Scintillation Emission Research Articles

Optimized Scintillation Imaging in low dose rate and bright room light conditions.

To develop a robust method for non-contact surface dosimetry during Total Body Irradiation (TBI) that uses an optimally paired choice of scintillator material with camera photocathode and can work insensitively to the normal ambient room lighting conditions (~500 Lux). 
Approach: This goal was approached by assessing the emission contrast of scintillator signal to background room ratio (SBR) detected by the camera, in the challening conditions of low dose rate TBI with high room lights. A total of 9 fast-response scintillators, 3 wavelength shifters, and 2 camera photocathodes were systematically tested to determine the optimal combination. The effects of room lights on the scintillator signal and the background signal were assessed to avoid signal saturation while retaining accurate dose measurement. A bandpass wavelength filter was then applied to reduce the effects on room lights and scintillator signal.
Main Results: One scintillator (EJ262) combined with a blue-green sensitive photocathode camera and a 500nm band pass filter produced the greatest available scintillator SBR of 95 with maximal room lights on. The caveat is that this design rejects all patient Cherenkov light, which can be useful for visualizing the patient treatment. Another option which retained the Cherenkov signal but produced less available scintillator signal was found with another scintillator (EJ-260) and a red photocathode camera with SBR of 35, but a narrow bandpass filter is required to make it work in ambient room lights, which addition will also remove most of the Cherenkov signal. 
Significance: Non-contact scintillator imaging can be used for surface dosimetry in TBI with appropriate pairing of scintillator emission spectrum and camera photocathode sensitivity or optical filtering range.&#xD.

Analyze Methodology of ToF Spectrum on Cherenkov and Scintillation Emission in BGO Scintillator

Analyze Methodology of ToF Spectrum on Cherenkov and Scintillation Emission in BGO Scintillator

Purcell-enhanced x-ray scintillation.

Scintillation materials convert high-energy radiation to optical light through a complex multistage process. The last stage of the process is spontaneous light emission, which usually governs and limits the scintillator emission rate and light yield. For decades, scintillator research focused on developing faster-emitting materials or external photonic coatings for improving light yields. Here, we experimentally demonstrate a fundamentally different approach: enhancing the scintillation rate and yield via the Purcell effect, utilizing optical environment engineering to boost spontaneous emission. This enhancement is universally applicable to any scintillating material and dopant when the material's nanoscale geometry is engineered. We design a thin multilayer nanophotonic scintillator, demonstrating Purcell-enhanced scintillation with 50% enhancement in emission rate and 80% enhancement in light yield. The emission is robust to fabrication disorder, further highlighting its potential for x-ray applications. Our results show prospects for bridging nanophotonics and scintillator science toward reduced radiation dosage and increased resolution for high-energy particle detection.

Indirect detector for ultra-high-speed X-ray micro-imaging with increased sensitivity to near-ultraviolet scintillator emission.

Ultra-high-speed synchrotron-based hard X-ray (i.e. above 10 keV) imaging is gaining a growing interest in a number of scientific domains for tracking non-repeatable dynamic phenomena at spatio-temporal microscales. This work describes an optimized indirect X-ray imaging microscope designed to achieve high performance at micrometre pixel size and megahertz acquisition speed. The entire detector optical arrangement has an improved sensitivity within the near-ultraviolet (NUV) part of the emitted spectrum (i.e. 310-430 nm wavelength). When combined with a single-crystal fast-decay scintillator, such as LYSO:Ce (Lu2-xYxSiO5:Ce), it exploits the potential of the NUV light-emitting scintillators. The indirect arrangement of the detector makes it suitable for high-dose applications that require high-energy illumination. This allows for synchrotron single-bunch hard X-ray imaging to be performed with improved true spatial resolution, as herein exemplified through pulsed wire explosion and superheated near-nozzle gasoline injection experiments at a pixel size of 3.2 µm, acquisition rates up to 1.4 MHz and effective exposure time down to 60 ps.

