Scintillation Time Profile Research Articles

Development of a bi-solvent liquid scintillator with slow light emission

One of the most promising approaches for the next generation of neutrino experiments is the realization of large hybrid Cherenkov/scintillation detectors made possible by recent innovations in photodetection technology and liquid scintillator chemistry. The development of a potentially suitable future detector liquid with particularly slow light emission is discussed in the present publication. This cocktail is compared with respect to its fundamental characteristics (scintillation efficiency, transparency, and time profile of light emission) with liquid scintillators currently used in large-scale neutrino detectors. In addition, the optimization of the admixture of wavelength shifters for a scintillator with particularly high light emission is presented. Furthermore, the pulse-shape discrimination capabilities of the novel medium was studied using a pulsed particle accelerator driven neutron source. Beyond that, purification methods based on column chromatography and fractional vacuum distillation for the co-solvent DIN (Diisopropylnaphthalene) are discussed.

Linear energy transfer dependence of scintillation properties of CeF3

To elucidate the linear energy transfer (LET) effects on the scintillation properties of a self-activated scintillator, CeF3, from an aspect of excited state dynamics, we observed the scintillation time profiles of CeF3 under irradiations of pulsed beams having different LETs. The initial decay was faster for higher LET, which in line with the LET dependence observed for other self-activated scintillators in previous studies. The faster decay at higher LET can be explained in terms of competition between the scintillation caused by 5d–4f transition of Ce3+ ions and quenching owing to the interaction between excited Ce3+ ions close to each other.

Assessment of the scintillation properties of MgGa2O4 and ZnGa2O4 single crystals

We present the basic scintillation properties of MgGa2O4 and ZnGa2O4 crystals grown at Leibniz-Institut für Kristallzüchtung by the Czochralski and the Vertical Gradient Freeze methods, respectively. We prove that these two Ga-based spinels do scintillate under gamma irradiation, currently displaying scintillation yields up to about 2500 ph/MeV. We also show the scintillation time profiles and their anticorrelation with the scintillation yields (the lower the yield, the faster the scintillation decay). Finally, we indicate that radioluminescence of both MgGa2O4 and ZnGa2O4 is much more efficient at low temperatures, which suggests the presence of a strong thermal quenching decreasing their yield towards room temperature.

Scintillation properties of (Ga[formula omitted]Al[formula omitted])[formula omitted]O[formula omitted] ceramics

In this communication scintillation properties of (GaxAl1−x)2O3 (x = 1, 0.75, 0.5, and 0.2) ceramics are reported. The investigated samples have been fabricated through two-step spark plasma sintering. Their properties have been studied by means of pulse height spectra, scintillation time profiles, radio- and thermoluminescence. Although room temperature scintillation yields of the samples do not exceed 1000 ph/MeV, their scintillation decays appear relatively fast as compared to single crystals.

Impact of xenon doping in the scintillation light in a large liquid-argon TPC

The use of xenon-doped liquid argon (Xe-doped LAr) is a promising alternative for large-scale liquid argon Time Projection Chambers (LAr-TPC), since it mitigates the light suppression due to impurities and it also improves the photon-detection efficiency and uniformity with the distance. This study analyses the impact of using Xe-doped LAr in ProtoDUNE Dual-Phase, a 750 ton Dual-Phase LAr-TPC placed at CERN. ProtoDUNE Dual-Phase completed a Xe-doping data-taking campaign in summer 2020 by re-filling the detector with 230 tons of Xe-doped LAr contaminated with nitrogen, and performing dedicated nitrogen injections. The effects of the presence of Xe at 5.8 ppm in the scintillation light production and propagation are analysed in this paper, showing an increase of the collected photons, but a suppression of the light signal amplitude. A 60% increase of the light attenuation length is measured. The impact on the scintillation time profile is also studied. A model to fit the time profile is proposed and the time constants of the physics processes are obtained.

