Suitable Scintillator Research Articles

Optical and scintillation properties of Yb-doped La2Hf2O7 crystal grown by core heating method for fiber reading remote-dosimetry system

(La0.99Yb0.01)2Hf2O7 (Yb:LaHO) crystal has been developed by the core heating method as a near-infrared-emitting oxide scintillator for a fiber reading remote-dosimetry system under the high-dose-rate region. This system consists of a scintillator, a long silica optical fiber and a detector unit. Near-infrared-emitting photons can be separated from significant fiber-derived noise mainly observed in the UV–blue range. The noise is generated in the optical fiber itself by gamma-rays and charged particles. The Yb:LaHO crystal had a maximum emission peak at 975 nm when excited by X-rays and a transmittance of approximately 29% at 977 nm. The afterglow intensity of the Yb:LaHO crystal under X-rays was 11% that of Cr:α-Al2O3 (ruby) crystal. We demonstrated the applicability of the remote-dosimetry system with the Yb:LaHO crystal irradiated with gamma rays from a 60Co source with an activity of ∼77 TBq. The signal-to-noise ratio (SNR) of the Yb:LaHO crystal was 1.9 times higher than that of the ruby crystal at ∼ 1 kGy/h, and the lowest limit of the dynamic range was comparable between the Yb:LaHO and ruby crystals. The results of the SNR and afterglow intensity showed that the Yb:LaHO crystal is a more suitable scintillator than the ruby crystal for fiber reading remote-dosimetry systems.

Testing the gallium anomaly

We study the online detection by gallium capture of mono-energetic neutrinos produced by a $^{51}$Cr radioactive source in a scintillation experiment. We find that cerium-doped gadolinium aluminum gallium garnet (GAGG) is a suitable scintillator which contains about 21% of gallium per weight and has a high mass density and light yield. Combined with a highly efficient light detection system this allows tagging of the subsequent germanium decay and thus a clean distinction of gallium capture and elastic neutrino electron scattering events. With 1.5 tons of scintillator and 10 source runs of 3.4MCi, each, we obtain about 760 gallium capture events with a purity of 85% and 680,000 neutrino electron scattering events, where the latter provide a precise normalization independent of any nuclear physics. This configuration would allow to test the gallium anomaly at more than $5\sigma$ in an independent way.

Time-resolved radiation dosimetry using a cerium and terbium Co-doped YAG crystal scintillator

Time-resolved radiation dosimetry is an important factor in ensuring dose delivery during radiotherapy is within the prescribed doses for treatment. One method for time-resolved radiation dosimetry is by radioluminescence (RL) measurement technique using doped-silica optical fibre scintillators. The benefits of RL measurement technique include the capability to measure in real-time, high spatial resolution, and greater adaptability. Additionally, time-resolved dosimetry can be achieved by employing suitable scintillators with short rise and decay time. Silica optical fibre scintillators when doped with suitable dopants, provides the temporal resolution required for pulse-by-pulse dosimetry. Yttrium Aluminium Garnet (YAG) crystal optical fiber doped with Cerium and Terbium are discussed as a possible scintillator for time-resolved radiation dosimetry. The Cerium and Terbium co-doped YAG crystal scintillator samples are irradiated under a 6 MV photon beam from a Elekta Synergy® LINAC. The irradiation doses ranged from 100 cGy/min to 600 cGy/min. The measurements were made using an RL system with a gating time of 1μs. Linear RL response to dose of the irradiated scintillator samples was shown with minimal detectable memory, no afterglow or plateau effects. A rise time of 189.3 ns and a decay time of 260 ns were recorded, indicating promising potential for time-resolved radiation dosimetry.

