Scintillation Cell Research Articles

Environmental dependence of geometrical efficiency for the scintillation cell in radon and thoron measurement.

222Rn is recognized as a matter of international concern for human health risk. Because 220Rn as well as 222Rn coexist in the natural environment, thoron sometimes influences the experiment for radon measurement. It is important to measure radon and thoron separately to evaluate the risk of the exposure to 222Rn. As a discriminative measurement method for 222Rn and 220Rn, a simple technique with a single scintillation cell is well known. However, in recent years, the influence of atmospheric environment on the geometrical efficiency of the scintillation cell has not yet been investigated. In this study, environmental dependence of geometrical efficiency for the scintillation cell in 222Rn and 220Rn measurement was investigated using the Lucas type scintillation cell and Monte Carlo particle simulation. It was found that the influence of temperature and pressure on the geometrical efficiencies were larger than that of relative humidity.

Enhancing time-resolution for radon measurements using airflow-through scintillation cells based on a compartmental model approach.

To overcome the time-resolution limitation inherent in the airflow-through scintillation cell method for radon measurement, this study introduces a compartmental model elucidating the behaviors of radon and its progeny within such cells. The computed results of the normalized equilibrium functions derived from the compartmental model, provide quantitative insights into the equilibrium progression of 222Rn and its progeny over time, substantiating the identified time-resolution limitation of 2-3hours. Laboratory experiments confirm the efficacy of the proposed correction algorithm, showcasing its ability to surmount the time-resolution limitation and achieve a rapid response in radon measurement using airflow-through scintillation cells.

Development of a novel low-pressure scintillation cell with ZnS(Ag)-coated clapboard for Rn-220 measurement

The high-precision measurement of Rn-220 is essential for assessing and preventing thoron radiological hazards. Prior research has revealed that employing a scintillation cell without a clapboard improves the detection efficiency for both Rn-222 and Rn-220 by reducing air pressure, and the Rn-220 calibration factor is established at an atmospheric pressure of 0.4. However, the decrease in air pressure leads to a corresponding reduction in Rn-220 concentrations within the scintillation cell, resulting in lower counts and larger statistical fluctuations. For the purpose of addressing this issue, a ZnS(Ag)-coated clapboard was added to the low-pressure scintillation cell for measuring Rn-222 and Rn-220. Several experiments were conducted in conjunction with Monte Carlo simulations. The results of these simulations, along with experiments using the standard radon chamber, provide valuable references for establishing the Rn-220 calibration factor. The experimental findings demonstrate that saturated detection efficiency of Rn-222 and Rn-220 can be maintained at below 0.7 atmospheric pressure. Therefore, the Rn-220 calibration factor, determined with the detection efficiency of 0.73 ± 0.04 at an atmospheric pressure of 0.7, was determined to be 31.98 ± 1.83 Bq·m−3·min−1 (k = 1).

Determining the calibration factor of Rn-220 by low-pressure scintillation cell

Accurately measuring Rn-220 is crucial for evaluating natural radiation exposure. For the large volume of normal scintillation cell, the detection efficiencies for different energy of α particles decayed from Rn-222, Rn-220 and their progeny are varied. To address this, two systems of the low-pressure scintillation cell were designed to make the shortest range of α particles with minimum energy decayed from Rn-222 longer than the longest distance between any two points in the scintillation cell by reducing air pressure. Thus, the detection efficiencies of the low-pressure scintillation cell for α particles decayed from Rn-222, Rn-220 and their progeny are same. The detection efficiency of low-pressure scintillation cell for α particles can be obtained by the standard radon chamber, and then the calibration factor of Rn-220 can be determined by low-pressure scintillation. Several verification experiments were performed. The experimental results show that the detection efficiencies of Rn-222 and Rn-220 at the air pressure of 0.4 P are very close and become saturated for lower values of air pressure. The calibration factor of Rn-220 calculated using the detection efficiency (0.76 ± 0.04) at the air pressure of 0.4 P is 53.75 Bq m−3 min−1 ± 2.96 Bq m−3 min−1 (k = 1).

