ZnS Scintillator Research Articles

Natural radioactivity and heavy metal contamination in edible fish, shellfish and mollusks at the Bay of Bengal, Kuakata, Bangladesh

In this study, gamma activity concentrations, gross alpha and gross beta activity of natural radionuclides, and heavy metal concentrations were measured in eleven edible marine fish, four shellfish, two mollusks, and a common seaweed sample collected from a local sea fish market and sea beach area of the northern part of the Bay of Bengal, Kuakata, Bangladesh. Using HPGe gamma spectrometry, the activity concentrations of 238U, 232Th, and 40K were measured and found to be 19.7 ± 1.5 Bq/kg, 12.2 ± 0.9 Bq/kg, and 188 ± 15 Bq/kg, respectively, with the 232Th concentration surpassing that of 238U. The ZnS scintillation detector was used to assess the gross alpha and gross beta activity. The average gross alpha activity and gross beta activity were found to be 9.4 ± 1.4 Bq/kg and 26 ± 4 Bq/kg, respectively, with the latter attributed to beta emitting radionuclides's abundance. The activity concentrations of 238U, 232Th, and 40K in the analyzed samples varied in the order of Shellfish > Seaweed > Fish > Mollusks, Seaweed > Shellfish > Mollusks > Fish, and Seaweed > Shellfish > Fish > Mollusks. The annual effective dose due to consumption of analyzed seafood was found to be within the world limit of 2400 μSv/y recommended by UNSCEAR. The main contributor to the annual effective dose was 238U. The excess lifetime cancer risk (ELCR) results were below the permissible threshold of 10−3 for radiological risks. Furthermore, average concentrations of Zn and Mn were higher than WHO/FAO recommended values, and carcinogenic Pb, Cd, Cr, and Hg concentrations were below detection limits, according to heavy metal analysis performed by AAS. The average concentration of heavy metals in all of the seafood samples under investigation was in the order of Zn > Fe > Mn. The calculated hazard index (HI), target hazard quotient (THQ), and estimated daily intake (EDI) were compared to the permissible safety limits.

Design and Development of a Portable Neutron Detection System Based on a 6Li-Doped ZnS(Ag) Scintillator

In this study, the design and development of a portable neutron detection system based on a 6LiF + ZnS(Ag) scintillator was carried out. The detector system was first modeled using the Monte Carlo simulation code MCNP. As a result of the detector simulation, the materials and photomultiplier tubes (PMTs) were supplied for the system, and the material properties and thicknesses were optimized for the best scintillator, with the EJ-420 (Eljen Technology), consisting of 95% 6Li dispersed in ZnS(Ag), chosen because it has a distinctive feature with regard to high thermal neutron detection efficiency. Since this material has been shown to offer a significant advantage in favor of neutron detection in mixed radiation fields with gammas and neutrons, the pulse shape discrimination method was employed. To achieve this, a proper electronic circuit was developed to discriminate the pulses from neutrons and gammas. In the experimental step, the EJ-420 scintillator with a 50-mm diameter was optically coupled with a special fast PMT (Hamamatsu H1949-51 model). In conclusion, this study, which underlines the performed simulations for a neutron detector configuration, gives the obtained experimental results showing discrimination capability in neutron/gamma detection using a 241Am-Be neutron source. The results show that the EJ-420 is a good scintillator due to its highly enriched 6Li transmator, which results in more effective neutron measurements when a portable neutron detector design is chosen.

Measurement of gross alpha radioactivity levels and estimation of annual effective dose in hazelnut kernels

Abstract The present study investigates gross alpha (GA) radioactivity levels in hazelnut kernels purchased from markets in Türkiye. 10 different hazelnut samples were crushed and made ready for counting. The alpha counts were obtained via ELSEC 7286 low level alpha counter with ZnS scintillator and EMI 6097B photomultiplier tube. The samples were placed in front of the detector to acquire the counts. All samples were counted isochronously. In addition to the GA activity measurement, total annual effective dose (AED) value for different age groups owing to ingestion was calculated for each sample. It was observed that the GA radioactivity levels in the samples were quite low, and total AED values were considerably lower than the WHO worldwide average AED value (290 μSv/year).