Potential for a precision measurement of solar pp neutrinos in the Serappis experiment

The Serappis (SEarch for RAre PP-neutrinos In Scintillator) project aims at a precision measurement of the flux of solar pp neutrinos on the few-percent level. Such a measurement will be a relevant contribution to the study of solar neutrino oscillation parameters and a sensitive test of the equilibrium between solar energy output in neutrinos and electromagnetic radiation (solar luminosity constraint). The concept of Serappis relies on a small organic liquid scintillator detector (sim 20 m^3) with excellent energy resolution (sim 2.5% at 1 MeV), low internal background and sufficient shielding from surrounding radioactivity. This can be achieved by a minor upgrade of the OSIRIS facility at the site of the JUNO neutrino experiment in southern China. To go substantially beyond current accuracy levels for the pp flux, an organic scintillator with ultra-low {^{14}hbox {C}} levels (below 10^{-18}) is required. The existing OSIRIS detector and JUNO infrastructure will be instrumental in identifying suitable scintillator materials, offering a unique chance for a low-budget high-precision measurement of a fundamental property of our Sun that will be otherwise hard to access.

Ge-doped silica optical fibre for Time Resolved Radiation Dosimetry

Time-resolved radiation dosimetry in radiotherapy helps determine the quality of delivery of patient prescribed doses. Earlier reports on doped silica optical fibres as scintillators in radioluminescence (RL) based radiation dosimetry have indicated particular merits, including versatility, robustness, high spatial resolution, wide dynamic range, and the ability for real-time measurements. Time-resolved radiation dosimetry requires high temporal resolution, enabled using a suitable scintillator and high-speed electronics. We report on the potential of Ge-doped optical fibres as a suitable scintillator to be adopted for use in a time-resolved radiation dosimetry system. High-energy clinical X-ray beams (6 MV) were used to irradiate the Ge-doped optical fibre samples. RL responses were recorded for six dose-rates (between 100 MU/min and 600 MU/min) delivered by a Varian 2100 C/D linear accelerator. The photon-counting circuit gating time was set at its shortest capability of 100 μs? The Ge-doped optical-fibre scintillator showed linear RL response, with minimal observable memory and afterglow and plateau effects. The fluorescence lifetime analysis, demonstrate a calculated rise time of 590.1 ns and a decay time of 0.423 μs, indicating superior performance compared to other scintillator forms. These results demonstrate the potential for the Ge-doped optical-fibre scintillator to be used in a time-resolved radiation dosimetry system.

Geant4 ile İnorganik Kristal Sintilatörler için Enerji Çözünürlüğünün Reflektör Malzemesine Bağımlılığı Üzerine Çalışma

The scintillator has played a primary role as the ideal device for the detection and measurement of particles and radiation in modern physics. With the development of experimental physics, the demand for new improved scintillating materials for several types of applications has kept increasing. High efficiency, fast scintillation and good energy resolution are among the most desired specifications as to a good scintillator. Yet, a variety of scintillators can be preferred depending on the precise specifications of the application considered. If the case is that the detection of gamma rays and high-energy electrons or positrons, inorganic crystals are exceptionally suitable scintillator because highly intense light outputs and the strong stopping power enable these type of crystals to provide better energy resolution among all scintillators. In this study, a scintillation detector consisting of inorganic crystal scintillator material (NaI:Tl and CsI:Tl) was modeled with the help of Geant4 scientific toolkit to determine if the energy resolution of the inorganic crystal scintillator detector is dependent on crystalline size and reflector material. In each simulation, different sized crystal covered with a variety of reflector type was exposed to the same energy gamma radiation; the resulting energy spectrum was evaluated and compared to others obtained.

