Scintillation Efficiencies Research Articles

Scintillation and structural properties of copolymers and mixtures of styrene, 9-vinylcarbazole and 4-vinylbenzyl chloride based plastic scintillators

The research team has developed new plastic scintillators in the form of microspheres, called PSm, by combining styrene, 9-vinylcarbazole (VK), and 4-vinylbenzyl chloride (VBC). The primary objective of this study was to explore the feasibility of incorporating the fluorescent solute (VK) into the polymer structure to prevent its leaching out when PSm are utilized in liquid flow through detection systems or organic solvents. The secondary aim was to examine the impact of adding the chlorine functional group to the scintillation polymer, with the intention of replacing it with an extractant in the future to create covalently linked PSresins.The findings of the study reveal that the homopolymer of polyvinylcarbazole (PVK) performs poorly while used as a unitary scintillator system for plastic scintillation measurements. However, the incorporation of monomers in the form of copolymers with styrene has a more significant impact on scintillation properties compared to the mixture of homopolymers. In the case of 9-vinylcarbazole (VK), its presence at a weight proportion of 10% leads to an increase in scintillation efficiencies, although it is still inferior to the classical PS. Conversely, the situation is different for 4-vinylbenzyl chloride (VBC), where the chlorine in the copolymer results in higher quenching, and the polymer is also less resistant to organic solvents due to the formation of short polymer chains. For VBC, the mixture of polymers yields better results and enables the production of covalently linked PSresins.

Eu3+-doped gadolinium borate glass system development for optical and scintillation applications

This paper describes the development and characterization of the Eu3+-doped Ba-Na-B glass system with the varying of Gd2O3 concentrations from 0 to 10 mol%. The photoluminescence emission spectra, excited with 393 nm at Eu3+ ions, show strong luminescence with a peak emission wavelength of 613 nm (5D0→7F2). The highest emission intensity is belonged to the glass sample with 2.5 mol% of Gd2O3. The phonon energy of the host glasses, evaluated from the phonon sideband analysis, is 1017 cm−1. The emission spectra, excited with 275 nm at Gd3+ ions, show the emission band according to the Gd3+→Gd3+ transition at 311 nm (4P7/2→8S7/2) and show the Gd3+→Eu3+ energy transfer, resulting in the emission of light at the characteristic wavelengths of the Eu3+. The highest photoluminescence emission intensity is belonged to the glass sample with 2.5 mol% of Gd2O3, due to its highest energy transfer efficiency at 59.10%. The emitting light of all the glass samples for both excited with 393 nm (Eu3+) and 275 nm (Gd3+) can be all represented by the x,y color coordinates at (0.65, 0.35) in reddish-orange region. The radioluminescence emission spectra, excited by 50 kV, 30 mA X-ray generator, show the emission bands with Eu3+ characteristics. The highest radioluminescence emission intensity is belonged to the glass sample with 7.5 mol% of Gd2O3 with the highest scintillation efficiencies at 20.61% compared to the BGO sample.

Photoluminescence tuning and scintillation properties of Tb3+/Dy3+ ion-doped SiO2-B2O3-Gd2O3/GdF3-CaO glasses

Tb3+/Dy3+ ions doped SiO2-B2O3-Gd2O3-CaO (SBGOTD) and SiO2-B2O3-GdF3-CaO (SBGFTD) two series of glass were synthesized using a high-temperature melting method. The luminescence and scintillation properties of both glass series were studied through photoluminescence (PL) spectroscopy and X-ray emission spectroscopy. In the two series of glass, the SBGFTD (Dy3+,0.5 mol%) glass sample exhibited the best luminous intensity excited at 378 nm and X-ray. The PL emission intensity and fluorescence decay time of Tb3+ were observed to change, indicating that energy was transferred from Dy3+ to Tb3+ ions. In addition, the integrated scintillation efficiencies of the two series glass samples reached 36.8 (SBGOTD) and 38.2% (SBGFTD) of the Bi4Ge3O12 (BGO) standard sample. The practical application of fluorine-modified borosilicate glass in the fields of luminescence and X-ray detection can be further expanded and improved based on these findings.

