Efficient Radiation Detectors Research Articles

Computational investigation of transport parameters of ions in gas-filled radiation detectors

In this study, a novel computational method was developed to investigate the transport characteristics of ions in gas-filled radiation detectors, which are closely linked to the behavior of ions in gaseous detectors. Parameters such as polarizability, mean free path, collision frequency, and mean free time, which directly impact ion mobility, were physically manipulated using the Monte Carlo technique, and the results were validated against fundamental physical principles. As an initial scenario, computations were performed on the mobility of Ar+ ions in an argon environment as a carrier gas. The distribution of the radial velocity components of the ion following an ion-gas collision was represented as a two-dimensional histogram with a disc-shaped pattern, and this result was elucidated utilizing the Maxwell-Boltzmann distribution. The findings regarding the mean free time and mean free path of an Ar+ ion in an argon carrier gas align with the results derived from Skullerud's methodologies. These findings hold promise for Garfield++ simulations, enabling the computation of ion mobility and even cluster ions in the mixture, thereby considering their impact on the detector's gain parameters. The results of this investigation offer novel insights into the behavior of ions within detector settings, significantly enhancing our comprehension of the mobility of ions and its effects on radiation detection efficiency.

Development of a phoswich detector utilizing bismuth germanate crystal scintillator and polyethylene naphthalate scintillation film

In this study, we present the development of a phoswich detector system employing a Bismuth Germanate (BGO) crystal scintillator in combination with a Polyethylene naphthalate (PEN) film plastic scintillator. Phoswich detectors can contribute to various applications, including radiation monitoring, medical imaging, and nuclear physics experiments, due to their ability to discriminate between different types of radiation. The thin PEN film is sensitive to α and β radiation, while the BGO scintillator exhibits good γ radiation detection efficiency. The incident radiation type and its energy can be determined by analyzing the difference in decay times between these two scintillators. This paper presents an analysis of the detector’s response to α, β, and γ radiation, and the particle tagging efficiencies are to be over 99.9%, 92%, and 99.8%, respectively.

Modeling and Bulk Characterization of 4HSIC Radiation Detector in Sentaurus TCAD Simulation Environment

This paper gives an insight into the need for radiation detection and the most commonly flexible and efficient radiation detector. It also examines bulk characteristics of 4H-SiC semiconductor radiation detector with Ni and Ti as metals for the contact. Bulk characterization of the device, including: doping concentration, electrons and holes behaviors, space charge and current densities were carried out. The modeling is conducted using Sentaurus Technology Computer Aided Design (TCAD) to examine charge transport in bulk 4HSiC material. Data obtained were further analyzed through Sentaurus visual, sentaurus Techplot and Excel to clearly determine the characteristics of the device. It is observed that when the semiconductor and metal are in contact, the Fermi-level is established where the doping concentration varied with either magnitude of the doping concentration or nature of the dopant. Similarly, Schottky and ohmic contacts and temperature effect were observed from the device characteristics which demonstrate that, the detector can withstand a temperature from the range of 100K to 700K in no fluctuating state.

Feasibility assessment of polycrystalline CsPbI3 relative dosimeters in photon and electron beam radiotherapy