Novel method to study saturation of silicon photomultiplier in scintillation detector

Signal saturation in the Silicon PhotoMultiplier (SiPM) often causes a serious problem in using a detector equipped with SiPMs for scintillator readout. Conventionally, SiPM signal saturation is measured through direct injection of visible light pulses to the SiPM. However, the method works poorly with the scintillation detector because the effects of the time constant of the emission of scintillation light are not included. Here, we present a novel method to measure the precise degree of SiPM signal saturation in scintillation detectors. The key difference from the conventional method is to use UV light pulses, as opposed to visible light ones, to inject and excite scintillation light in the detector. It allows us to directly measure the degree of saturation in situ taking into account all the major effects in the detector, such as the time constant of the scintillation emission. We also develop a new model for SiPM signal saturation and validate it with the measured degree of saturation with the above-mentioned new method.

Size-Dependent Blue Emission from Europium-Doped Strontium Fluoride Nanoscintillators for X-Ray-Activated Photodynamic Therapy.

Successful implementation of X-ray-activated photodynamic therapy (X-PDT) is challenging because most photosensitizers (PSs) absorb light in the blue region, but few nanoscintillators produce efficient blue scintillation. Here, efficient blue-emitting SrF2:Eu scintillating nanoparticles (ScNPs) are developed. The optimized synthesis conditions result in cubic nanoparticles with ≈32nm diameter and blue emission at 416nm. Coating them with the meso-tetra(n-methyl-4-pyridyl) porphyrin (TMPyP) in a core-shell structure (SrF@TMPyP) results in maximum singlet oxygen (1O2) generation upon X-ray irradiation for nanoparticles with 6TMPyP depositions (SrF@6TMPyP). The 1O2 generation is directly proportional to the dose, does not vary in the low-energy X-ray range (48-160 kVp), but is 21% higher when irradiated with low-energy X-rays than irradiations with higher energy gamma rays. In the clonogenic assay, cancer cells treated with SrF@6TMPyP and exposed to X-rays present a significantly reduced survival fraction compared to the controls. The SrF2:Eu ScNPs and their conjugates stand out as tunable nanoplatforms for X-PDT due to the efficient blue emission from the SrF2:Eu cores; the ability to adjust the scintillation emission in terms of color and intensity by controlling the nanoparticle size; the efficient 1O2 production when conjugated to a PS and the efficacy of killing cancer cells.

Toward "super-scintillation" with nanomaterials and nanophotonics.

Following the discovery of X-rays, scintillators are commonly used as high-energy radiation sensors in diagnostic medical imaging, high-energy physics, astrophysics, environmental radiation monitoring, and security inspections. Conventional scintillators face intrinsic limitations including a low extraction efficiency of scintillated light and a low emission rate, leading to efficiencies that are less than 10 % for commercial scintillators. Overcoming these limitations will require new materials including scintillating nanomaterials ("nanoscintillators"), as well as new photonic approaches that increase the efficiency of the scintillation process, increase the emission rate of materials, and control the directivity of the scintillated light. In this perspective, we describe emerging nanoscintillating materials and three nanophotonic platforms: (i) plasmonic nanoresonators, (ii) photonic crystals, and (iii) high-Q metasurfaces that could enable high performance scintillators. We further discuss how a combination of nanoscintillators and photonic structures can yield a "super scintillator" enabling ultimate spatio-temporal resolution while enabling a significant boost in the extracted scintillation emission.

Characterization of the scintillation response of water-based liquid scintillator to alpha particles, and implications for particle identification

Next-generation large-scale neutrino detectors, from Eos, at the 1 t scale, to Theia, at the 10 s-of-kt scale, will utilize differences in both the scintillation and Cherenkov light emission for different particle species to perform background rejection. This manuscript presents measurements of the scintillation light yield and emission time profile of water-based liquid scintillator samples in response to α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} radiation. These measurements are used as input to simulation models used to make predictions for future detectors. In particular, we present the timing-based particle identification achievable in generic water-based scintillator detectors at the 4 t, 1 kt, and 100 kt scales. We find that α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}/β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta $$\\end{document} discrimination improves with increasing scintillation concentration and we identify better than 80% α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} rejection for 90% β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta $$\\end{document} acceptance in 10% water-based liquid scintillator, at the 4 t scale.