Heading for brighter and faster β-Ga2O3 scintillator crystals

Czochralski-grown β-Ga2O3 and β-Ga2O3:Si crystals with the free electron concentrations between 2.5·1016 and 4.3·1018 cm−3 have been characterized by means of pulse height and scintillation time profile measurements in order to assess their basic scintillation properties. At room temperature, with increasing free electron concentration in the studied range, the scintillation yields decrease from 8920 to 1930 ph/MeV, while the mean scintillation decay times pare down from 989 to 61 ns. However, when the brightest β-Ga2O3 sample is cooled down below 100 K, its scintillation yield exceeds 20000 ph/MeV.

Characterization of water-based liquid scintillator for Cherenkov and scintillation separation

This paper presents measurements of the scintillation light yield and time profile for a number of concentrations of water-based liquid scintillator, formulated from linear alkylbenzene (LAB) and 2,5-diphenyloxazole (PPO). We find that the scintillation light yield is linear with the concentration of liquid scintillator in water between 1 and 10% with a slope of 127.9pm 17.0 ph/MeV/concentration and an intercept value of 108.3pm 51.0 ph/MeV, the latter being illustrative of non-linearities with concentration at values less than 1%. This is larger than expected from a simple extrapolation of the pure liquid scintillator light yield. The measured time profiles are consistently faster than that of pure liquid scintillator, with rise times less than 250 ps and prompt decay constants in the range of 2.1–2.85 ns. Additionally, the separation between Cherenkov and scintillation light is quantified using cosmic muons in the CHESS experiment for each formulation, demonstrating an improvement in separation at the centimeter scale. Finally, we briefly discuss the prospects for large-scale detectors.

Semiconductor scintillator development: Pure and doped β-Ga2O3

Our recent research on scintillation properties of β-Ga2O3 crystals, either pure or singly-, doubly-, and triply-doped, obtained with the Czochralski method at the Leibniz-Institut für Kristallzüchtung, is summarized. The results of pulse height, scintillation time profile, and low temperature thermoluminescence measurements are analyzed, mostly in reference to the values of free electron concentration in the samples. Some correlations between particular parameters are found and discussed in order to give hints for a further development of the material.

Simulation of the argon response and light detection in a dual-phase TPC

G4DS is the GEANT4-based Monte Carlo simulation for the DarkSide program, tuned on the data of the DarkSide-50 experiment. It includes: a tuned optical model, for the description of the detector non uniformities at the percent-level; the accurate simulation of the scintillation time profile, used for pulse shape discrimination; an effective model for the ionization and scintillation mechanism in liquid argon. This tool, combined with the additional data from dedicated calibration experiment, provides a comprehensive model to describe the response of liquid argon in dual-phase TPCs. This document reviews the calibration procedure and discuss some application for for the DarkSide experiments.

Tailoring the scintillation properties of β-Ga2O3 by doping with Ce and codoping with Si

Measurements of pulse height spectra and scintillation time profiles performed on Czochralski-grown β-Ga2O3, β-Ga2O3:Ce, and β-Ga2O3:Ce,Si crystals are reported. The highest value of scintillation yield, 7040 ph/MeV, was achieved for pure β-Ga2O3 at a low free electron concentration, nevertheless Ce-doped crystals could also approach high values thereof. Si-codoping, however, decreases the scintillation yield. The presence of Ce, and the more of Ce and Si, in β-Ga2O3 significantly increases the contribution of the fastest components in scintillation time profiles, which makes β-Ga2O3 a very fast scintillator under γ-excitation.

β-Ga2O3:Ce as a fast scintillator: An unclear role of cerium

β-Ga2O3 and β-Ga2O3:Ce crystals have been grown by the Czochralski method and their scintillation properties have been studied by means of pulse height, radioluminescence and scintillation time profile measurements. It is shown that although the scintillation of β-Ga2O3:Ce is related to intrinsic excitonic emission, the doping with Ce improves some characteristics of the material. The prominent samples of β-Ga2O3:Ce display fast 6 ns (40%) scintillation, with total light yields of about 5000 ph/MeV.