Volumetric modulated arc therapy represents the latest technology in radiotherapy. It involves continuous modification of the multi-leaf collimator spatial distribution, dose rate, and gantry rotational speed, necessitating a dosimeter with high spatial resolution and exceptional sensitivity per unit volume. In particular, cesium-based inorganic perovskites have been studied for various applications, spanning from photoconductor solar cells to radiation detectors. These perovskites are renowned for their outstanding attributes, including thermal stability, inorganic stability, and light absorption capacity. Despite such advantageous characteristics, CsPbI3 materials have only been investigated in radiodiagnostics, with limited exploration in radiotherapy. To address this gap, this study verified the viability of CsPbI3 materials, note for their outstanding radiation detection efficiency, as dosimeters capable of measuring the radiation detection performance for radiotherapy devices. The reproducibility, linearity, and percent depth dose (PDD) were evaluated under the application of photon and electron beams in linear accelerators. The reproducibility assessment revealed impressive results, with the relative standard deviation registering at 0.53%, 0.32%, and 0.38% under electron beam energies of 6, 9, and 12 MeV and 0.45%, and 0.89% under photon beam energies of 6 and 15 MV. Moreover, the linearity test revealed an R 2 value of 0.9999, indicating high linearity, at 6, 9, and 12 MeV and at 6 and 15 MV. The PDD graphs drawn for the CsPbI3 dosimeter fabricated in this study showed that the D max points were consistent. The novel CsPbI3 dosimeter demonstrated a level of detection performance that satisfied all criteria; reproducibility, linearity, and PDD. The results collectively indicated that the CsPbI3 dosimeter can be used for dosimeters in radiotherapy devices.

The impact of strontium composition on thallium-doped cesium iodide scintillators

Investigating new scintillators with more alternative methods has been an attractive topic for a long time. This work aims to study the impact of strontium composition on thallium-doped cesium iodide scintillators. There are three different composition ratios of cesium iodide and strontium iodide precursors of 99:1, 95:5, and 90:10 with the same thallium doping of 0.28 mol%. The EDS measurements analyzed the soluble Sr-compositions in these grown crystals as 0%(undetectable), 0.43%, and 2.31%, respectively. With slightly increased strontium composition, the crystallite size was slightly smaller from 59.17, 45.51, to 33.23 nm, respectively. Moreover, the crystals have a somewhat more compressive strain and a slightly higher single crystallinity when the composition of strontium iodide increases. By analyzing the crystals' optical properties, the luminescent properties were trivially enhanced with a bit higher scintillation light yielding up to 29,859 photon/MeV of the crystal with a Sr-composition of 2.31%. Photoluminescence measurements exhibit the enhanced 520 nm scintillation and the lower 410 nm emission at higher Sr contents. These crystals’ emission decay times were obtained as τ1 = 500 ns (fast component) and τ2 = 700 ns (slow component) and slightly slower times with a higher Sr content. Lastly, radiation detection efficiency has been investigated at various energy levels of gamma rays from Am-241, Co-57, Ba-133, and Cs-137 sources. We found that the crystal with a higher Sr composition of 2.31% has better energy resolutions down to the best one of 7.9% at 662-keV measurement. In summary, higher strontium codoping with thallium in cesium iodide scintillators can enhance the crystal structure and optical properties. This would be one candidate of the promising scintillators for developing alternative high-performance radiation detectors for high-speed imaging applications.

Extreme γ-Ray Radiation Tolerance of Spectrometer-Grade CsPbBr3 Perovskite Detectors.

The perovskite compound CsPbBr3 has recently been discovered as a promising room-temperature semiconductor radiation detector, offering an inexpensive and easy-to-manufacture alternative to the current benchmark material Cd1-x Znx Te (CZT). The performance of CsPbBr3 sensors is evaluated under harsh conditions, such as high radiation doses often found in industrial settings and extreme radiation in space. Results show minimal degradation in detector performance after exposure to 1Mrad of Co-60 gamma radiation, with no significant change to energy resolution or hole mobility and lifetime. Additionally, many of the devices are still functional after being exposed to a 10Mrad dose over 3 days, and those that do not survive can still be refabricated into working detectors. These results suggest that the failure mode in these devices is likely related to the interface between the electrode and material and their reaction, or the electrode itself and not the material itself. Overall, the study suggests that CsPbBr3 has high potential as a reliable and efficient radiation detector in various applications, including those involving extreme fluxes and energies of gamma-ray radiation.