Radiation response properties of Ce-doped CaF2 transparent ceramics

We report on the luminescence properties of CaF2 transparent ceramics having various concentrations of CeF3 (0.1 %, 0.5 %, and 1 %). Scintillation emissions centered at approximately 318, 345, and 386 nm derived from the 5d→4f transition of Ce3+ were detected, and scintillation light yields were determined to be 8600 photons/MeV (0.1 % CeF3), 1930 photons/MeV (0.5 % CeF3), and 1850 photons/MeV (1 % CeF3) under gamma-ray irradiation from 241Am. The Ce-doped CaF2 transparent ceramics showed thermally stimulated luminescence (TSL) with a broad glow peak at around 115–145 °C, and their dose response curves were determined over a broad dose range (0.01–3 mGy). Moreover, optically stimulated luminescence (OSL) exponential decay curves were obtained under 500 nm stimulation light, and dose response curves were obtained in the dose range of 0.1–100 mGy. The minimum detectable dose was estimated to be 0.1 mGy. A direct correlation between scintillation light yields under gamma-ray irradiation and TSL/OSL intensities was demonstrated.

Improvement of X-ray excited luminescence properties of Mg4Ta2O9 scintillators by rare-earth doping

Hexagonal-structure Mg4Ta2O9 (MTO) powders doped by 0.25 at% RE (RE = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3 +, Yb3+, Lu3+, Y3+, Sc3+) were synthesized. All the rare earth-doped samples were checked by X-ray diffraction (XRD) and confirmed to be monophasic powders. Among them, Mg4Ta2O9 doped by 0.25 at% Gd3+ and Sc3+ had higher X-ray excited luminescence (XEL) emission peak intensities, 3.05 and 2.79 times of MTO, respectively. The optimal concentrations of Gd3+ and Sc3+ were investigated based on XEL main emission peak intensity changing with the amount of dopants in the range of 0∼1.0 at%. The optimal XEL emission peak intensities were measured 3.32 and 3.09 times of MTO for MTO: 0.8 at% Gd3+ and MTO: 0.4 at% Sc3+, respectively. The photoluminescence (PL) emission peaks at around 370 nm correspond to two excitation peaks at 158 and 215 nm. The excitation peak at 158 nm is about 10 times more than that of at 215 nm in intensity. The emission spectra excited by vacuum ultraviolet light at 158 nm and ultraviolet light at 215 nm were investigated associated with scintillation emission mechanism. MTO: 0.8 at% Gd3+ and MTO: 0.4 at% Sc3+ show potential application in security inspection, industrial detection, etc.

Discrimination of Fast and Thermal Neutrons Using a Novel Phoswich Detector of LaCl3 and LiI:Eu Single Crystal Scintillators

A novel phoswich detector was setup by employing LaCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> + LiI:Eu single crystal scintillators and was characterized in details for its performance with Am-Be, D-D and D-T neutron sources. LaCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> crystal shows transparency to the scintillation emission of LiI:Eu for light collection to PMT. Thermal and fast neutrons were successfully discriminated by pulse shape discrimination (PSD) with high value of figure of merit of 5.5 due to significant difference of their scintillation kinetics.

Near-Infrared Emitting of Zero-Dimensional Europium(II) Halide Scintillators: Energy Transfer Engineering via Sm2+ Doping

Near-infrared (NIR)-emitting scintillators, coupled with high quantum efficiency silicon-based photodetectors, have emerged as a promising solution for highly efficient radiation detection applications. However, the study of efficient NIR-emitting scintillators and their associated luminescence mechanism is still limited. In this work, we developed NIR-emitting zero-dimensional Cs4EuBr6 halide scintillators via Sm2+ doping. Single crystals of Cs4EuBr6 with varying Sm2+ concentrations were grown by the vertical Bridgman method. Under X-ray irradiation, the scintillation emission of highly Sm-doped Cs4EuBr6 single crystals is dominated by the Sm2+ 5d–4f emission peaking at 831 nm with a weak Eu2+ 5d–4f emission peaking at 443 nm. The energy transfer processes between Eu2+ and Sm2+ were investigated by using photoluminescence (PL) spectra, PL decay kinetics, and soft X-ray excited decay kinetics measurements. Based on the temperature-dependent PL decay results, we constructed a configurational coordinate diagram of Sm2+ in the Cs4EuBr6 host. Furthermore, we evaluated the gamma spectroscopy response of Cs4EuBr6:Sm single crystals using an avalanche photodiode detector known for its high sensitivity in the NIR wavelength region.

Lattice Expansion in Rb-Doped Hybrid Organic-Inorganic Perovskite Crystals Resulting in Smaller Band-Gap and Higher Light-Yield Scintillators.

