Scintillation Light Research Articles

Congruent Glass Composite Scintillator for Efficient High-Energy Ray Detection.

The scintillator is the most crucial component in the high-energy ray detection system. The available scintillators suffer from the insurmountable drawbacks including poor shaping ability for single crystal and ceramic and low efficiency for glass. Here, a glass composite scintillator is proposed from a congruent crystallization system which possesses both excellent processability and high scintillating yield. It can be fabricated into diverse shapes and sizes including the bulk and tiny fiber. Benefitting from the unique compositing combination with a high crystallization ratio, the glass composite exhibits a giant scintillating light yield of ≈26,000 photons per MeV. The practical application for X-ray imaging is demonstrated and a high spatial resolution of 12 lpmm-1 is achieved. Furthermore, the fiber derived detector is built and the remote and micro-area detection is realized. These findings not only represent a novel design concept for the development of glass composite but also suggest a great step for expanding the scope of scintillators.

Improvement and Characterisation of the ArCLight Large-Area Dielectric Light Detector for Liquid-Argon Time Projection Chambers

The detection of scintillation light in noble-liquid detectors is necessary for identifying neutrino interaction candidates from beam, astrophysical, or solar sources. Large monolithic detectors typically have highly efficient light sensors, like photomultipliers, mounted outside their electric field. This option is not available for modular detectors that wish to maximize their active volume. The ArgonCube light readout system detectors (ArCLights) are large-area thin-wavelength-shifting (WLS) panels that can operate in highly proximate modular detectors and within the electric field. The WLS plastic forming the bulk structure of the ArCLight has Tetraphenyl Butadiene (TPB) and sheets of dichroic mirror layered across its surface. It is coupled to a set of six silicon photomultipliers (SiPMs). This publication compares TPB coating techniques for large surface areas and describes quality control methods for large-scale production.

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.

Scintillation light in SBND: simulation, reconstruction, and expected performance of the photon detection system

SBND is the near detector of the Short-Baseline Neutrino program at Fermilab. Its location near to the Booster Neutrino Beam source and relatively large mass will allow the study of neutrino interactions on argon with unprecedented statistics. This paper describes the expected performance of the SBND photon detection system, using a simulated sample of beam neutrinos and cosmogenic particles. Its design is a dual readout concept combining a system of 120 photomultiplier tubes, used for triggering, with a system of 192 X-ARAPUCA devices, located behind the anode wire planes. Furthermore, covering the cathode plane with highly-reflective panels coated with a wavelength-shifting compound recovers part of the light emitted towards the cathode, where no optical detectors exist. We show how this new design provides a high light yield and a more uniform detection efficiency, an excellent timing resolution and an independent 3D-position reconstruction using only the scintillation light. Finally, the whole reconstruction chain is applied to recover the temporal structure of the beam spill, which is resolved with a resolution on the order of nanoseconds.

Real-time measurement of two-dimensional LET distributions of proton beams using scintillators.


The linear energy transfer (LET) of proton therapy beams increases rapidly from the Bragg peak to the end of the beam. Although the LET can be determined using analytical or computational methods, a technique for efficiently measuring its spatial distribution has not yet been established. Thus, the purpose of this study is to develop a technique to measure the two-dimensional LET distribution in proton therapy in real time using a combination of multiple scintillators with different quenching. Inorganic and organic scintillator sheets were layered and irradiated with proton beams. Two-color signals of the CMOS sensor were obtained from the scintillation light and calibration curves were generated using LET. LET was calculated using Monte Carlo simulations as LETt and LETd weighted by fluence and dose, respectively. The accuracy of the calibration curve was evaluated by comparing the calculated and measured LET values for the 200 MeV monoenergetic and spread-out Bragg peak (SOBP) beams. LET distributions were obtained from the calibration curves.
Main results:
The deviation between the calculated and measured LET values was evaluated. For both LETt and LETd, the deviation in the plateau region of the monoenergetic and SOBP beams tended to be larger than those in the peak region. The deviation was smaller for LETd. In the obtained LETd distribution, the deviation between the calculated and measured values agreed within 3% in the peak region, while the deviation was larger in other regions. The LET distribution can be measured with a single irradiation using two scintillator sheets. This method may be effective for verifying LET in daily clinical practice and for quality control.&#xD.