Scintillation properties and effect of thermal annealing in Lu3Al5O12:Ce and Lu3Al5O12:Pr ceramics

The impact of thermal annealing on the properties of LuAG:Ce and LuAG:Pr ceramics has been investigated. The results of measurements of pulse height spectra, scintillation time profiles, absorption spectra, radioluminescence as a function of temperature, absorption spectra, as well as low temperature thermally stimulated luminescence, performed before and after annealing of the samples in air, are compared. Pulse height spectra are used to estimate the light outputs of the samples, while scintillation time profiles to find the decay time constants. Absorption spectra are analyzed to identify the observed lines and/or bands. Radioluminescence spectra examine the changes of particular emissions as a function of temperature. Finally, parameters of traps detected in thermally stimulated luminescence are determined by decompositions of the recorded glow curves.

Angular dependence of columnar recombination in high pressure xenon gas using time profiles of scintillation emission

The angular dependence of columnar recombination in xenon (Xe) gas, if observed for low energy nuclear tracks, can be used for a direction-sensitive dark matter search. We measured both scintillation and ionization yields to study columnar recombination for 5.4 MeV alpha particles in a high pressure gas detector filled with Xe gas at a pressure of 8 atm. Because the recombination photons are emitted several microseconds after de-excitation, the scintillation photons are separated into fast and slow components. While the fast component is not dependent on the track angle relative to the drift electric field, the slow component increases when the track is aligned with the electric field. This result indicates that the track angle relative to the electric field can be reconstructed from the scintillation time profile.

Improved search for two-neutrino double electron capture on 124Xe and 126Xe using particle identification in XMASS-I

We conducted an improved search for the simultaneous capture of two $K$-shell electrons on the $^{124}$Xe and $^{126}$Xe nuclei with emission of two neutrinos using 800.0 days of data from the XMASS-I detector. A novel method to discriminate $\gamma$-ray/$X$-ray or double electron capture signals from $\beta$-ray background using scintillation time profiles was developed for this search. No significant signal was found when fitting the observed energy spectra with the expected signal and background. Therefore, we set the most stringent lower limits on the half-lives at $2.1 \times 10^{22}$ and $1.9 \times 10^{22}$ years for $^{124}$Xe and $^{126}$Xe, respectively, with 90% confidence level. These limits improve upon previously reported values by a factor of 4.5.

Scintillation properties of Gd3Al2Ga3O12:Ce (GAGG:Ce): a comparison between monocrystalline and nanoceramic samples

In this Communication the behavior of two types of Gd3Al2Ga3O12:Ce samples under gamma and X-ray excitation is compared. Single crystals of GAGG:1%Ce have been grown by the Czochralski technique, while nanoceramic pills of GAGG:1%Ce have been fabricated by the LTHP sintering from nanocrystalline powders prepared by the Pechini method. The results of pulse height, scintillation time profile, radioluminescence as a function of temperature, and low temperature thermoluminescence measurements, are reported, indicating that monocrystals are still a better choice for scintillator application, nevertheless some of the properties of nanoceramics are indeed promising and there should be a room for improvement.

Effect of Lu-to-Y ratio and Mo coactivation on scintillation properties of LuYAG:Pr and LuAG:Pr,Mo crystals

In this paper the basic scintillation and thermoluminescence properties of LuYAG:Pr and LuAG:Pr,Mo crystals are reported. It is shown that, primarily, both materials display significantly higher scintillation yields than their prototype LuAG:Pr. The results of radioluminescence, low and high temperature thermoluminescence, and scintillation time profile measurements are analyzed quantitatively to allow us a better understanding of the scintillation process in LuYAG:Pr and LuAG:Pr,Mo, as well as to let us propose or verify possible explanations of the observed yield enhancement.

Scintillation properties of μPD-grown Y4Al2O9:Pr (YAM:Pr) crystals

Y4Al2O9:Pr (YAM:Pr) crystals have been grown by the micro-pulling-down method and their scintillation properties have been investigated. YAM:0.1%Pr displays a light yield of about 2000ph/MeV and its scintillation time profile contains a prompt component with a decay time of 23.5ns and a contribution of 20%. Radioluminescence spectra show both fast d–f and slow f–f praseodymium emissions. Low temperature glow curves are complex, consisting of discrete peaks and broad bands related to quasi-continuous trap distributions. Overall scintillation performance of YAM:Pr deteriorates with increasing praseodymium concentration.