Two-dimensional hybrid-organic-inorganic perovskite (2D-HOIP) lead bromide perovskite crystals have demonstrated great potential as scintillators with high light yields and fast decay times while also being low cost with solution-processable materials for wide energy radiation detection. Ion doping has been also shown to be a very promising avenue for improvements of the scintillation properties of 2D-HOIP crystals. In this paper, we discuss the effect of rubidium (Rb) doping on two previously reported 2D-HOIP single crystals, BA2PbBr4 and PEA2PbBr4. We observe that doping the perovskite crystals with Rb ions leads to an expansion of the crystal lattices of the materials, which also leads to narrowing of band gaps down to 84% of the pure compounds. Rb doping of BA2PbBr4 and PEA2PbBr4 shows a broadening in the photoluminescence and scintillation emissions of both perovskite crystals. Rb doping also leads to faster γ-ray scintillation decay times, as fast as 4.4 ns, with average decay time decreases of 15% and 8% for Rb-doped BA2PbBr4 and PEA2PbBr4, respectively, compared to those of undoped crystals. The inclusion of Rb ions also leads to a slightly longer afterglow, with residual scintillation still being below 1% after 5 s at 10 K, for both undoped and Rb-doped perovskite crystals. The light yield of both perovskites is significantly increased by Rb doping with improvements of 58% and 25% for BA2PbBr4 and PEA2PbBr4, respectively. This work shows that Rb doping leads to a significant enhancement of the 2D-HOIP crystal performance, which is of particular significance for high light yield and fast timing applications, such as photon counting or positron emission tomography.

Reconstruction algorithm for a novel Cherenkov scintillation detector

For future MeV-scale neutrino experiments, a Cherenkov scintillation detector, CSD, is of particular interest for its capability to reconstruct both energy and direction for charged particles. A type of new target material, slow liquid scintillator, SlowLS, which can be used to separate Cherenkov and scintillation lights, is one of the options for the neutrino detectors. A multi-hundred ton spherical CSD is simulated using a Geant4-based Monte Carlo software, which handles the detailed the micro processes of MeV particles and optical photons and the functions for photomultiplier, PMT, and readout electronics. Twelve SlowLS samples are simulated and studied to cover a wide range of scintillation light yields and scintillation emission time constants. Based on the detailed knowledge of the signal processes, simplified functions are constructed to predict the charge and time signals on the PMTs to fulfill an efficient reconstruction for the energy, direction, and position of charged particles. The performance of the SlowLS reconstruction, including the resulting energy, angular, and position resolution, and particle identification capability, is presented for these samples. The dependence of the performance on the scintillation light yield and emission time constants is understood. This study will be a guideline for future MeV-scale neutrino CSD design and SlowLS development for the interested physics goals.

Enhancing Large-Area Scintillator Detection with Photonic Crystal Cavities

Scintillators are materials that emit visible photons when bombarded by high-energy particles (X-ray, γ-ray, electrons, neutrinos, etc.) and are crucial for applications, including X-ray imaging and high-energy particle detection. Here, we show that one-dimensional (1D) photonic crystal (PhC) cavities, added externally to scintillator materials, can be used to tailor the intrinsic emission spectrum of scintillators via the Purcell effect. The emission spectral peaks can be shifted, narrowed, or split, improving the overlap between the scintillator emission spectrum and the quantum efficiency (QE) spectrum of the photodetector. As a result, the overall photodetector signal can be enhanced by over 200%. The use of external PhC cavities especially benefits thick and large-area scintillators, which are needed to stop particles with ultrahigh energy, as in large-area neutrino detectors. Our findings should pave the way to greater versatility and efficiency in the design of scintillators for applications, including X-ray imaging and positron emission tomography.