Light response of poly(ethylene 2,6-naphthalate) to neutrons

There is an increasing necessity for low background active materials as ton-scale, rare-event and cryogenic detectors are developed. Poly(ethylene-2,6-naphthalate) (PEN) has been considered for these applications because of its robust structural characteristics, and its scintillation light in the blue wavelength region. Radioluminescent properties of PEN have been measured to aid in the evaluation of this material. In this article we present a measurement of PEN’s quenching factor using three different neutron sources; neutrons emitted from spontaneous fission in 252Cf , neutrons generated from a DD generator, and neutrons emitted from the 13C(α,n)16O and the 7Li(p,n)7Be nuclear reactions. The fission source used time-of-flight to determine the neutron energy, and the neutron energy from the nuclear reactions was defined using thin targets and reaction kinematics. The Birks’ factor and scintillation efficiency were found to be kB = 0.12 ± 0.01 mm MeV−1 and S = 1.31 ± 0.09 MeVeeMeV−1 from a simultaneous analysis of the data obtained from the three different sources. With these parameters, it is possible to evaluate PEN as a viable material for large-scale, low background physics experiments.

Measurement of muon flux behind the beam dump of the J-PARC Hadron Experimental Facility

A muon-flux measurement behind the beam dump of the J-PARC Hadron Experimental Facility was performed with a compact muon detector that can be inserted into a vertical observing hole with 81 mm in diameter which was dug underground. The detector consists of 12 plastic scintillation strips with a length of 80 mm each, which are arranged with cylindrical shape and contained inside an aluminum housing with an outer diameter of 75 mm. A silicon photomultiplier is coupled to the end of each strip to collect the scintillating light. The flux of the muons penetrating the beam dump was scanned vertically at intervals of 0.5 m, showing a wide distribution with a maximum at the beam level. The muon flux was consistent with the expectation from a Monte-Carlo simulation at more than 1 m away from the beam axis, which is expected to be used for signal-loss evaluation in the future KOTO II experiment for measuring rare kaon decays. The data can also be used in improving the accuracy of shielding calculations in the radiation protection.

Ca co-doped CsI(Tl) crystal scintillator for γ- and X-ray detecting applications

The vertical Bridgman method is used for the growth of single-doped CsI(Tl) and CsI(Tl:Ca) crystals, which has been evaluated for feasible applications in X-ray imaging and radiation detection. The powder XRD technique study reveals a single-crystalline phase of the grown crystal. The emission spectra show a broad emission band with a maximum of 540 nm under X-ray excitation, along with the characteristic emissions that arose from the Tl+ intra-center transition. The scintillation qualities of the grown crystal were studied via the pulse height spectra, scintillation light yield, energy resolution, and scintillation decay time. Pulse shape discrimination (PSD) was investigated under γ-rays and α-particles excitation sources. Moreover, the X-ray imaging application was investigated by an X-ray synchrotron at the Synchrotron Light Research Institute to study the performance of the grown crystal. These preliminary investigations suggest that the grown CsI(Tl:Ca) crystal can be one of the promising crystals for γ- and X-ray detecting applications.