Портативная радиометрическая система, ее основные элементы и варианты применения

The paper discusses the main elements of the developed portable radiometric system (PRS) and options for its application. Silicon photomultipliers were used in the development of the PRS detector modules. It made possible to significantly reduce their size. Such devices and systems find their application in solving various problems of medical radionuclide diagnostics that require an increased field of view, an extended research time range and mobility. The main goal of the work was to find the optimal configuration of the PRS elements to ensure its minimum size and, at the same time, the maximum radiation detection efficiency, taking into account the features of the objects under study and the kinetics of the processes occurring in them. In addition, an algorithm for selecting the minimum amount of activity of a radioactive preparation required for each study is additionally considered.

Improvement in Plastic Scintillator with Loading of BaFBr:Eu²⁺ Radioluminescence Phosphor

This article describes a new concept of developing a composite plastic scintillator (PS) with better light out and detection efficiency of ionizing radiations by loading high Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> radioluminescence (RL) phosphor powder. Gamma-ray interaction in PSs has been enhanced due to increased photoelectric absorption in the loaded BaFBr:Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> phosphor powder. RL BaFBr:Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> powder has been synthesized by a high-temperature solid-state diffusion method in reducing atmosphere. Polystyrene-based PS sheets of 250±50 μm thickness have been prepared with 2.5-diphenyl oxazole (PPO) and 1.4-bis(5-phenyl-2-oxazolyl) benzene (POPOP) as primary and secondary fluors, respectively, mixed with the synthesized phosphor powder in different weight percentages. Radiation detection properties of the composite PS have been studied for alpha, beta, neutron, and gamma radiations of different energies. The composite PS sheet loaded with 20 wt% of phosphor powder showed maximum intensity for RL and photoluminescence (PL). Studies also confirmed a significant increase in the radiation detection efficiency in composite PS for various energies of beta and gamma rays. The lifetime measurement of the composite PS showed same nanosecond lifetime which is appropriate for fast counting and matches closely with the PS without loading. Pulse height analysis for various ionizing radiations of different energies confirmed significant improvement in the detection efficiency of loaded PSs.

Extreme Radiation Sensitivity of Ultra-Low Loss Pure-Silica-Core Optical Fibers at Low Dose Levels and Infrared Wavelengths.

We report here the response of a commercial ultra-low loss (ULL) single-mode (SM) pure silica core (PSC) fiber, the Vascade EX1000 fiber from Corning, associated with 0.16 dB/km losses at 1.55 µm to 40 keV X-rays at room temperature. Today, among all fiber types, the PSC or F-doped ones have been demonstrated to be the most tolerant to the radiation induced attenuation (RIA) phenomenon and are usually used to design radiation-hardened data links or fiber-based point or distributed sensors. The here investigated ULL-PSC showed, instead, surprisingly high RIA levels of ~3000 dB/km at 1310 nm and ~2000 dB/km at 1550 nm at a limited dose of 2 kGy(SiO2), exceeding the RIA measured in the P-doped SM fibers used for dosimetry for doses of ~500 Gy. Moreover, its RIA increased as a function of the dose with a saturation tendency at larger doses and quickly recovered after irradiation. Our study on the silica structure suggests that the very specific manufacturing process of the ULL-PSC fibers applied to reduce their intrinsic attenuation makes them highly vulnerable to radiations even at low doses. From the application point of view, this fiber cannot be used for data transfer or sensing in harsh environments, except as a very efficient radiation detector or beam monitor.