Radioluminescence characteristics of Eu2O3 ions activated CaO/CaF2 + La2O3 + P2O5 scintillating glasses

The novelty of this research is to prepare phosphate glasses (10CaO/CaF2 + 20La2O3 + 69P2O5) with the effect of 1 mol% Eu2O3 and the incorporation of 10 mol% CaO (or) CaF2, focusing attention on their structural and optical features, together with their influence in the ultimate scintillation spectral response. When CaO (oxide, OE glass) content is replaced by CaF2 (fluoride, FE glass), changes in density and molar volume measurements are observed, including a decrease in the bands of OH groups in the IR spectral range (2500–4000 cm−1). The results of the optical absorption (OA) of glasses showed various peaks in the ranges of 350–600 nm (UV–Visible) and 1800–2400 nm (NIR). The phonon energies of the OE (1219 cm−1) and FE (1210 cm−1) glasses from the Raman spectra are in good agreement with the value (1222 cm−1) obtained from the excitation (PLE) spectra (7F0 →5D2) of Eu3+ ions. From the emission (PL) spectra of glasses, the surrounding environment of Eu3+ ions is evaluated with respect to (Ω2,4,6) intensity parameters and asymmetric (R/O) ratio. Moreover, the OE and FE glasses emit the highest red-emitting 5D0 → 7F2 transition (∼612 nm) under UV light and X-ray radiations. The decay time due to Eu3+ emission is 2.217 ms for OE glass and 2.329 ms for FE glass. In addition, spectroscopic parameters and (x, y) color coordinates are calculated for both glasses fabricated in this work. Furthermore, temperature-dependent luminescence was studied from 10 K to 550 K and found to high in FE glass. The integrated scintillation efficiencies of OE and FE glasses are about 17 % and 18 % of commercial BGO scintillating crystal.

Response of the GAGG(Ce) scintillator to charged particles compared with the CsI(Tl) scintillator

GAGG(Ce) is a novel scintillator with a fast response and high light output without a hygroscopic nature. It is expected to be a useful detector for charged particles at high-counting rates. However, the response of the GAGG(Ce) scintillator to charged particles has not been fully examined. In the present work, the light output and energy resolution of the GAGG(Ce) scintillator were measured for protons and alpha particles at E p=5–68 MeV and E α=8–54 MeV as well as gamma rays at E γ=662 keV from a 137Cs source. The results were compared with those of the CsI(Tl) scintillator. The scintillation efficiencies dL/dE of the GAGG(Ce) and CsI(Tl) scintillators were obtained and parametrized as a function of linear energy transfer dE/dx.

Activity standardisation of 223Ra

We report here on the primary activity standardisation of a223Ra dichloride solution in equilibrium with its decay daughters. Both the triple-to-double-coincidence-ratio (TDCR) method with an in-house TDCR detector and the CIEMAT-NIST efficiency tracing (CNET) technique with a commercial counter were used. The liquid scintillation efficiencies for both methods are about 6 while the activities they predict with about 0.4% relative standard uncertainty agree within 0.15%. For backup, the solution was also standardised with 4πγ NaI(Tl) integral counting with a well-type NaI(Tl) detector, and efficiencies computed by Monte Carlo simulations using the GEANT code. This simple technique, unused previously for this nuclide, yielded an activity concentration compatible with, but 1% lower than, the one determined by liquid scintillation counting.

Scintillation Efficiency and Position Sensitivity for Radiation Events in Plastic Scintillators

Plastic scintillators (PLSs) are potential materials for the development of a dosimeter based on linear energy transfer (LET) measurement for mixed radiation fields, such as the surroundings of accelerator facilities and in space because PLSs are composed mainly of hydrocarbon molecules, and have the effective atomic number and density similar to those of water and human tissues. In addition, PLSs have a wide range of application in particle physics experiments, owing to their response to all types of radiation (photon, neutron, and charged particles). To use PLSs in designing and constructing an LET spectrometer, essential characteristics of PLSs, such as light yields as a function of deposited energy and radiation species, and the position sensitivity to observe trajectories of incident radiation must be studied. Previously, we performed a procedure for determining the energy deposited in a PLS (EJ-200) for gamma rays from a 137Cs radiation source using Compton Coincidence Technique. In that measurement, the scintillation efficiency, which was determined as a function of Compton electron energy, approaches a saturation value in the high-energy region and decreases in the low-energy region. The decrease in efficiency possibly suggests the nonproportionality between the light yield and deposited energy. In this paper, the scintillation efficiencies, as well as the absolute light yield of PLSs (EJ-200, EJ-212, and EJ-252) are investigated. In addition, the position sensitivity characteristic is studied by using a PLS rod, and photomultiplier tubes (PMTs) are attached to both ends of the rod, and the position of radiation incidence in the rod can be evaluated by using signals from the PMTs.