Comparison of light outputs, decay times, and imaging performance of a ZnS(Ag) scintillator for alpha particles, beta particles, and gamma photons

ZnS(Ag) is a scintillator mainly used for alpha particle detection because of the high light output for alpha particles. However, the light output and decay times of ZnS(Ag) for beta particles or gamma photons are not obvious. We therefore measured and compared the light outputs and decay times of ZnS(Ag) for beta particles or gamma photons with that for alpha particles. We measured the pulse height distribution and decay times of ZnS(Ag) for Am-241 alpha particles (5.5 MeV), St-Y-90 beta particles (2.28-MeV maximum energy), and Cs-137 gamma photons (0.66 MeV). The relative light output/MeV for the beta particles and gamma photons was ~2%–~5% of that for alpha particles. Decay time for the beta particles and gamma photons was 2.7 ns–2.8 ns, while that for alpha particles was 61 ns. With the different decay times, pulse shape discrimination of the alpha and beta particles was possible for the ZnS(Ag) radiation-imaging detector. We confirmed that ZnS(Ag) is a suitable scintillator for the detection of alpha particles using energy discrimination as well as pulse shape discrimination.

Preparation and scintillating study of ZnO: Hf ceramic to gamma rays

In this work pure and Hf-doped ZnO nanopowders were synthesized by cost-effective sol-gel technique to prepare ceramic pellets by isostatic pressing. Structural, optical and morphological properties of prepared samples were examined by XRD, FESEM, TEM, EDX, UV–vis, FTIR, Raman and PL measurements. Also the scintillation sensitivity of ceramics was studied by a 60Co radiation source. X-ray diffraction pattern analysis confirmed the hexagonal wurtzite structure of samples; Rietveld refinement for crystallite structure determined the lattice parameters of the nanopowders. FTIR and Raman results confirmed the presence of functional group and chemical bonding attributed to ZnO. FESEM image revealed that the size of HZO nanoparticles was obtained a bout 62 nm. For the first time prepared HZO ceramic showed suitable scintillation sensitivity to gamma ray and exhibited strong violet, blue and red emissions at room temperature. Fabricated ceramic showed good characteristics that can be applied for future photonic applications.

Investigation into a suitable scintillator and coded-aperture material for a mixed-field radiation imaging system

Monte-Carlo modelling (MCNPX) methods have been employed to conduct an investigation into a suitable scintillator and coded-aperture material for a scintillator based mixed-field radiation imaging system. Single stilbene crystal, pure and 6Li-loaded plastic scintillators were simulated and their neutron/gamma detection performance compared when exposed to the spontaneous fission spectrum produced by 252Cf. The most suitable candidate was then incorporated into a scintillator based mixed-field coded-aperture imaging system. Coded-aperture models made of three W and 113Cd compositions were tested in different neutron/gamma environments with a square W collimator modelled around the aperture. Each simulation involved recording the interactions of neutron events in organic solid scintillator, whose neutron/gamma detection performance was assessed prior to the coded-aperture material investigation. Three coded-aperture material compositions have been tested with the simulated 252Cf spontaneous fission as well as 241AmBe neutron sources. Results generally claim very good detection sensitivity and spatial resolution for the radioactive sources located in the centre of the aperture.

Bismuth germanate coupled to near ultraviolet silicon photomultipliers for time-of-flight PET

Bismuth germanate (BGO) was a very attractive scintillator in early-generation positron emission tomography (PET) scanners. However, the major disadvantages of BGO are lower light yield and longer rise and decay time compared to currently popular scintillators such as LSO and LYSO. This results in poorer coincidence timing resolution and it has generally been assumed that BGO is not a suitable scintillator for time-of-flight (TOF) PET applications. However, when a 511 keV photon interacts in a scintillator, a number of Cerenkov photons are produced promptly by energetic electrons released by photoelectric or Compton interactions. If these prompt photons can be captured, they could provide a better timing trigger for PET. Since BGO has a high refractive index (increasing the Cerenkov light yield) and excellent optical transparency down to 320 nm (Cerenkov light yield is higher at shorter wavelengths), we hypothesized that the coincidence timing resolution of BGO can be significantly improved by efficient detection of the Cerenkov photons. However, since the number of Cerenkov photons is far less than the number of scintillation photons, and they are more abundant in the UV and blue part of the spectrum, photosensors need to have high UV/blue sensitivity, fast temporal response, and very low noise in order to trigger on the faint Cerenkov signal. In this respect, NUV-HD silicon photomultipliers (SiPMs) (FBK, Trento, Italy) are an excellent fit for our approach. In this study, coincidence events were measured using BGO crystals coupled with NUV-HD SiPMs. The existence and influence of Cerenkov photons on the timing measurements were studied using different configurations to exploit the directionality of the Cerenkov emissions. Coincidence resolving time values (FWHM) of ~270 ps from 2 × 3 × 2 mm3 BGO crystals and ~560 ps from 3 × 3 × 20 mm3 BGO crystals were obtained. To our knowledge, these are the best coincidence resolving time values reported for BGO to date. With these values, BGO can be considered as a relevant scintillator for TOF PET scanners, especially if photodetectors with even better near UV/blue response can be developed to further improve the efficiency of Cerenkov light detection.