A position sensitive scintillation detector using a side-by-side GAGG-F/GAGG-T phoswich block

Position sensitive detectors are the key component of gamma-ray imaging systems such as coded-aperture cameras and emission computed tomography systems. Improving the intrinsic spatial resolution of detectors is critical to system performances. Recent advance of the GAGG scintillator production allows variable decay time with different Al/Ga ratios. In this paper, we developed a novel position sensitive scintillation detector using a side-by-side fast\ obreakdash-GAGG/typical-GAGG (GAGG-F/GAGG-T) phoswich array, which consisting of 12×12 phoswich unit pairs assembled by the GAGG-F scintillator (decay time constant ∼ 50 ns) and the GAGG-T scintillator (decay time constant ∼ 90 ns) in a pixel size of 1.35×2.7×4 mm3 and coupled to a 8×8 SiPM (MicroFJ\ obreakdash-30035\ obreakdash-TSV) array. An experiment was conducted using the irradiation of a 57Co source (122 keV) . Experimental results demonstrate that events from the GAGG\ obreakdash-F and GAGG-T scintillators can be discriminated with only 7% mis-assignment probability. The 12×12 of GAGG\ obreakdash-F and GAGG-T scintillator arrays are both distinguishable in separated flood maps. The average energy resolutions of GAGG\ obreakdash-F and GAGG-T scintillators at 122 keV are 27.58% and 23.51% respectively. The side-by-side GAGG-F/GAGG-T detector has the advantage of improved intrinsic spatial resolution, no intrinsic background radiation and uniform detection efficiency.

Tuning the decay time of plastic scintillators

In the field of nuclear physics, plastic scintillators are popular and efficient radiation detectors thanks to the following properties: they can be prepared in large volumes, are cheap and various configurations can be afforded to the material. However, peculiar applications might require plastic scintillator with unusual scintillation decay times, such as laser beam positioning or detectors stacking. In the case of the scintillation decay time, commercial suppliers do not propose many choices, as only the range 0.7–10 ns is usually covered, along with a longer decay time – 285 ns – material. Herein we propose a new concept and associated formulations where the scintillation decay time can be finely chosen and tuned in a range starting at 2.5 ns and finishing around 90 ns. These materials are presented, synthesized and characterized.

Zero-dimensional Cs4EuX6 (X = Br, I) all-inorganic perovskite single crystals for gamma-ray spectroscopy

The zero-dimensional all-inorganic perovskites are self-activated blue emitters with slight hygroscopicity, scalable synthesis, and high radiation detection efficiency.

Development and Comparison of Fiber-Optic Beta Radiation Sensors with Different Diameters of Their Sensing Probes

A fiber-optic radiation sensor (FORS) was developed for remote and real-time measurements of beta radiation from radioactive-contaminated soil. The sensing probe consisted of a bundle of organic scintillators and a mixture of epoxy resin to improve the detection efficiency. The measurement system consisted of a sensing probe with an aluminium foil reflector, a transmitting plastic optical fiber, and a light-measuring system comprising a photomultiplier tube, a preamplifier, a multichannel analyzer, and a laptop computer. Several sensing probes, whose dead-end diameters were 26 mm (bundle type I), 36 mm (bundle type II), and 46 mm (bundle type III), were prepared and characterized to identify the best sensing probe in terms of its radiation detection efficiency. The reproducibility of the FORS for the measurement of beta radiation was confirmed using a χ2-test. The measurements showed that the FORS sensing probe with a diameter 46 mm has the best detection performance.

Impact of precursor purity on optical properties and radiation detection of CsI:Tl scintillators