On the scintillation efficiency of carborane-loaded liquid scintillators for thermal neutron detection

The scintillation efficiency in response to thermal neutrons was studied by loading different concentrations of carborane (0–8.5wt%) and naphthalene (0 and 100g/L) in five liquid organic scintillators. The sample was characterized in Pb and Cd shields under the irradiation of the thermal neutrons from a 252Cf source. A method was developed to extract the net neutron response from the pulse-height spectra. It was found that the order of scintillation efficiencies for both γ-rays and thermal neutrons is as follows: diisopropylnaphthalene>toluene (concentrated solutes)>toluene~pseudocumene~m-xylene. The quench constants, obtained by fitting the Stern–Volmer model to the plots of light output versus carborane concentration, are in the range of 0.35–1.4M−1 for all the scintillators. The Birks factors, estimated using the specific energy loss profiles of the incident particles, are in the range of 9.3–14mgcm−2MeV−1 for all the samples. The light outputs are in the range of 63–86keV electron equivalents (keVee) in response to thermal neutrons. Loading naphthalene generally promotes the scintillation efficiency of the scintillator with a benzene derivative solvent. Among all the scintillators tested, the diisopropylnaphthalene-based scintillator shows the highest scintillation efficiency, lowest Birks factor, and smallest quench constants. These properties are primarily attributed to the double fused benzene-ring structure of the solvent, which is more efficient to populate to the excited singlet state under ionizing radiation and to transfer the excitation energy to the fluorescent solutes.

Birks׳ scaling of the particle light output functions for the EJ 299-33 plastic scintillator

The response of the EJ 299-33 plastic scintillator to energetic charged nuclear particles ranging from isotopes of hydrogen to carbon-12 has been analyzed in terms of Birks׳ semi-empirical approach over the wide range of particle energies from 2 to 20AMeV. It was found that while the original two-parameter scaling involving Birks׳ composite quenching parameter kB and an overall conversion efficiency parameter S may be applicable to select sets of particles, a more universal fit would still require individual scintillation efficiencies Sx for individual particle species and more than just one value of the composite Birks׳ constant kB.

Scintillation Efficiency of Inorganic Scintillators for Intermediate-Energy Charged Particles

We carried out experiments to investigate the light output response of NaI(Tl), CsI(Tl), GSO(Ce) and LYSO(Ce) crystals for intermediate-energy 4 He, 12 C and 40 Ar beams from HIMAC at National Institute of Radiological Sciences. And we investigate the light output of these crystals for several-energy gamma-ray for comparison. From these light output responses, we obtained the relationships between the scintillation efficiency (dL/dx) and the specific energy loss (dE/dx) for each crystal. The scintillation efficiency curves of NaI(Tl) and CsI(Tl) crystal have the peak in a particular dE/dx. On the other hand, the scintillation efficiency curves of GSO(Ce) and LYSO(Ce) crystal decrease with increasing dE/dx. The light output curves of these crystals were systematically reproduced using obtained scintillation efficiencies.

Comparative Study of Plastic Scintillators for Dosimetric Applications

Plastic scintillators are widely studied for radiotherapy dosimetry because of their very interesting properties and especially their water equivalence. Nevertheless, to ensure accurate dose measurements, the properties of the scintillators must be very well known and adapted to this application. We studied six plastic scintillators manufactured by two different companies (Bicron and Amcrys-H) in terms of emission spectrum, light yield, time response, and linearity of the scintillation response with regards to the incident radiation energy. This last data, which is not available for plastic scintillator, is one of the most important in radiotherapy applications because it guarantees the proportionality between the dose deposited in the scintillator and the scintillation intensity. The experimental emission spectra (measured under X-rays) were similar to the manufacturer ones (measured under UV), except for one scintillator which presented incomplete wavelength shifts. This information is important to match the scintillator emission with the photodetector spectral response and to cope with the limiting phenomena of scintillation dosimetry (in particular the Cerenkov radiation). Bicron scintillators showed better scintillation efficiencies (ranging from 64 to 79% of Anthracene) than Amcrys-H ones (ranging from 40 to 63% of Anthracene). On the contrary, the decay times of the scintillators, similar to the ones provided by the manufacturers, were slightly better for the Amcrys-H scintillators (from 4.62 to 9.53 ns ) than for the Bicron ones (from 4.74 to 12.95 ns). This study showed that the response of the scintillation response become linear when irradiated by electrons above 100 keV and photons above 200-250 keV . One of the Bicron scintillators presented a worse criterion of linearity, and one of the Amcrys-H scintillators presented a better criterion. These results clearly show that plastic scintillators are very convenient for radiotherapy where most photons have energy higher than a few hundreds of keV.