Comparative study of radon sources and associated health risk in four underground uranium mines.

This paper presents a comparative study of the quantitative estimation of 222Rn and its health risk from various sources in four underground uranium mines. 222Rn exhalation rates from uranium-bearing rocks and backfill materials were estimated by calculating the 222Rn concentration accumulated in an enclosed chamber into which radon was exhaled. This comparative study indicates a more significant effect of porosity on the exhalation rates. Dissolved 222Rn in mine water was estimated using scintillation cell and bubbler kit. The discrepancy in 222Rn concentration in the mines might be attributed to the variation in geological features, ore grade, and porosity. This study revealed that the maximum radon exposure was produced from the backfill mill tailings, followed by uranium ore and mine water in the mines. The radon dose values in the individual mines remained under the safe dose limit of 20mSvyear-1. The excess lifetime cancer risk (ELCR) and 222Rn-induced lung cancer cases (RnLCC) per million persons per year were also estimated.

A compact neutron spectrometer system

A portable neutron spectrometer, nSpec, has been developed for passive interrogation of fast neutrons (> 1 MeV) from neutron sources. The design of the system includes four EJ-301 liquid scintillation cells, a custom stand, and tungsten caps for gamma-ray shielding. Data acquisition settings were optimized to provide a dynamic range of up to 15 MeV neutron energy. The detector response matrix was characterized using a time-of-flight method based on gamma-ray tagged neutron emission from 252Cf. The spectrum unfolding was characterized using measured and simulated spectra of AmBe and 252Cf with the GRAVEL and MLEM methods. Monte Carlo methods were used to examine the uncertainty propagation and determine sufficient counts for a measurement.

A CFD-based approach to optimize operating parameters of a flow-through scintillation cell for measurement of 220Rn in indoor environments.

The measurements and monitoring of 222Rn/220Rn have been of emerging interest in occupational environments particularly in radium/thorium handling facilities and environments with monazite deposits for the inhalation dosimetry. The performance of a flow-through Lucas scintillation cell (LSC) for long run 220Rn measurements, depends upon the exact distribution pattern of 220Rn and its decay products in the LSC which can vary with the design of inlet path and flow rates. In this work, the CFD technique has been used to study the concentration profiles of 220Rn and its decay products in LSC for varying flow rates and inlet needle lengths. The variation of alpha production efficiency (ηα) is computed and analyzed for each case; aiming to select the best operating range of parameters for the optimum performance of LSC for 220Rn measurements. It is seen that LSC can be operated in the flow rate ranging from 0.6 to 1 lpm with inlet needle length varying from 22.5 to 45 mm for improved sensitivity.

Radon gas build up using alpha scintillation cell: Experimentally and theoretically

Due to their high efficiency and speed of use, alpha scintillation cell is being increasingly utilized for detection of radon (222Rn) in soil gas. The calibration factor of the 110 A active radon cell has been addressed and thoroughly discussed. The sensitivity and the efficiency have been determined. It is found that the sensitivity and the registration efficiency of this scintillation cell (110 A active cell) are equal to 0.015895 cpm/Bq/m3, 59%. Respectively. A nuclear system was adapted to measure the accumulation of radon gas using the active scintillation cell. The growth curves of radon activity have been investigated. Radon emanation, leakage and back diffusion rates from natural occurring radioactive materials has been determined. Compatibility between practical measurements and results based on the theoretical equation were achieved.