Cesium iodide doped with thallium (CsI:Tl) crystals was grown to develop the gamma-ray detectors by using low-cost raw materials. Effect of impurities on optical properties and radiation detection performance was investigated. By a modified homemade Bridgman–Stockbarger technique, CsI:Tl samples were grown in two levels of CsI and TlI reactant materials, i.e., having as a very high purity of 99.999 % and a high purity of 99.9 %. XRD measurements indicate CsI:Tl crystals having a good quality with a dominant (110) plane. Having a cubic structure, a lattice constant of CsI crystals of 0.4574 nm and a crystallite size of 43.539 nm were obtained. From the lower-purity raw materials, calcite was found in an orange crystal with a lattice constant of 0.4560 nm and a crystallite size of 43.089 nm. By PL measurements, the optical properties of the CsI:Tl crystals were analyzed. ~540-nm-wavelength PL peak was observed from the colorless high-purity crystal, and ~600-nm-wavelength PL peak was observed from the orange crystal. The brighter PL emission was obtained from the orange crystals suggesting impurities. CsI:Tl surface morphology by SEM exhibited a smooth surface with some parallel crystal facets. For electrical properties of high-quality CsI:Tl crystals, the electrical resistances were 230 ± 16 MΩ in cross-sectional direction and 714 ± 136 MΩ in vertical direction with respect to more homogeneous crystal quality in cross-sectional direction than that in vertical direction. TEM measurement was applied to evaluate the microstructure of colorless CsI:Tl crystal with different patterns of a cubic structure. Both CsI:Tl crystals show good efficiencies and good resolutions. Maintaining the same electronic conditions and amplifications, the colorless CsI:Tl scintillators represented a higher detection efficiency at 122 keV of Co-57 of 78.4 % and the energy resolution of 23.3 % compared to the detection efficiency of 75.9 % and the energy resolution of 34.6 % of the orange scintillators. In summary, the unintended impurity as calcite in low-cost CsI:Tl scintillators was found to enhance PL emission but shift the PL wavelength. However, efficiency of radiation detection is slightly lower. By coupling with a suitable PMT, the radiation detection efficiency of low-cost CsI:Tl scintillators can be improved. From these valuable results, growing new ternary materials as CsCaI2 or CsI:Ca or Ca-codoped CsI:Tl scintillators could be one of the promising approaches to achieve highly efficient and low-cost radiation detectors with the optimization of the crystal growth conditions in the future.

Tackling Single Crystal Growth Challenges for Mixed-Elpasolite Scintillators

The rising demand for efficient radiation detectors in various applications has led to intense research on single crystal scintillators. The scintillation performance strongly depends on the as-grown crystal quality. Mixed-anion elpasolite single crystals with Ce-doping such as Cs2NaREBr3I3 (RE = La, Y) are among the most promising candidates as next generation scintillators. However, there are multiple challenges to traditional single crystal synthesis using melt–freeze growth techniques due to the complicated composition, as well as impurities, and varying thermal behavior of the starting materials. To improve the as-grown single crystal quality and optimize their scintillation properties, a series of investigations on material treatment and synthesis, ampule design, and crystal growth parameters were conducted. Effective purification of the carbon- and oxygen-based impurities improved the optical transmittance of the crystal. Differential scanning calorimetry and thermal gravimetric analysis results re...

Influence of preparation parameters on the synthesis of plastic scintillation microspheres and evaluation of sample preparation

Plastic scintillation microspheres (PSm) are solid dispersions of fluorescent solutes encapsulated in a polymeric matrix; they are used to measure β and α decay of radionuclides. Since organic solvent evaporation/extraction methods have been successfully employed to produce PSm, this work evaluates the influence of different parameters (i.e., polystyrene (PS) and polyvinyl alcohol (PVA) concentrations, temperature, stirring speed and the organic/aqueous phase ratio) on the final size of the PSm; and the relationship between this final size and the radiometric capacities of the PSm in relation to emitters of both beta (3H, 14C and 90Sr/90Y) and alpha (241Am) radiation.The results show that when the concentration of PVA is increased, the size of the PSm decreases; meanwhile, an important decrease in particle size is also achieved when the PS concentration is decreased. For almost all the parameters evaluated, the resultant PSm were smoothed and spherical. However, when temperature was increased, the particle size increased and the PSm eventually became amorphous and porous. The observed decrease in particle size correlated with an increase in radiation detection efficiency and a movement in the positioning of the spectra at lower energy values.We also evaluated the reproducibility of the vial preparation for 3H measurements and confirmed that small variations in the quantity of PSm and preparation of different vials by different experimenters did not influence the radiometric capacities.