Luminescence and scintillation properties of Ce-doped Cs2ZnCl4 crystals

In this study, we have synthesized scintillation materials based on Ce-doped Cs2ZnCl4 crystals. The light yield was enhanced by up to 20% by doping Cs2ZnCl4 with Ce3+ ions. In the scintillation time profiles, fast components exhibited decay time constants on the order of nanoseconds, which was ascribed to Auger-free luminescence (AFL). The light yield of the AFL component decreased at 10mol% Ce3+ concentration, which is mainly attributed to the reabsorption of AFL photons inside the crystals by Ce3+ ions, as seen in the scintillation spectra. Long components had decay time constants of approximately 30ns. In addition, at 10mol% Ce3+ concentration, a prominent band appeared at approximately 500nm in the scintillation spectrum, which was not observed in the photoluminescence spectra. The long components in the scintillation time profiles and the 500nm band in the scintillation spectra were tentatively attributed to self-trapped excitons perturbed by Ce3+ ions.

Effect of thermal annealing on light yield, low temperature thermoluminescence, and time profiles of LuAG:Pr scintillator crystals

Measurements of light yield, low temperature thermoluminescence, and scintillation time profiles, performed comparatively on “as grown” and thermally annealed LuAG:Pr samples, are reported. It is shown that traps play an efficient role in the scintillation of LuAG:Pr, being responsible for the yield decrease and introducing a long component to the time profiles. The trap concentrations in the annealed crystals are lower than in the non-annealed ones, which correlates with the yield enhancement.

Eu2+이온을 도핑한 LaCl3결정의 섬광 특성

본 Czochralski 방법으로 새로운 섬광체인 <TEX>$LaCl_3:Eu^{2+}$</TEX> 결정을 육성하고, 육성된 섬광체의 섬광 특성을 조사하였다. 육성한 <TEX>$LaCl_3:Eu^{2+}$</TEX> 결정 구조는 육방정계로서 <TEX>$P_63$</TEX>/m 공간군에 속함을 확인할 수 있었으며, 격자상수는 각각 a = b = <TEX>$7.48{\AA}$</TEX>, c = <TEX>$4.37{\AA}$</TEX>이었다. 335 nm로 여기시킨 <TEX>$LaCl_3:Eu^{2+}$</TEX> 결정의 발광 스펙트럼 파장 범위는 약 370 ~ 640 nm 이었으며, 중심 파장은 430 nm이었다. 형광 감쇠 곡선은 <TEX>$2.82{\pm}0.72{\mu}s$</TEX>의 단일 성분으로 구성되었으며, <TEX>$^{137}Cs$</TEX> 662 keV <TEX>${\gamma}$</TEX>-선에 대한 에너지 분해능은 약 8.8%이었다. In this paper, the scintillation properties of <TEX>$LaCl_3:Eu^{2+}$</TEX> crystal were investigated as new scintillator. This scintillation material was grown by a Czochralski method. <TEX>$LaCl_3:Eu^{2+}$</TEX> was determined to have a hexagonal <TEX>$P_63$</TEX>/m space group with cell parameters a = b = <TEX>$7.48{\AA}$</TEX>, c = <TEX>$4.37{\AA}$</TEX>. Under 335 nm UV excitation, the crystal shows a broad emission band between 370 nm and 640 nm wavelength range, peaking at 430 nm. At room temperature, the crystal exhibits one exponential decay time component. The component of scintillation time profile of the crystal emission decays with a <TEX>$2.82{\pm}0.72{\mu}s$</TEX> time constant. The energy resolution of the crystal was measured to be 8.8% (FWHM) for <TEX>$^{137}Cs$</TEX> 662 keV <TEX>${\gamma}$</TEX>-rays.