Solid-state Detectors Research Articles

The physical mechanisms of neutron detection

ABSTRACT Neutrons do not directly ionise the medium they pass through, unlike charged particles. Neutron detection is then based on nuclear reactions in which the neutron is typically lost and charged particles and/or γ-rays are generated in the final state. These are subsequently detected by appropriate sensors of various types, such as gas, scintillation, and solid-state detectors. Neutrons generated at large scale facilities (fission reactors or accelerator-driven plants) typically cover a very wide energy range. The nuclear reactions that are found to be effective at different energies make neutron detection on the one hand complex from an instrumental point of view, and on the other hand interesting from the point of view of the physics underlying the approach to be used. This article aims at presenting and discussing the main features of the nuclear reactions of interest in neutron detection in different energy ranges, and the physical processes that take place in typical sensors used as detection tools. This approach is intended to describe the entire physical process, from neutron-nucleus interaction to the physical sensor response, that represents the detection event.

Dark matter searches and energy accumulation and release in materials

Efforts to identify dark matter by detecting nuclear recoils produced by dark matter particles reveal low-energy backgrounds of unknown origin in different types of detectors. In many cases, energy accumulation and delayed burst-like releases of stored energy could provide an explanation. These dynamics follow Prigogine’s ideas on systems with energy flow and the general Self-Organized Criticality scenario. We compare these models with properties of excess backgrounds in cryogenic solid-state detectors, relaxation processes in glasses and crystals, our observations of delayed luminescence in NaI(Tl), and make predictions for more phenomena present in these systems and in superconducting photon detectors and qubits. Experiments to create accurate phenomenological models are needed.

Performance of a Ge-doped optical fibre dosimeter for CT real-time measurements

This study investigates the dosimetric characteristics of a real-time radioluminescence (RL) Ge-doped optical fiber sensor, model LS-1000, providing measurement of absorbed dose in terms of counts in use of a computed tomography (CT) system. A CT dose index head phantom has been used as the reference tool. The response of the LS-1000 sensor has been compared against that of two other forms of dosimeter - a RaySafe X2 CT sensor (an ionization chamber system) and a Black Piranha CT dose profiler (a point dose solid-state detector). The three dosimeters have been irradiated in each of five available holes within the CT dose index head phantom. The results show RL response at the position of the peripheral holes of around 250 counts/gate for a gate time of 10 ms, while at the position of the central hole the response was 80 counts/gate. The maximum dose rate for the RaySafe X2 CT sensor has been found to be 5 mGy/s while that observed for the CT dose profiler was 6 mGy/s. In respect of CT applications, this trial of the luminescence device demonstrates that the germanium-doped optical fiber device may offer a promising alternative to conventional dosimeters, also allowing measurements at high accuracy and precision.

Mapping of Alpha Emitters for Soil Samples in Kufa Districts, Iraq

Abstract: In this study, radon (Rn) gas concentrations were measured in the soil samples taken at various locations in the Kufa district, Iraq. The study was conducted using a solid-state nuclear track detector (SSNTD), commercially known as CR-39, purchased from the TASTRAK Analysis System. Also, radium and uranium concentrations and annual effective dose, mass exhalation rate, surface exhalation rate, and excess lifetime cancer risk due to radon gas were calculated. The results show that the average values, with a standard deviation of radon concentrations, in the air space of a tube containing the sample and in the samples were 14±1 Bq/m3 and 895±74 Bq/m3, respectively. We also found that the average value of the annual effective dose was 0.36±0.08 mSv/y. We employed the GIS (ArcGIS 10.7.1.) technique to draw the main conclusions of the study. The study demonstrates that the measured levels of radon gas concentrations are within acceptable ranges in terms of potential health risks. Keywords: Alpha emitters, Radon gas, Soil, GIS, Kufa district, Radiation maps.