Gross alpha/beta activity concentrations in imported bottled drinking water in Saudi Arabia

This research assessed the gross alpha and beta activity levels in bottled drinking water imported to Saudi Arabia, applying the evaluation process recommended by the World Health Organization (WHO). The WHO's approach for examining alpha and beta activity in drinking water consists of an initial phase of screening for gross alpha and beta levels to determine the need for further analysis. This is followed by a detailed assessment of specific radionuclide concentrations if initial screening levels are surpassed. The study utilized the evaporation method as a standard procedure to quantify the gross alpha and beta activity levels. Each water sample underwent evaporation, after which the activity levels of the residual matter were measured. Gross alpha activity was analyzed using a ZnS (Ag) scintillator detector system, while gross beta activity levels were gauged using a proportional counting system. The methodologies for determining gross alpha and beta activities align with the International Organization for Standardization (ISO) standards ISO 9696 and ISO 9697, respectively. The research identified the maximum alpha and beta activity levels to be 0.18 Bq/L and 0.34 Bq/L, respectively. These values were evaluated against the WHO guidance threshold values of 0.5 Bq/L for gross alpha and 1.0 Bq/L for gross beta activities, confirming that the exposure remains below the individual dose criterion of 0.1mSv/year. The estimated committed effective doses fell under the WHO's advised cap of 0.1 mSv annually, indicating the safety of the water samples for consumption. The study recommends the analysis of a larger set of samples over extended periods for increased assurance.

Applicability of an Ionising Radiation Measuring System for Real-Time Effective-Dose-Optimised Route Finding Solution during Nuclear Accidents

The reduction in the effective dose of evacuated injured persons through contaminated areas of nuclear accidents is an essential emergency services requirement. In this context, there appeared a need to develop a dose-optimised route finding method for firefighting rescue vehicles, which includes the development of a real-time decision support measurement and evaluation system. This determines and visualises the radiation exposure of possible routes in a tested area. The system inside and outside of the vehicle measures the ambient dose equivalent rate, the gamma spectra, and also the airborne radioactive aerosol and iodine levels. The method uses gamma radiation measuring NaI(Tl) scintillation detectors mounted on the outside of the vehicle, to determine the dose rate inside the vehicle using the previously recorded attenuation conversation function, while continuously collecting the air through a filter and using an alpha, beta, and gamma radiation measuring NaI(Tl)+ PVT + ZnS(Ag) scintillator to determine the activity concentration in the air, using these measured values to determine the effective dose for all routes and all kinds of vehicles. The energy-dependent shielding effect of the vehicle, the filtering efficiency of the collective protection equipment, and the vehicle’s speed and travel time were taken into account. The results were validated by using gamma point sources with different activity and energy levels. The measurement results under real conditions and available real accident data used in our simulations for three different vehicles and pedestrians proved the applicability of the system. During a nuclear accident based on our model calculations, the inhalation of radioactive aerosols causes a dose almost an order of magnitude higher than the external gamma radiation caused by the fallout contamination. The selection of the appropriate vehicle and its route is determined by the spectrum that can be measured at the accident site but especially by the radioactive aerosol concentration in the air that can be measured in the area. In the case of radiation measuring detectors, the shielding effect of the carrier vehicle must be taken into account, especially in the case of heavy shielding vehicles. The method provides an excellent opportunity to reduce the damage to the health of accident victims and first responders during rescue operations.

Logistic regression-time–frequency algorithm for α/β discrimination in silicon photomultiplier–based Phoswich detectors

Phoswich (phosphor sandwich) systems composed of ZnS(Ag) and plastic dual scintillators have the ability to distinguish α and β particles via digital pulse-shape discrimination. In this work, a novel logistic regression algorithm based on time–frequency features (LR-TF) is presented and evaluated for its ability to digitally discriminate α and β particles in a mixed field. The LR-TF algorithm employs the charge comparison method (CCM) and Fourier gradient analysis (FGA) to extract time–frequency features from pulse shapes, thereby constructing a logistic regression model. Training of the model is shown to enable the discrimination α and β particles. The CCM, FGA, and LR-TF were applied to thousands of pulses obtained with a data acquisition system based on a Phoswich coupled with a silicon photomultiplier. The experimental results show that the LR-TF algorithm provided the best overall performance with misidentification ratios of 1.9 % and 0.63 % for α particles and β particles, respectively, achieving a figure of merit of 4.30, and an area under the receiver operating characteristic of 0.996.

Development of local-power-free, remote α-particle detection using optical fibers.