Signal pulse emulation for scintillation detectors using Geant4 Monte Carlo with light tracking simulation.

The anode pulse of a photomultiplier tube (PMT) coupled with a scintillator is used for pulse shape discrimination (PSD) analysis. We have developed a novel emulation technique for the PMT anode pulse based on optical photon transport and a PMT response function. The photon transport was calculated using Geant4 Monte Carlo code and the response function with a BC408 organic scintillator. The obtained percentage RMS value of the difference between the measured and simulated pulse with suitable scintillation properties using GSO:Ce (0.4, 1.0, 1.5 mol%), LaBr3:Ce and BGO scintillators were 2.41%, 2.58%, 2.16%, 2.01%, and 3.32%, respectively. The proposed technique demonstrates high reproducibility of the measured pulse and can be applied to simulation studies of various radiation measurements.

An investigation into a suitable scintillator for localising neutron capture within a detector

Using Monte-Carlo modelling, an investigation into a suitable loaded scintillator for localising neutron capture in a novel neutron survey meter has been undertaken. A comparison of estimated neutron capture location in a scintillator with Geant4 and MCNP simulations was undertaken and a good general agreement between the two models was observed. The interactions of γ emissions from neutron capture in the scintillator are investigated. The results show that the γ emission from neutron capture will not aid neutron capture localisation and will only inhibit it. It is observed that the lithium-loaded scintillator has the lowest neutron capture efficiency when compared with boron and gadolinium scintillators. However, it is the most promising of the detectors investigated in this research for use in a novel neutron survey meter design.

Ytterbium-based scintillators, a new class of inorganic scintillators for solar neutrino spectroscopy

The observed deficit of the solar neutrino flux is now well established. This puzzling problem of today's particle physics could be resolved soon. The most likely explanation would be the vacuum neutrino oscillation phenomenon, indirectly proving the non-zero mass of these fleeting particles. Following the proposition of Raghavan of using 176Yb as a target for low-energy solar neutrino spectroscopy, an intense R&D work has started a few years ago to define a suitable scintillator incorporating a large amount of ytterbium. Recently, the observation of UV scintillation in mixed yttrium/ytterbium aluminium garnets opened the field of investigation to a new class of scintillating crystals with interesting luminescence properties, very attractive not only for neutrino physics but also for radiation detection, in general. Their luminescence properties present some peculiarities that make them interesting by themselves.

A new 64-channel area detector for neutrons and gamma ray

The multi-channel photomultiplier (Philips XP1702) can be utilized as a high resolution area detector for thermal neutrons and high energy gamma rays. This detector type is needed, e.g. for special neutron scattering experiments and for the PET method applied to small animals. In various test measurements this will be demonstrated by coupling suitable scintillators (NaI, BGO, and /sup 6/LiI single crystals and /sup 6/Li-glass) and dispersers to the photocathode and by feeding the 64 output signals of the PM into a resistor network via voltage-to-current converters. The final interpolated position per event is determined by pulse height division of the four amplified signals taken from the corners of the network. Experimental results concerning the achievable spatial resolution, the homogeneity and the linearity of the detector response and of the quantum efficiencies are presented. Light experiments with well collimated pulsed rays and with beams of different spot sizes at the photocathode are helpful to explain the measured properties of this new neutron and gamma ray detector.