Performance analysis of PIN photodiode under gamma radiation effects through modeling

The main objective of this paper is to evaluate the p-i-n photodiode as a radiation detector for gamma ray spectroscopy. Therefore, the effect of incident gamma radiation on p-i-n photodiode performance characteristics is evaluated. The p-i-n photodiode is interesting from the point of view because it has numerous advantages over conventional semiconductor junction in terms of better long wavelength response, radiation hardness, high quantum efficiency, long lifetime and lower cost. Therefore, it is important to analyze and evaluate their characteristics. Models for this interesting type of detector were developed. These models describe a nontrivial evaluation of the most important characteristics. The minority carrier of the holes of the developed model is obtained by self-consistently solving the one-dimension diffusion equation. On other hand, it is used to calculate the diffusion length, diffusion current, drift current, total current, quantum efficiency and signals-to-noise ratio (SNR) as a function of the structural parameters. These parameters are the radiation fluence, photodiode area, bias voltage, spectral wavelength and the operating temperature. Also, optimization of various characteristics of p-i-n photodiode is of primary concern. A comparison between the results obtained by proposed models and that published are conducted and full agreement is observed. Therefore, it confirms our models and their validity on practical applications. The main strength of p-i-n photodiodes is that the gap between induced diffusion current and drift current is large. Moreover, the p-i-n photodiode has a comparable value of SNR accomplished with low values of corresponding bias voltage. The obtained results assure that p-i-n can be used as an efficient radiation detector.

A theoretical study of CsI:Tl columnar scintillator image quality parameters by analytical modeling

Medical X-ray digital imaging systems such as mammography, radiography and computed tomography (CT), are composed from efficient radiation detectors, which can transform the X-rays to electron signal. Scintillators are materials that emit light when excited by X-rays and incorporated in X-ray medical imaging detectors. Columnar scintillator, like CsI:T1 is very often used for X-ray detection due to its higher performance. The columnar form limits the lateral spread of the optical photons to the scintillator output, thus it demonstrates superior spatial resolution compared to granular scintillators. The aim of this work is to provide an analytical model for calculating the MTF, the DQE and the emission efficiency of a columnar scintillator. The model parameters were validated against published Monte Carlo data. The model was able to predict the overall performance of CsI:Tl scintillators and suggested an optimum thickness of 300μm for radiography applications.

Development of polymerizable 2-(1-naphthyl)-5-phenyloxazole scintillators for ionizing radiation detection

Fluor monomers synthesized, characterized, and then polymerized into high β radiation detection efficiency extractive scintillator.

Novel Approach to Surface Processing for Improving the Efficiency of CdZnTe Detectors

We emphasize an improvement of the surface processing procedures for cadmium zinc telluride (CZT) detectors, which is one of the principal problems limiting the technology. A rough surface enhances the leakage current into the medium, creating additional trapping centers and thereby degrading the detector’s performance. Mechanical polishing followed by chemical treatment yields smoother surfaces as required, but chemical treatment, especially with bromine-based solutions, induces unwanted surface features, increases the surface conductivity, and generates chemical species that alter the material’s surface and interfacial properties. It is essential to avoid such adverse consequences of surface etching in the manufacturing of highly efficient radiation detectors. We approached the problem of processing the crystals’ surfaces by using two different solutions (a low-concentration bromine-based etchant mixture in conjunction with a surface-passivation reagent and a non-bromine-based etchant). The chemomechanical treatment yielded smooth nonconductive surfaces with fewer detrimental features, therefore allowing us to fabricate better devices. We determined the surface roughness using atomic force microscopy and optical profilometry (OP). We analyzed the surface structure, orientations of the crystals, and formation of chemical species by x-ray photoelectron spectroscopy techniques and delineated their effects on the devices’ electrical properties and performance. Our experimental data revealed that our new chemical etching process produced nonconductive surfaces with fewer surface defects and so improved the detectors’ charge transport and efficiency. We detail the results of our new etchants and compare them with those for conventional Br-methanol etchants.