We demonstrate the application of fluorescence optical fiber coupled to a telecom grade fiber as a sensor for alpha particles using alpha-specific ZnS(Ag) scintillation materials whose wavelength is down-shifted into a low-loss region of the telecom grade fiber transmission band. Telecom-grade fiber optics offer a solution for sensing alpha radiation in deep repositories and cask storage for radioactive materials due to the stability of SiO2 under normal environmental conditions and its relative radiation hardness at low radiation doses. Long-term nuclear waste storage facilities require sensors for the detection of leakage of radioactive materials that are maintenance-free, do not require power and can survive with no 'wear out' mechanisms for decades. By accomplishing the wavelength transformation, we maximize efficiencies in the detection of α-particles and signal transport and can detect alpha scintillation at distances on the order of >1km with a sensor that is ~3% efficient and can be easily scaled as a sensor array. This paper describes the construction and testing of the sensor including manufacture of the controlled thickness films, verification of the wavelength shift from 450to 620nm and optimization of the sensitivity as a function of thickness. We also model the relative sensitivity of the film as a function of film thickness, and we demonstrate a signal-to-noise ratio of 10 at a range of greater than 1km.

Development of an event-by-event based Li–ZnS(Ag) neutron imaging detector with selective neutron detection capability

High sensitivity and high resolution is desired in such technologies as neutron radiography. However, the contamination of gamma photons in neutron images decreases the accuracy of neutron radiography. To solve this problem, we developed an event-by-event based neutron imaging system that can selectively detect neutrons. The developed neutron imaging system consists of an Li–ZnS(Ag) scintillator plate optically coupled to a flat panel photomultiplier tube (FP-PMT) with a light guide. Scintillation light emitted from the Li–ZnS(Ag) by the interaction with neutron-induced particles is used to calculate the position based on the center of mass calculations. The spatial resolution of the neutron imaging detector is ∼2.3 mm FWHM, and the sensitivity for 252Cf at 2 cm from the source with 2-cm-thick polystyrene is 20 cps/MBq. Background count fraction from 60Co gamma photons was 0.2 %. For various types of neutron absorption phantoms, high-contrast and high-resolution neutron images are obtained with the developed neutron imaging detector using a252Cf neutron source.

Development of a large-area alpha imaging detector for hand and foot monitors

— This paper describes the development of a large-area imaging detector capable of measuring the detailed distribution of alpha particles on hands and feet for use in entry/exit control monitors in decommissioning sites such as the Fukushima Daiichi Nuclear Power Plant. The detector was developed using a commercially available ZnS(Ag) scintillator and an electron multiplying CCD camera. The effectiveness of the detector was evaluated by measuring several types of radiation sources, and the results showed that it was possible to detect the position of alpha particles in a very short time, and contamination levels of up to 11 Bq/cm2 could be visualized. As a result of the minimal detectable surface activity concentration evaluations, 2.0 min or more is required to achieve 4 Bq/cm2, and 25.0 min or more is required to achieve 0.4 Bq/cm2. The field of view of the detector was also checked, and it was confirmed that the setup had a field of view that could cover most of the hand and the sole of the shoe. This detector is expected to be useful for preventing internal uptake and decontamination.

High-Efficiency ZnS: Cu+, Al3+ Scintillator for X-ray Detection in a Non-Darkroom Environment.

Scintillator is a key component in X-ray detectors that determine the performance of the devices. Nevertheless, due to the interference of the ambient light sources, scintillators are only operated in a darkroom environment currently. In this study, we designed a Cu+ and Al3+ co-doped ZnS scintillator (ZnS: Cu+, Al3+) that introduces donor-acceptor (D-A) pairs for X-ray detection. The prepared scintillator displayed an extremely high steady-state light yield (53,000 photons per MeV) upon X-ray irradiation, which is 5.3 times higher than that of the commercial Bi4Ge3O12 (BGO) scintillator, making it possible in X-ray detection with the interference of ambient light. Furthermore, the prepared material was employed as a scintillator to construct an indirect X-ray detector, which performed a superior spatial resolution (≈10.0 lp/mm) as well as persistent stability under visible light interference, demonstrating the feasibility of the scintillator in practical applications. Therefore, this research presented a convenient and useful strategy to realize X-ray detection in a non-darkroom environment.

Atomistic modeling to the investigation of irradiation effect on optical properties of LiI/ZnS scintillator in a research reactor-based neutron radiography facility

Scintillation material presents a variety of applications used in radiation environments such as dosimetry, spectrometry, and radiography facility. Neutron radiography is a non-destructive testing (NDT) method that uses a proper scintillator such as LiI/ZnS for neutron detection. This paper investigated the effect of neutron-induced point defects on the optical properties of this scintillator used in TRR’s neutron radiography system. The combination of Monte Carlo and atomistic modeling methods was utilized in this regard. The results showed that the induced point defects lead to a more than 10 and 22% reduction in the refractive index and reflectivity of the LiI scintillator at optical wavelength respectively. Moreover, the refractive index of the ZnS scintillator decreases more than 6.4 % by Zn interstitial, Zn vacancy, and S vacancy and increases 8.9 % by S interstitial at optical wavelength.