Highly efficient solid-state neutron scintillators based on hybrid sol-gel nanocomposite materials

This research highlights opportunities in the formulation of neutron scintillators that not only have high scintillation efficiencies but also can be readily cast into two-dimensional detectors. Series of transparent, crack-free monoliths were prepared from hybrid polystyrene-silica nanocomposites in the presence of arene-containing alkoxide precursor through room temperature sol-gel processing. The monoliths also contain lithium-6 salicylate as a target material for neutron-capture reactions and amphiphilic scintillator solution as a fluorescent sensitizer. Polystyrene was functionalized by trimethoxysilyl group in order to enable the covalent incorporation of aromatic functional groups into the inorganic sol-gel matrices for minimizing macroscopic phase segregation and facilitating lithium-6 doping in the sol-gel samples. Neutron and alpha responses of these hybrid polystyrene-silica monoliths were explored.

Band structure calculations of cerium activated inorganic scintillators

Trivalent cerium has been used extensively in recent years as an activator in crystalline hosts for fast scintillators. The scintillation efficiencies have been found to vary greatly, however. For example, no scintillation is observed from Ce-doped Y2O3 and Lu2O3, the efficiency is low for CeF3, whereas the efficiency is very high for Lu2SiO5:Ce. This behavior has been attributed in large part to the location of the ground 4f and excited 5d levels of Ce3+ with respect to the fundamental band gap of the host. We have performed band structure calculations to predict the band gaps and the location of the Ce and Lu 4f and 5d levels in the fluoride host CeF3 and in the oxide host LuAlO3. Calculations were made using a full-potential linear muffintin orbital (FP-LMTO) approach. We find that Ce 4f levels in CeF3 are several eV above the top of the valence band (VB), thus reducing the probability of hole capture. The Lu 4f levels in LuAlO3 are predicted to be several eV below the top of the VB. Both of these results are in agreement with experiment. Preliminary calculations on LuAlO3:Ce locate the Ce 4f energy levels approximately 3 eV above the VB (O2p) which is not consistent with the high scintillation efficiency of LuAlO3:Ce.

Cerium-doped fluorescent and scintillating ionic crystals

Relaxation of electronic excitations created by the absorption of a high energy photon is analyzed in the case of rare earth crystals. it is shown that the energy transfer to cerium ions strongly depends on the band structure of the system, in particular on the position of the Ce 4f level in the bandgap. The probability of the hole capture by Ce3+ is related to the scintillation efficiency; it is in general weak in fluorides and stronger in oxides. The fact that cerium has two stable valence states Ce3+ and Ce4+ can lead to Ce bound exciton formation and Ce3+ low energy photoionization processes which can influence the fluorescence and scintillation efficiencies of the crystals.

Comparison of two liquid scintillators used for neutron detection

The pulse-shape discrimination capability and the scintillation efficiency of two liquid scintillators, BC519 and NE213 (BC501A) have been compared. Pulse-shape discrimination is not as good with BC519, but for large light pulses it should be adequate in many applications and may be a useful alternative to NE213 because it has a higher ratio of H-to-C- atoms. Within 5% the scintillation efficiencies are the same when the scintillators are excited by protons with energies up to 11 MeV.

Towards two-dimensional brachytherapy dosimetry using plastic scintillator: new highly efficient water equivalent plastic scintillator materials.

