undoped NaI is a truly excellent scintillator at low temperatures: We measure 13.1% of the total deposited energy in the NaI crystal in the form of scintillation light (in the light detector).

Heat-resistant Pb(ii)-based X-ray scintillating metal-organic frameworks for sensitive dosage detection via an aggregation-induced luminescent chromophore.

The synergy of unusual X-aggregation induced luminescent chromophores and heavy Pb(ii) ions has facilitated excellent X-ray scintillation of two structurally similar Pb-SMOFs, which are heat-resistant due to solvent-free lattices. Owing to their higher Pb(ii) contents, Pb-SMOFs with larger X-ray absorption coefficients are more sensitive for X-ray dosage detection than powdered CsPbBr3.

X-ray excited ultralong room-temperature phosphorescence for organic afterglow scintillators.

We present X-ray-excitable organic ultralong room temperature phosphorescence (X-OURTP) for afterglow scintillators through implanting lone-pair electron involved n-π* transitions and efficient charge transfer characters into H-aggregations of organic crystals. The thus designed X-OURTP molecule exhibits ultralong lifetimes up to 790 ms, high phosphorescence quantum yields of ∼8%, and excellent scintillation stability. These findings will pave the way to the design of organic afterglow scintillators, simulating extensive investigations on the extraordinary X-OURTP.