A thermal neutron detector array communication protocol

To assess hadronic and electromagnetic components from extensive air shower events (EAS), 16 6Li-based ZnS (Ag) scintillator detectors combine into a thermal neutron detector array. After a shower event, each scintillator screen can concurrently catch neutrons and electrons, producing a succession of electrical signals with different pulse shapes. These signals are sampled by 16 oscilloscope-like circuits and sent over a single serial link, where EAS-related sampling results may fill each channel's memory. However, there are presently no specific studies to address data congestion in such random signal digitizers. Here, we demonstrate that decreasing the sampling rate on the trailing edge can compress data size while preserving pulse shapes and that optimizing the read/write time of memories can enhance transmission speed between asynchronous clock domains. According to test results, the 100 MHz serial transceiver can send 1996 pulses per second when only receiving data from one channel at 50 MHz rates, and it can send 242 pulses per second when simultaneously receiving data from 32 channels (16 × 2). This method increases transmitting speeds 2.3 times over previously employed algorithms, and the compressed rate reaches 97.74%. In addition, we found that the total error rate is lower than 10–10. Our findings also show how memory controllers would probably operate in data flows of 32 channels, predicting the slower writing time and the faster reading time that can complete sending a packet of one channel in the shortest time. We anticipate that our assay can help more detector arrays that require waveform transmission.

Direct Detection of Alpha Particles with Solid-State Electronics

Alpha-particle sources are widely used in industrial and medical applications. Such applications include smoke detectors, static charge eliminators, and radiation therapy. This paper is concerned with the detection of alpha particles. A number of techniques are known for the detection of alpha particles. Those techniques include the Geiger–Müller tube, the ZnS scintillator, the air-filled ionization chamber, and the spark chamber. All the techniques that are currently known are based on the interaction of the ionizing radiation with matter. Charged particles, such as alpha particles, upon entering a medium (such as air), encounter many collisions with bound electrons and lose kinetic energy in the process. The atoms of the medium also become ionized, and a large number of free electrons are released inside the medium. The theory describing the interaction of ionizing radiation with matter is well known and includes formulas such as the Bethe-Bloch formula for the stopping power of matter and formulas for calculating the range of the ionizing radiation in matter. Essentially, all the known techniques for the detection of alpha particles are based on detecting the presence of free electrons inside the medium. This paper presents a new technique for the detection of alpha particles that does not depend on the theory of the interaction of alpha particles with matter. Instead, the technique is based on the direct detection of the positive charge that is carried by the alpha particles. Furthermore, it is the objective of this paper to demonstrate that the direct detection of the charge carried by alpha particles can be done with a tiny and inexpensive component: a metal–oxide–semiconductor field-effect transistor (MOSFET).

Assessment of gross alpha/beta activity in tap water of Dhaka city using ZnS (Ag) scintillation detector and concomitant health hazard

ABSTRACT Quantification of gross alpha and beta-emitting radionuclides in drinking water helps to understand the water quality as well as the long-term exposures to human health. The gross alpha and beta activity concentrations have been measured in 35 tap water samples taken from different residential areas of Dhaka city in the year 2020–2021. The measurement was performed using a dual phosphor Zinc Sulphide Scintillation Detector, ZnS(Ag). The activity of gross alpha of the collected tap water samples ranged from 0.45 ± 0.04 to 16.53 ± 0.01 mBq/L with an average value of 7.22 ± 0.43 mBq/L, which is below the WHO recommended limit of 0.5 Bq/L (WHO, 2011) or 0.1 Bq/L (WHO, 1978). Furthermore, the activity of gross beta in the tap water samples ranged from 3.26 ± 1.25 to 57.99 ± 1.98 mBq/L (mean 30.78 ± 1mBq/L) which is below the WHO recommended limit of 1 Bq/L (WHO, 2011). The total annual equivalent dose due to tap water was found below the WHO recommended dose limit of 100 µSv/y due to radionuclides in water. Present results may help to create baseline data for gross alpha and beta activity in drinkable water in Bangladesh and also for further analysis in identifying specific radionuclides.