Power over fiber development for HEP detectors

Power-over-Fiber (PoF) technology has been used extensively in settings where high voltages require isolation from ground and electromagnetic isolation is critical. In cryogenic environments, PoF offers a reliable power transmission technology, leveraging optical fibers to transfer power with minimal system degradation. PoF technology excels in maintaining low noise levels and isolation when delivering power to sensitive electronic systems operating in extreme temperature ranges and high voltage environments. In a novel application of PoF for a HEP detector, power is provided to photon detector modules located on a surface at ∼300 kV with respect to ground in the planned DUNE experiment. This summary paper of the PoF talk at the 16th PISA Meeting on Advanced Detectors highlights the R&D effort of PoF in extreme conditions and underscores its capacity to revolutionize power delivery and management in critical applications offering a dependable solution with low noise, optimal efficiency, and superior isolation. The DUNE (Abi et al., 2020) experiment will soon deploy large liquid argon (LAr) time projection chambers (TPC) to detect neutrino interactions and other particle physics phenomena. In addition to the particle tracking provided by the TPC, photon detectors, powered by a first ever PoF system, in the cryostat will leverage the high scintillation light yield of LAr to provide crucial timing and additional calorimetric information.

Developing MATLAB graphical user interface for acquiring single star SCIDAR data

To enhance operational efficiency and meet experimental demands, we have developed a graphical user interface (GUI) using MATLAB for Acquiring Single Star SCIDAR Data, leveraging the software’s integrated GUI Development Environment (GUIDE) tool. This interface streamlines the preprocessing and numerical computation of the power spectrum of atmospheric speckles while providing real-time graphical representations of atmospheric parameters, including the vertical profile of the refractive index structure function Cn2(h). It also incorporates parameters related to adaptive optics and high angular resolution, such as seeing, enabling immediate and instantaneous visual assessment of observational conditions. Furthermore, the novelty of this GUI lies in the ease of acquiring and processing data from various atmospheric parameters. The Single Star SCIDAR (Scintillation Detection and Ranging) method relies on analyzing the scintillation of light from single stars to assess the turbulent characteristics of the atmosphere. This assessment is based on the description provided by Cn2(h) derived from minimizing an objective function determined using the power spectrum of atmospheric speckles from single stars. For this purpose, a minimization algorithm called active-set is used.

Photoluminescence and scintillation properties of rare earth doped Lu2O3 single crystal grown by floating zone method

A series of Lu2O3 single crystals doped with rare earth (RE) ions (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, dopant concentrations are 1 %) was synthesized by the floating zone method. Their photoluminescence (PL) and scintillation properties were evaluated. In PL, emissions due to 4f-4f transitions of trivalent rare earth ions were observed, and those doped with Nd3+, Eu3+, Tb3+ and Er3+ showed the highest emission intensities among the samples. As a scintillation property, those doped with Eu, Gd, and Dy showed a clear photoabsorption peak under 137Cs 662 keV γ-ray irradiation. Among them, the Eu3+-doped Lu2O3 showed the highest scintillation light yield of 67000 photons/MeV. The current work conducted the first systematic study of rare earth doped Lu2O3 single crystals grown by the floating zone method.

Optimizing the spatial resolution and gamma discrimination of SiPM-based Anger cameras

SiPM Anger cameras have been designed for use as 2-dimensional thermal neutron detectors for scientific applications such as at single crystal diffraction instruments. These cameras utilize a neutron sensitive scintillator and an array of SiPM photosensors, separated by a light spreading glass. While this optics package is very effective at detecting and positioning neutrons, it is also sensitive to gamma rays, which are a source of unwanted noise. In this work, we underwent a search of scintillator and spreader glass thicknesses to determine the optimal combination for maximizing spatial resolution. Both experimental results and GEANT4 simulations are presented. To address the issue of gamma ray detection, we have also designed and presented a multi-layer scintillator that reduces the amount of scintillation light produced via gamma-ray energy deposition, allowing for easier pulse-height discrimination. A sample of this geometry has been produced that results in a factor of 2 improvement over an equivalent thickness monolithic scintillator.