Soil radon detection using active scintillation cell

ABSTRACT The paper herein is intended to present the registration efficiency of 300A alpha-scintillation active cell and its application in the field of soil radon detection. In this work, a radon chamber based on a natural radon source has been constructed. This chamber allows calibration of the active scintillation cell under flow-through condition. Radon source has been designed, constructed, and the radon concentration output has been measured. It has been observed that a steady radon concentration can be obtained inside the chamber after a period longer than 30 days. The steady radon concentration inside the chamber is equal to 123.58 Bq/m3. It is found that the registration efficiency and the sensitivity of the cell are equal to 0.69 and 1.243 CPM/pCi/l, respectively. After determining the calibration parameters of the cell, soil radon gas survey was carried out in the university city of Najran. It is found that the average radon activity concentration in the tested area is equal to 1332 ± 66 Bq/m3. Results of sensitivity and efficiency evaluation, along with radon measurements, are addressed and thoroughly discussed.

Detector Effects on the Response of a Highly Granular Hadron Calorimeter to Single Hadrons

In the detectors currently being developed for experiments on the next-generation lepton colliders, highly granular calorimeters are to be used. In particular, the hadron calorimeter is planned to be assembled from scintillation cells with direct readout of light by silicon photomultipliers. According to the results of experimental measurements of the light collection in a cell developed for the CALICE prototype hadron calorimeter, when detecting minimum ionizing particles, an estimate of the detector effects was obtained. The detector effect on the resolution of the ILD hadron calorimeter was studied by modeling the response of the detector to single neutral kaons. It was shown that the contribution of experimentally measured detector effects to the resolution for single particles is on the order of 0.5–1% in the range of hadron energy of 5–60 GeV.

Guidelines and Limits for the Quantification of Ra Isotopes and Related Radionuclides With the Radium Delayed Coincidence Counter (RaDeCC)

AbstractThe Radium Delayed Coincidence Counter (RaDeCC) is one of the most extensively used equipment for measuring 223Ra and 224Ra activities in water and sediment samples. Samples are placed in a closed He‐circulation system that carries the Rn produced by the decay of Ra to a scintillation cell. Each alpha decay recorded in the cell is routed to an electronic delayed coincidence system which enables the discrimination of 223Ra and 224Ra. In this study, the measurement and quantification methods using the RaDeCC system are assessed through analyses of registered data in different RaDeCC systems worldwide and a set of simulations. Results of this work indicate that the equations used to correct for 223Ra and 224Ra cross‐talk interferences are only valid for a given range of activities and ratios between isotopes. Above certain limits that are specified in this study, these corrections may significantly overestimate the quantification of 223Ra and 224Ra activities (up to ~40% and 30%, respectively), as well as the quantification of their parents 227Ac and 228Th. High activities of 226Ra may also produce an overestimation of 224Ra activities due to the buildup of 222Rn, especially when long measurements with low activities of 224Ra are performed. An improved method to quantify 226Ra activities from the buildup of 222Rn with the RaDeCC system is also developed in this study. Wethus provide a new set of guidelines for the appropriate quantification of 223Ra, 224Ra, 227Ac, 228Th, and 226Ra with the RaDeCC system.

A method for radiologically evaluating indoor use of dimension stone considering radon exhalation rates

Background: The use of natural radioactive building materials could be a health risk for both dwellers and mining workers. Therefore, a quick and effective method to test batches of rock samples is needed. Nevertheless, there is no reference value for maximum exhalation rates for building materials, except radiological hazard indices that do not measure gas exhalation rates directly. Objectives: This article investigated the correlations between Gamma Index and radon and thoron exhalation rates, and the proportions of radon and thoron in samples. Moreover, the main objectives were to analyze the feasibility of screening problematic samples for indoor use through a portable radiation detector (CoMo 170), which consists of a quick analysis at very low cost, and to simulate indoor concentration of radon using the measured exhalation rates of dimension stone slabs. Design: Best-selling dimension stone slabs were submitted to the following assays: gamma spectrometry, radon and thoron exhalation analysis using scintillation cell, and radioactivity measurement using a portable detector. Univariate and multivariate statistical analyses were conducted using Statistica 13 software. Results: The average activity concentrations measured were 971 ± 58.6 Bq/kg of 40K, 184 ± 9 Bq/kg of 232Th, and 74 ± 3 Bq/kg of 226Ra. The maximum activity concentrations of 40K, 232Th, and 226Ra series were 1,734 ± 100 Bq/kg, 2,667 ± 109 Bq/kg, and 596 ± 2 Bq/kg, respectively. The average exhalation rate of 222Rn was 406 ± 20 Bq/h m2. Conclusions: The main recommendations arising from this study are as follows: a portable radiation detector (CoMo 170) could be used as a screening method for selected samples; Gamma Index limit value = 1 for dimension stone slabs could be adopted when assessing radon and thoron exhalation; and the surface radon exhalation rate should be measured as a basis of recommendation for surface treatment before sales. Finally, thoron exhalations should be considered in radiological assessment, as 57% of the samples had higher thoron exhalation rates than radon.