Plastic scintillator (PS) has been proposed for both one- and two-dimensional (1D and 2D) dose measurements for radiation therapy applications. For low-energy photon modalities (e.g., brachytherapy), an efficient water equivalent scintillator is needed. To perform 2D measurements, a high localization of the scintillation process is required. Guided by comparison of the mass energy absorption coefficients as a function of energy and of the dose distribution as a function of distance from the radioactive source, as modeled by Monte Carlo photon transport simulation, a small quantity of medium atomic number (Z) atoms (4% Cl) was incorporated in a polyvinyl toluene (PVT) based PS to approximate closely (within 10%) the radiological properties of water in the 20-662 keV energy range. However, the scintillation efficiency of commercial PS mixtures drops as much as 70% when loaded with high atomic number additives. We developed experimental techniques to assess the scintillation efficiency and locality of 15 new PS mixtures. These mixtures differ by the type of the scintillation dyes and the type of compound containing the medium Z atoms (chlorine). To achieve higher material stability, 4-chlorostyrene was used as a loading compound to ensure polymerization with the PVT base. Two of the new PS materials exhibited scintillation efficiencies within 30% of one of the most efficient commercially available products (BC-400), which is not water equivalent at such low energies. These new scintillator materials are promising candidates for the development of an accurate and efficient radiation dosimetry method not only for brachytherapy, but also for superficial and diagnostic applications.

Measurement of scintillation efficiencies and pulse-shapes for nuclear recoils in NaI(Tl) and CaF2(Eu) at low energies for dark matter experiments

Abstract Measurements have been performed with a 2.85 MeV mono-energetic neutron beam of relative scintillation efficiency and pulse-shape for nuclear and electron recoils in NaI(Tl) and CaF2(Eu). Scintillation efficiencies in NaI(Tl) relative to 60 keV gamma events were found to be 27.5±1.8% for Na recoils (recoil energy Erec>4 keV) and 8.6±0.7% for I recoils (Erec>10 keV). Relative scintillation efficiencies in CaF2(Eu) for Ca and F recoils show some evidence for a fall with energy (17% to 8% for F) for 10 keV 〈 t i 〉 of 263±15 ns for Na events (visible energy Evis in the range 2–8 keV and 272±10 ns for I events (2 keV 〈 t i 〉 of 4 keV 〈 t i 〉 for 2 keV

Determination of the conversion efficiency of X-ray luminophores when measuring the intensity of ionizing radiation

Measurements of the conversion efficiency of several inorganic scintillators are presented. Conversion efficiency is defined as the ratio of the total energy of luminescence photons to the energy expended in producing the photons. The measurement method used was based on the measurement of the intensity of the total flux of the characteristic radiation under the constant action of exciting x-rays with prescribed energy, therefore accounting for the contribution of both fast and slow components of de-excitation. Light outputs, relative to the light output of CsI(Tl) are also given for the current and pulsed modes of each scintillator material tested. Conversion efficiencies was obtained by statistical analysis. Results compared well with scintillation efficiencies obtained in referenced experiments for similar materials. The method used to measure efficiencies is concluded to be appropriate for all currently available x-ray luminophores and scintillation crystals. 6 refs., 1 fig., 2 tabs.

Dark matter search with calcium fluoride crystals

A first result on dark matter direct search with calcium fluoride scintillators is presented. The low and high energy spectra are discussed together with the measurements of the fluorine and calcium recoil scintillation efficiencies. Exclusion plots for axial vector coupled WIMPs are derived and compared with previous measurements with NaI and Ge detectors.

Three-dimensional Monte Carlo calculation of the VUV electroluminescence and other electron transport parameters in xenon

The paper presents a set of electroluminescence and other transport parameters calculated using a detailed three-dimensional Monte Carlo method, which simulates the drift of electrons in gaseous xenon (p=760 Torr, T=293 K) under reduced electric fields E/N in the 3 to 16 Td range (E/P approximately 1 to 5 V cm-1 Torr-1), which is the region for secondary scintillation production in xenon filled gas proportional scintillation counters. Results are compared with available experimental or theoretical data as well as an earlier one-dimensional Monte Carlo simulation. The calculated parameters are the excitation and scintillation efficiencies and the reduced light yield, together with mean time intervals, mean drift distances and mean number of elastic collisions between xenon excitation collisions. The authors also present electron drift velocities, mobilities and characteristic energies, as well as mean electron energy and electron energy distribution functions.