Proportional scintillation in liquid xenon: demonstration in a single-phase liquid-only time projection chamber

The largest direct dark matter search experiments to date employ dual-phase time projection chambers (TPCs) with liquid noble gas targets. These detect both the primary photons generated by particle interactions in the liquid target, as well as proportional secondary scintillation light created by the ionization electrons in a strong electric field in the gas phase between the liquid-gas interface and the anode. In this work, we describe the detection of charge signals in a small-scale single-phase liquid-xenon-only TPC, that features the well-established TPC geometry with light readout above and below a cylindrical target. In the single-phase TPC, the proportional scintillation light (S2) is generated in liquid xenon in close proximity to 10 μm diameter anode wires. The detector was characterized and the proportional scintillation process was studied using the 32.1 keV and 9.4 keV signals from 83mKr decays. A charge gain factor g 2 of up to (1.9 ± 0.3) PE/electron was reached at an anode voltage 4.4 kV higher than the gate electrode 5 mm below it, corresponding to (29 ± 6) photons emitted per ionization electron. The duration of S2 signals is dominated by electron diffusion and approaches the xenon de-excitation timescale for very short electron drift times. The electron drift velocity and the longitudinal diffusion constant were measured at a drift field of 470 V/cm. The results agree with the literature and demonstrate that a single-phase TPC can be operated successfully.

A 3D photon-to-digital converter readout for low-power and large-area applications

A new trend in large area noble liquid experiments is to measure the scintillation light with photodetectors and their electronics inside the active volume. Compared to the typical approach of using silicon photomultipliers (SiPM) with an analog readout chain leading to an analog-to-digital converter, this paper presents a new 3D photon-to-digital converter (PDC) readout that takes advantage of the binary nature of the single-photon avalanche diodes (SPAD). The readout contains 4096 pixels over 25 mm2, each including a 3D bonding pad and a quenching circuit. The readout features three different outputs: a fast flag to get the timestamp of each event from an external time-to-digital converter, a digital sum to retrieve the number of pixels triggered during an event, and an analog monitor to generate an analog SiPM-like output. The analog monitor is also used to validate the two former digital outputs. The readout also includes 61 2D CMOS SPADs for validation purpose prior to the final 3D integration with SPADs custom made according to our design by Teledyne DALSA (Bromont, Canada). As a first system integration toward large-area detector applications, a mini-tile of 2 × 2 readouts has been developed to test all the functionalities. The measured single-photon timing resolution ranges from 72 to 93 ps FWHM across the mini-tile SPAD channels population (i.e. 4 × 61 channels). The flag timing resolution is below 95 ps RMS, which includes the contribution of the optimized flag H-tree but also an additional trigger tree that replaces the 3D SPAD array at this stage of development. Once bonded with the 3D SPADs, the trigger tree won't be required to measure the flag timing resolution. With the removed contribution of the trigger tree, the estimated flag timing resolution should be below 45 ps RMS. The extent of the benefits of the digital sum output depend on the application, and this paper focuses on two cases. First, a low-power coincidence scheme such as required by the nEXO liquid xenon experiment, leading to a power consumption as low as 140 μW per PDC. With a finer sampling of the scintillation light such as required for pulse shape discrimination in liquid argon, the power consumption remains below 100 μW per PDC. Overall, this readout is designed as a replacement for a typical analog SiPM chain, without compromise on the performances.