Mass exhalation rates, emanation coefficients and enrichment pattern of radon, thoron in various grain size fractions of monazite rich beach placers

A study on exhalation rates of 222Rn and 220Rn and their enrichment pattern in different grain size fractions was carried out. Four different size fractions of the sand samples (1000-500 μm, 500-250 μm, 250-125 μm, and <125 μm) collected from the beach placers of south west coast of India were analysed for 226Ra and 232Th activity concentrations (Bq kg−1) by gamma spectrometry. Automated continuous measurement technique using scintillation cell based monitors were used to measure the 222Rn and 220Rn concentrations. These measured values were then fitted to appropriate model to extract the mass exhalation and emanation coefficients. The 222Rn mass exhalation rate varied from 0.7 ± 0.2 mBq kg−1 h−1 to 11.0 ± 0.9 mBq kg−1 h−1 while that of 220Rn varied from 88.5 ± 4.8 Bq kg−1 h−1 to 3066 ± 14 Bq kg−1 h−1. Higher mass exhalation rates, for both radioactive gases, were observed in finer grain size fractions. However, this was in contrast to the emanation coefficient values. Interestingly, higher radioactive monazite rich beach samples exhibited low emanation coefficient values compared to the low radioactive soil and sand samples reported in the literature. Statistical analysis showed a positive correlation, with correlation coefficient R = 0.84 and R = 0.79, respectively, between mass exhalation rates of 222Rn, 220Rn with their respective radioactive predecessors for different grain size fractions.

341. Radon mitigation: A practice example in medical clinics

Purpose Report the experience of Medical Physics Department of APSS Trento in coordinating the assessments and radioactive radon gas mitigations of medical clinics, complying with laws [1] , [2] . Methods and materials 42 measurement points were chosen in the workplaces at the lower floors (undergrounds, basements, ground floors) of the various buildings that were representative of the most critical situations with respect to aeration. Radon concentrations have been measured for one year through all workplaces using passive detectors, i.e. electrets giving integrated values, and also during Radon mitigation, using active detector, i.e. a Lucas scintillation cell monitor, allowing temporary monitoring. For each worker the effective dose was estimated applying the conversion factor 3·10−9 Sv·m3/Bq ·h [2] . Based on Radon concentration measurements and effective dose estimations, an evaluation of Radon mitigation has been undertaken (Fig. 1), adopting organizational or structural approach. Results The exceeding of the action levels [2] have been found only at medical clinics of Pinzolo and Levico, in terms of both concentration and effective dose. At Pinzolo a Radon concentration of 1745 Bq/m3 was measured, while at Levico it was found to be 1216 Bq/m3. Two different remedial actions were adopted. At Pinzolo an organizational approach was undertaken. Workers were transferred to another workplace at ground floor with a formwork for ventilated foundation, where the Radon concentration was 160 Bq/m3. Instead at Levico, considering also additional measurements in other places of the same building, an active soil depressurization through mechanical ventilation has been realized, leading to a Radon concentration less than 110 Bq/m3. The optimization of ventilation system was done using active dosimeters. Conclusion Although Radon mitigation is a challenging task, the adopted solutions proved to be effective.