Detection of charged particles and X-rays by scintillator layers coupled to amorphous silicon photodiode arrays

Hydrogenated amorphous silicon (a-Si:H) p-i-n diodes with transparent metallic contacts are shown to be suitable for detecting charged particles, electrons, and X-rays. When coupled to a suitable scintillator using CsI(Tl) as the scintillator we show a capability to detect minimum ionizing particles with S N ∼ 20 . We demonstrate such an arrangement by operating a p-i-n diode in photovolaic mode (reverse bias). Moreover, we show that a p-i-n diode can also work as a photoconductor under forward bias and produces a gain yield of 3–8 higher light sensitivity for shaping times of 1 μs. n-i-n devices eevices have similar optical gain as the p-i-n photoconductor for short integrating times (< 10μs). However, n-i-n devices exhibit much higher gain for a long term integration (10 ms) than the p-i-n ones. High sensitivity photosensors are very desirable for X-ray medical imaging because radiation exposure dose can be reduced significantly. The scintillator CsI layers we made have higher spatial resolution than the Kodak commercial scintillator screens due to their internal columnar structure which can collimate the scintillator light. Evaporated CsI layers are shown to be more resistant to radiation damage than the crystalline bulk CsI(Tl).

Liquid scintillation radioassay for low-activity beta-emitter mixtures by the method of least squares

From the practicable viewpoint for environmental radioactivity measurement and monitoring, the liquid scintillation radioassay has been applied to low-level pure-beta and γ-emitter mixtures by using the most probable value theory. In low activity measurement, it is required to select a suitable emulsion scintillator and to deal with the calculated data statistically. Detection limit for a solution sample has been roughly estimated to be 10−2 Bq ml−1.

Amorphous silicon pixel radiation detectors and associated thin film transistor electronics readout

We describe the characteristics of thin (1 μm) and thick (> 30 μm) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays, γ rays and thermal neutrons. For x-ray, γ ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For thermal neutron detection we use thin (2∼5 μm) gadolinium converters on 30 μm thick a-Si:H diodes. For direct detection of minimum ionizing particles and others with high resistance to radiation damage, we use the thick p-i-n diode arrays. Diode and amorphous silicon readouts as well as polysilicon pixel amplifiers are described.

Amorphous silicon based radiation detectors

We describe the characteristics of thin(1μm) and thick (>30μm) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and γ rays. For x-ray, γ ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays.

Image Intensification Applied to Light Microscopy

Although this paper is concerned primarily with the application of image intensification to light microscopy, much of the quantitative evaluation of the intensifier-TV detector system has been derived from applications to x-ray diffraction. The technique converts x-rays to visible light by means of a suitable scintillator. This light is fiber optically coupled to the image intensifier cathode, and intensification is achieved in the usual way. The method is useful where (1) the specimen is weakly diffracting, (2) the x-ray intensity must be kept low or exposure times short in order not to damage the specimen, or (3) dynamic structure studies are involved.

Effects of permeability of polyethylene vials in liquid scintillation counting

The effects of the permeability of polyethylene counting vials on the liquid scintillation counting of radioactive materials and channels ratios have been examined. The count rate of toluene-soluble and water-soluble radioactive material dissolved in a suitable scintillation mixture altered by not more than 5 per cent in 4 days. The sample channels ratio altered only slightly or not at all. Changes in external standard channels ratio varied between 3 and 25 per cent in that time, depending on scintillation mixture and temperature of storage. Changes were in all cases greater if vials containing prepared samples were kept at 20°C than if they were kept at 5°C. If n-hexadecane radioactive standard was dispensed into empty polyethylene vials there was a reduction in counting efficiency related to the delay before adding scintillation mixture; the efficiency fell 5 per cent within 2 hr.