Investigating the effect of depth of interaction on coincidence time resolution

Abstract The timing properties of scintillator-based detectors are a matter of importance in a wide range of fields. As fast scintillators progress and the sensors that preserve the quantized nature of the luminescent signal evolve, the optical transfer time may not always be negligible in ultra-fast time measurement. The present paper discusses the implications of this in a specific configuration for ultra-fast time measurement. To this end, we consider factors influencing the time spread such as the distribution of depth of interaction, non-instantaneous scintillation emission mechanism, and optical transport kinetics. Although such a topic has previously been studied by researchers, the aim of this work is focused on analyzing the detailed factors that govern arrival time spread. From these factors, we are able to obtain the post-interaction time spread, and we then derived the optical transfer time spread (OTTS) by a weighted sum of post-interaction time spread based on the cumulative density function of the depth of interaction. Based on the rejection sampling method, we could obtain the set of arrival times by the OTTS, and then the coincidence time resolution of radioactive sources was calculated. Consequently, we found that the difference in the attenuation coefficient causes the difference in the arrival time distribution, but it does not lend a significant contribution to the coincidence time resolution. In addition, when radiation with different energies is incident, the emission mechanism has a dominant effect on the time resolution, and thus incident radiation having higher energy in the same detector system has a higher light yield, which can exhibit better timing resolution compared to radiation with relatively low energy.

FABRICATION A NEW FILM SCINTILLATOR BASED ON (8-HYDROXYQINOLATE) LITHIUM

Thin luminescent films of the organometallic complex of lithium 8-hydroxyquinolate (Liq) on glass substrates were fabricated by capillary deposition and lithography. A study of the spectral-luminescent properties of the obtained film structures was carried out. The analysis of the surface of the films was carried out. The light yield and the kinetics of scintillation emission of the obtained film structures are estimated.

Radiation Damage in Polyethylene Naphthalate Thin-Film Scintillators.

This paper describes the scintillation features and the radiation damage in polyethylene naphthalate 100 µm-thick scintillators irradiated with an 11 MeV proton beam and with a 1 MeV electron beam at doses up to 15 and 85 Mrad, respectively. The scintillator emission spectrum, optical transmission, light yield loss, and scintillation pulse decay times were investigated before and after the irradiation. A deep blue emission spectrum peaked at 422 nm, and fast and slow scintillation decay time constants of the order of 1–2 ns and 25–30 nm, respectively, were measured. After irradiation, transmittance showed a loss of transparency for wavelengths between 380 and 420 nm, and a light yield reduction of ~40% was measured at the maximum dose of 85 Mrad.

Heavily cerium-doped (Gd,La)AlO3 ceramic scintillators: Material optimization study

Cerium-doped aluminates with a perovskite structure are studied for their prospective material properties aiming at their application in scintillation detectors. These materials exhibit high density, and thermal and chemical stability and thanks to the allowed 5d-4f transition of Ce3+ also high scintillation emission intensity and fast decay can be obtained. Commercially successful perovskite scintillator is the cerium-doped yttrium aluminium perovskite (YAlO3:Ce) produced in single crystal form by the Czochralski method. To overcome its disadvantage of low density and effective atomic number the single crystal of gadolinium aluminium perovskite doped with cerium (GdAlO3:Ce) was studied, but has shown significantly lower light. This work pursues a new approach to improve the scintillation properties of this material. Ceramic pellets of gadolinium aluminium perovskite doped with cerium and admixed with lanthanum ((Gd,La)AlO3:Ce) were prepared using co-precipitation method. The effect of cerium and lanthanum content was studied using the radioluminescence and luminescence spectroscopy. An improvement of scintillation properties (emission intensity and decay kinetics), in comparison to GdAlO3:Ce reported so far, was achieved.

Design Principles of Hybrid Nanomaterials for Radiotherapy Enhanced by Photodynamic Therapy.

Radiation (RT) remains the most frequently used treatment against cancer. The main limitation of RT is its lack of specificity for cancer tissues and the limited maximum radiation dose that can be safely delivered without damaging the surrounding healthy tissues. A step forward in the development of better RT is achieved by coupling it with other treatments, such as photodynamic therapy (PDT). PDT is an anti-cancer therapy that relies on the light activation of non-toxic molecules—called photosensitizers—to generate ROS such as singlet oxygen. By conjugating photosensitizers to dense nanoscintillators in hybrid architectures, the PDT could be activated during RT, leading to cell death through an additional pathway with respect to the one activated by RT alone. Therefore, combining RT and PDT can lead to a synergistic enhancement of the overall efficacy of RT. However, the involvement of hybrids in combination with ionizing radiation is not trivial: the comprehension of the relationship among RT, scintillation emission of the nanoscintillator, and therapeutic effects of the locally excited photosensitizers is desirable to optimize the design of the hybrid nanoparticles for improved effects in radio-oncology. Here, we discuss the working principles of the PDT-activated RT methods, pointing out the guidelines for the development of effective coadjutants to be tested in clinics.