Luminescence and scintillation properties of TlCdCl3:Sb crystals

An ideal scintillator for X- and gamma-ray detection should have a high light yield and a high effective atomic number (Zeff). In this study, we developed undoped TlCdCl3 crystals and TlCdCl3:Sb (Sb: 0.5, 1.0 and 1.5 mol%) crystals with high Zeff (TlCdCl3:68.7), as candidate scintillators. The crystals were grown using the self-seeding solidification method, and their photoluminescence (PL) and scintillation properties were investigated. For the undoped TlCdCl3 crystals, emission peaks were observed at 460 nm and 485 nm in the PL and X-ray-induced radioluminescence (XRL) spectra, respectively. For the TlCdCl3:Sb crystals, the PL spectra showed emission peaks at 480, 480 and 500 nm, while the XRL spectra exhibited peaks at approximately 510 nm. The emission bands of the TlCdCl3:Sb crystals were shifted to longer wavelengths than those of the undoped TlCdCl3 crystals. The scintillation decay time constants for the undoped TlCdCl3 crystals were 51 and 2613 ns, whereas for the TlCdCl3:Sb crystals, they were in the range of 65–81 and 4550–7350 ns. These results suggest that the incorporation of Sb3+ ions induces long components of several thousand nanoseconds. The redshift and appearance of these long components indicate that Sb3+ ions act as new luminescence centers in the undoped TlCdCl3 crystal. The scintillation light yield of the TlCdCl3:Sb 1.0 mol% crystal was measured at 10,300 photons/MeV. The doping of Sb3+ ions into the TlCdCl3 lattice improved the scintillation light yield by up to four times compared to the undoped TlCdCl3 crystal.

Predicting time-of-flight with Cerenkov light in BGO: a three-stage network approach with multiple timing kernels prior

Objective.In the quest for enhanced image quality in positron emission tomography (PET) reconstruction, the introduction of time-of-flight (TOF) constraints in TOF-PET reconstruction offers superior signal-to-noise ratio. By employing BGO detectors capable of simultaneously emitting prompt Cerenkov light and scintillation light, this approach combines the high time resolution of prompt photons with the high energy resolution of scintillation light, thereby presenting a promising avenue for acquiring more precise TOF information.Approach.In Stage One, we train a raw method capable of predicting TOF information based on coincidence waveform pairs. In Stage Two, the data is categorized into 25 classes based on signal rise time, and the pre-trained raw method is utilized to obtain TOF kernels for each of the 25 classes, thereby generating prior knowledge. Within Stage Three, our proposed deep learning (DL) module, combined with a bias fine-tuning module, utilizes the kernel prior to provide bias compensation values for the data, thereby refining the first-stage outputs and obtaining more accurate TOF predictions.Main results.The three-stage network built upon the LED method resulted in improvements of 11.7 ps and 41.8 ps for full width at half maximum (FWHM) and full width at tenth maximum (FWTM), respectively. Optimal performance was achieved with FWHM of 128.2 ps and FWTM of 286.6 ps when CNN and Transformer were utilized in Stages One and Three, respectively. Further enhancements of 2.3 ps and 3.5 ps for FWHM and FWTM were attained through data augmentation methods.Significance.This study employs neural networks to compensate for the timing delays in mixed (Cerenkov and scintillation photons) signals, combining multiple timing kernels as prior knowledge with DL models. This integration yields optimal predictive performance, offering a superior solution for TOF-PET research utilizing Cerenkov signals.

Near Ultraviolet‐Excitable Cyan‐Emissive Hybrid Copper(I) Halides Nonlinear Optical Crystals with Near‐Unity Photoluminescence Quantum Yield and High‐Efficiency X‐ray Scintillation

AbstractDesigning and synthesizing multifunctional hybrid copper halides with near ultraviolet (NUV) light‐excited high‐energy emission (<500 nm) remains challenging. Here, a pair of broadband‐excited high‐energy emitting isomers, namely, α‐/β‐(MePh3P)2CuI3 (MePh3P=methyltriphenylphosphonium), were synthesized. α‐(MePh3P)2CuI3 with blue emission peaking at 475 nm is firstly discovered wherein its structure contains regular [CuI3]2− triangles and crystallizes in centrosymmetric space group P21/c. While β‐(MePh3P)2CuI3 featuring distorted [CuI3]2− planar triangles shows inversion symmetry breaking and crystallizes in the noncentrosymmetric space group P21, which exhibits cyan emission peaking at 495 nm with prominent near‐unity photoluminescence quantum yield and the excitation band ranging from 200 to 450 nm. Intriguingly, β‐(MePh3P)2CuI3 exhibits phase‐matchable second‐harmonic generation response of 0.54×KDP and a suitable birefringence of 0.06@1064 nm. Furthermore, β‐(MePh3P)2CuI3 also can be excited by X‐ray radioluminescence with a high scintillation light yield of 16193 photon/MeV and an ultra‐low detection limit of 47.97 nGy/s, which is only 0.87 % of the standard medical diagnosis (5.5 μGy/s). This work not only promotes the development of solid‐state lighting, laser frequency conversion and X‐ray imaging, but also provides a reference for constructing multifunctional hybrid metal halides.