RESPONSE OF PLASTIC TRACK DETECTOR OF THE TASTRAK TYPE TO NEUTRONS OF PU–BE SOURCE

The solid-state nuclear track detectors are widely used in a variety of nuclear physics experiments and radiation protection. The paper presents the first results of the newly acquired TASLImage™ neutron dosimetry system at the Slovak University of Technology in Bratislava. A comparison of experimental and calculated responses of a TASTRAK plastic nuclear track detector to neutron spectrum of Pu-Be source is presented. The ambient dose equivalents determined by the TASLImage™ system are compared with the ones measured by the NuDET-ENE neutron detector based on the use of ZnS(Ag) scintillator covered with a thin film of 6LiF thermal neutron converter accommodated inside the HDPE moderator. The first results are concluded, and further research needs are identified.

Development of a capillary plate based fiber-structured ZnS(Ag) scintillator

Silver-doped zinc sulfide (ZnS(Ag)) is an opaque powder scintillator that is mainly used for detection or imaging of charged particles such as alpha particles. Since ZnS(Ag) is not transparent, the thickness of ZnS(Ag) was limited to ∼10 μm. If a thicker ZnS(Ag) scintillator could be developed, it would be useful for studies such as high-energy particle ion detection as well as beta particle or gamma photon detection. We developed a ZnS(Ag) fiber-structured scintillator using a capillary plate in which ZnS(Ag) powder was encapsulated in the capillaries. The thickness of the capillary plate was 400 μm, and the light produced in ZnS(Ag) escaped from the capillaries, spread through the transparent lead glass area, and reached the opposite side of the plate; consequently, the opaque character and absorption of light could be avoided. The amount of light emitted from the capillary plate based fiber-structured ZnS(Ag) was almost the same as that of a commercially available ZnS (Ag) film, but the detection efficiency was about 1/5 (∼ 20%). The amount of light emitted from beta particles and gamma photons per MeV was less than 1% of that from alpha particles. The spatial resolution of the developed capillary plate based fiber-structured ZnS(Ag) scintillator for 5.5 MeV alpha particles was ∼200 μm FWHM. Imaging of the slits and light spots from alpha particles could be achieved with the developed scintillator combined with an electron-multiplied charge-coupled device (EM-CCD) camera. The developed capillary plate based fiber-structured ZnS(Ag) will be useful for detecting high-energy particle ions.

Monitoring System Of Radon Gas Concentration In Groundwater In Real-Time For Earthquake Detection

Several studies that have been carried out can identify signs of an impending earthquake. One example of changes in the concentration of Rn (Radon) in the area affected by an earthquake. The purpose of this study is to design and create a prototype of an earthquake early detection system through real-time measurement of radon gas concentrations in the air where the measurement data results can be uploaded to the internet network and viewed by users in real time through a site. To detect it, a scintillation detector is used, in the design of the detector system the ZnS(Ag) scintillation type will be used. Data analysis was carried out in several ways, stability analysis of the count by measuring n times at the same concentration of radon gas and counting time, counting efficiency, calibration of counting and detection of limits. The data monitoring system is carried out through the website in real-time. Data is sent using an internet provider with sim900 every minute to 58 every hour. From the tests carried out on tap water continuously in the BATAN market area for 24 hours, it can be seen on the site that the average concentration value of Radon compounds in tap water at that location is 59.91 Bq/M3 where the total concentration is still below the threshold value. set by the ICRP (International Commission on Radiological Protection) is around 200 Bq/M3.

Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 ± 2.2 μmFWHM with a zoom range of 5 ×. Also, the spatial resolution for the plutonium dioxide particle was 302.7 ± 4.6 µmFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha–beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.

A numerical model to predict pulse height distribution of alpha particles in thin ZnS(Ag) scintillators

The SnowWhite7 numerical model was developed to predict pulse height distribution from multicrystalline ZnS(Ag) scintillators exposed to alpha particles. The model, implemented in LabView, treats the following effects: charged particle energy loss, stopping-power-dependent light yield, and light self absorption in the multicrystalline matrix. SnowWhite7 was validated against experimental data obtained with scintillators manufactured at INFN-LNF and having thickness from 1.6 mg⋅cm−2 up to about 10 mg⋅cm−2. The scintillation light output was collected using a commercial photomultiplier and a digitizer. SnowWhite7 internal parameters were adjusted to satisfactorily match the experimental spectra. SnowWhite7 will be used in a broader project on the design of neutron sensitive scintillators based on ZnS(Ag) combined with 6LiF.

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.