Response of photomultiplier tubes to xenon scintillation light

We present the precision calibration of 35 Hamamatsu R11410-22 photomultiplier tubes (PMTs) with xenon scintillation light centred near 175 nm. This particular PMT variant was developed specifically for the LUX-ZEPLIN (LZ) dark matter experiment. A room-temperature xenon scintillation cell coupled to a vacuum cryostat was used to study the full-face PMT response at both room and low temperature ( ∼ −100 °C), in particular to determine the quantum efficiency (QE) and double photoelectron emission (DPE) probability in LZ operating conditions. For our sample with an average QE of (32.4 ± 2.9)% at room temperature, we find a relative improvement of (17.9 ± 5.2)% upon cooling (where uncertainty values refer to the sample standard deviation). The mean DPE probability in response to single vacuum ultraviolet (VUV) photons is (22.6 ± 2.0)% at low temperature; the DPE increase relative to room temperature, measured here for the first time, was (12.2 ± 3.9)%. Evidence of a small triple photoelectron emission probability ( ∼ 0.6%) has also been observed. Useful correlations are established between these parameters and the QE as measured by the manufacturer. The single VUV photon response is also measured for one ETEL D730/9829QB, a PMT with a more standard bialkali photocathode used in the ZEPLIN-III experiment, for which we obtained a cold DPE fraction of (9.1 ± 0.1)%. Hence, we confirm that this effect is not restricted to the low-temperature bialkali photocathode technology employed by Hamamatsu. This highlights the importance of considering this phenomenon in the interpretation of data from liquid xenon scintillation and electroluminescence detectors, and from many other optical measurements in this wavelength region.

Primary Standardization of 152Eu by 4πβ(LS) – γ (Nal) coincidence counting and CIEMAT-NIST method

The 4πβ-γ coincidence counting and CIEMAT/NIST liquid scintillation method were used in the standardization of a solution of 152Eu. In CIEMAT/NIST method, measurements were performed in a Liquid Scintillation Counter model Wallac 1414. In the 4πβ-γ coincidence counting, the solution was standardized using a coincidence method with ‘‘beta-efficiency extrapolation”. A simple 4πβ-γ coincidence system was used, with acrylic scintillation cell coupled to two coincident photomultipliers at 180° each other and NaI(Tl) detector. The activity concentrations obtained were 156.934 ± 0.722 and 157.403 ± 0.113 kBq/g, respectively, for CIEMAT/NIST and 4πβ-γ coincidence counting measurement methods.

Measurement of uranium and radon concentration in drinking water samples and assessment of ingestion dose to local population in Jalandhar district of Punjab, India

A study was conducted to assess the concentration of uranium and dissolved radon in drinking water samples collected from Jalandhar district of Punjab, India. The samples were analysed for dissolved radon using scintillation cell method. Laser fluorimetry was used for measurement of uranium concentration. Correlation analysis of radon and uranium concentrations and salinity and total dissolved solids with uranium was carried out. The uranium concentration in water samples varied from a minimum value of 1.53 ± 0.06 mg m−3 to 50.2 ± 0.08 mg m−3 with a geometric mean value of 14.85 mg m−3. The radon concentration in water varied from a minimum value of 0.34 ± 0.07 kBq m−3 to a maximum value of 3.84 ± 0.48 kBq m−3 with a geometric mean value of 1.46 kBq m−3. Ingestion dose to local population, due to radon and uranium in drinking water, for different age categories, was computed and results are being reported in this paper.