Imaging systems for the liquid Argon target of SAND at the DUNE Near Detector Complex

The Deep Underground Neutrino Experiment (DUNE) has among its primary goals the determination of the neutrino mass ordering and the possible CP-violating phase in the neutrino mixing matrix. The System for On-Axis Neutrino Detection (SAND) is one of the three components of the DUNE Near Detector complex, permanently located on-axis to monitor the neutrino beam stability and measure its flux. SAND includes a novel liquid Argon detector - GRAIN - designed to image neutrino interactions using scintillation light produced in Ar by charged particles, eliminating the dependence on slow charge collection of LAr TPCs. Two optical systems are currently being developed for GRAIN, both based on Silicon Photomultiplier (SiPM) matrices, coupled either to UV cryogenic lenses or Coded Aperture masks. This contribution will present the design of GRAIN optical systems and their spatial resolution performance in preliminary simulation studies.

Performance stability of plastics for neutron-gamma pulse shape discrimination

The introduction of the first commercially available plastic scintillators with pulse shape discrimination (PSD) offered by Eljen Technology marked progress towards potentially replacing liquid scintillators in neutron detection. However, use of these plastics over several recent years has revealed an important flaw in these materials: the eventual degradation of scintillation light output and PSD performance. Studies described in this paper considered possible reasons for this degradation. Experiments conducted with numerous lab-prepared and commercial EJ-276 samples showed that the main factor affecting the instability is oxidation that involves highly reactive radicals generated during the polymerization process or from the further breakdown of polymer chains under oxygen/air exposure. Based on the obtained results, the stability of scintillation performance for PPO (2,5-Diphenyloxazole)-based PSD plastics has been improved through modifications of the composition via the utilization of scintillation dyes and compounds with antioxidant properties that diminish the effects of oxidation. Elements of these studies were used in the commercial production of the most recent EJ-276D PSD plastic version for fast neutron detection and 6Li-loaded plastics for thermal neutron and antineutrino detection applications. Performance projections of the new PSD plastics indicate a likely degradation of less than 10 % over 5–10 years in comparison to previous EJ-276 that might lose up to 30–40 % of the scintillation light during 1–2 years of storage or deployment under ambient conditions.

Solution Synthesis and Light-Emitting Applications of One-Dimensional Lead-Free Cerium(III) Metal Halides.

Combining rare earth elements with the halide perovskite structure offers valuable insights into designing nonlead (Pb) luminescent materials. However, most of these compositions tend to form zero-dimensional (0D) networks of metal-halide polyhedra, with higher-dimensional (1D, 2D, and 3D) structures receiving relatively less exploration. Herein, we present synthesis and optical properties of Cs3CeCl6·3H2O, characterized by its unique 1D crystal structure. The conduction band minimum of Cs3CeCl6·3H2O becomes less localized as a result of the increased structural dimension, making it possible for the materials to achieve an efficient electrical injection. For both Cs3CeCl6·3H2O single crystals and nanocrystals, we also observed remarkable luminescence with near-unity photoluminescence quantum yield and exceptional phase stability. Cs3CeCl6·3H2O single crystals demonstrate an X-ray scintillation light yield of 31900 photons/MeV, higher than that of commercial LuAG:Ce (22000 photons/MeV); electrically driven light-emitting diodes fabricated with Cs3CeCl6·3H2O nanocrystals yield the characteristic emission of Ce3+, indicating their potential use in next-generation violet-light-emitting devices.