Electronic structure and optical properties of the scintillation material wurtzite ZnS(Ag)

In order to investigate the effect of Ag doping (ZnS(Ag)) and Zn vacancy ( $$V_\mathrm{{Zn}}$$ ) on the alpha particle detection performance of wurtzite (WZ) ZnS as a scintillation cell component, the electronic structure and optical properties of ZnS, ZnS(Ag), and $$V_\mathrm{{Zn}}$$ were studied by first-principle calculation based on the density functional theory. The results show that the band gaps of ZnS, ZnS(Ag), and $$V_\mathrm{{Zn}}$$ are 2.17, 1.79, and 2.37 eV, respectively. Both ZnS(Ag) and $$V_\mathrm{{Zn}}$$ enhance the absorption and reflection of the low energy photons. A specific energy, about 2.9 eV, leading to decrease of detection efficiency is observed. The results indicate that Ag doping has a complex effect on the detection performance. It is beneficial to produce more visible light photons than pure WZ ZnS when exposed to the same amount of radiation, while the increase of the absorption to visible light photons weakens the detection performance. Zn vacancy has negative effect on the detection performance. If we want to improve the detection performance of WZ ZnS, Ag doping will be a good way, but we should reduce the absorption to visible light photons and control the number of Zn vacancy rigorously.

Correcting for H2O interference using a RAD7 electrostatic collection-based silicon detector

The effect of water molecules on the electrostatic collection of 218Po ions onto the surface of silicon detectors (neutralization) is evaluated through the comparison with a scintillation cell (ZnS), not affected by air humidity. A radon monitor (RAD7, Durridge Company) was connected to a stainless steel radon chamber, equipped with the scintillation cell. Radon gas, extracted from an acidified RaCl2 source, was injected into the chamber and the amount of water molecules in the system was alternatively lowered or increased (from 0.00075 to 0.014 g of water in RAD7) by connecting the chamber to a desiccant or to a bubbling water bottle. The relative efficiency of the silicon detector with respect to the scintillation cell decreases with the growth of water molecules inside RAD7. This dependence, with a fixed i) electrostatic chamber geometry and ii) nominal high voltage, diverges during the humidification or the drying phase because it is in turn influenced by the length of interaction of polonium atoms with water molecules, which impacts on the size of 218Po clusters and thus on the neutralization process. For water contents higher that 0.01 g in RAD7, this effect is greatly enhanced. Temperature in the investigated range (18.5–35.6 °C) does not affect the efficiency of electrostatic collection-based silicon detectors.Based on these experiments, admitting a certain error on the efficiency (from 1.8 to 7.5%, depending on the water content), proper corrections were developed to adjust soil radon readings, when a desiccant is removed. This operation is necessary if recent Non-Aqueous Phase Liquids (NAPLs) leakage has occurred in the subsoil to avoid the sorption and possible later release of radon by Drierite, with related partition between the solid and liquid phases (water and NAPL).

An approach to discriminatively determine thoron and radon emanation rates for a granular material with a scintillation cell

A powder sandwich technique was applied to determine thoron (220Rn) and radon (222Rn) emanation rates for a granular material. The feature of this technique is the sample preparation, in which a granular material is put and fixed between two membrane filters. Airflow is directly given to this sandwich sample, will include thoron and radon emanated from the material, and then is transferred to the detector. This method makes sure that thoron and radon emanated are not retained in pore space within the sample volume, which is crucial for the appropriate emanation test. This technique was first introduced by Kanse et al. (2013) with the intention to measure the emanation of thoron - but not of radon - from materials having much higher 224Ra activity than 226Ra. In the present study, the methodology for the discriminative determination of thoron and radon emanation rates from a granular material has been examined using a flow-through scintillation cell and sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron- and radon-associated counts. With a sample of uranium ore, this model was experimentally validated by comparison between the scintillation cell and a reference detector that can discriminatively measure thoron and radon concentrations. Furthermore, the detection limits and uncertainties were evaluated to discuss the characteristics of this method. Key parameters for improving the determination of thoron and radon emanations were found to be the background radon concentration and the leakage of radon from the measurement system, respectively. It was concluded that the present method is advantageous to a sample that has much higher 226Ra activity than 224Ra.