DETERMINATION OF URANIUM CONCENTRATIONS IN RICE SAMPLES AVAILABLE IN THE IRAQI MARKET USING THE CR-39 DETECTOR

In this study, the results of the uranium concentrations and specific activity in 10 rice samples are described using a solid-state track detector (CR-39). Samples were collected from various local Iraqi markets with different origins (Iraq, India, America, and Thailand). Our findings found that the results of uranium concentration in all studied samples are ranging from (0.55 ± 0.28 to 1.74 ± 0.31) ppm with a weighted average of (1.24 ± 0.99) ppm. Also, results demonstrate that the specific activity values of the studied samples swing between values of (6.88 ± 3.52 and 21.49 ± 3.85) Bq/Kg. The obtained results of the studied rice samples are indicated that it is less than the acceptable limit of those studies established by many organizations such as the United Nations scientific committee on the effects of atomic radiation (UNSCEAR), the international atomic energy agency (IAEA), the world health organization (WHO), and others.

Exploring the impact of incoherent Compton scattering on X-ray pair distribution function analysis of disordered materials

X-ray atomic pair distribution function (XPDF) measurements using a two-dimensional area detector have been of great value in studying atomic structures of materials with varying degrees of disorder. However, an area detector does not have energy resolution. Thus, incoherent inelastic Compton scattering and fluorescence are not discriminated, contaminating coherent elastic scattering. This paper investigates the effects of random noise from incoherent scattering on XPDF analysis. To conduct the study, the elastic scattering, Compton scattering and fluorescence of In0.33Ga0.67As alloy were separately measured using an intrinsic Ge solid-state detector with energy resolution. It is found that the addition of Compton scattering with a noise-to-signal ratio of about 0.8% results in the smearing of diffuse scattering in the high-Q region. Moreover, adding extra noise from fluorescence increases the smearing, overwhelming the diffuse scattering. Additionally, simulated data of elastic and Compton scattering on ferroelectric Ba(Ti0.8Zr0.2)O3 were used to investigate the evolution of noise fluctuation and its effects on the XPDF as a function of total intensity.

How Fast is Your Detector? The Effect of Temporal Response on Image Quality.

With increasing interest in high-speed imaging, there should be an increased interest in the response times of our scanning transmission electron microscope detectors. Previous works have highlighted and contrasted the performance of various detectors for quantitative compositional or structural studies, but here, we shift the focus to detector temporal response, and the effect this has on captured images. The rise and decay times of eight detectors' single-electron response are reported, as well as measurements of their flatness, roundness, smoothness, and ellipticity. We develop and apply a methodology for incorporating the temporal detector response into simulations, showing that a loss of resolution is apparent in both the images and their Fourier transforms. We conclude that the solid-state detector outperforms the photomultiplier tube-based detectors in all areas bar a slightly less elliptical central hole and is likely the best detector to use for the majority of applications. However, using the tools introduced here, we encourage users to effectively evaluate which detector is most suitable for their experimental needs.

Visible Radiophotoluminescence of Color Centers in Lithium Fluoride Thin Films for High Spatial Resolution Imaging Detectors for Hard X-rays

Passive solid-state detectors based on the visible radiophotoluminescence (RPL) of stable aggregate F2 and F3 + color centers in lithium fluoride (LiF) are successfully used for X-ray imaging and advanced diagnostics of intense X-rays sources. Among their advantages, these detectors offer a wide dynamic range and simplicity of use. They can be read non-destructively using a fluorescence microscope, enabling high spatial resolution over a large field of view. Optically transparent LiF films, of three different increasing thicknesses, were grown by thermal evaporation on glass and silicon substrates and subsequently irradiated with monochromatic 7 keV X-rays at several doses from 1.3 × 101 to 4.5 × 103 Gy at the SOLEIL synchrotron facility. For all the LiF films, the RPL response was found to depend linearly on the irradiation dose, with films grown on Si(100) substrates exhibiting up to a 50% higher response compared to those grown on glass. A minimum dose of 13 Gy was detected, despite the low thickness of the irradiated films. The limited thickness of the homogeneously colored LiF film allowed to obtain a spatial resolution of (0.44 ± 0.04) μm in edge-enhancement imaging experiments conducted by placing an Au mesh in front of the samples.

Energy-based Hp(3) measurement using solid-state detector.

This study aimed to develop an energy-based Hp(3) measurement method using a solid-state detector (SSD). Incident and entrance surface air kerma were measured using an ionization chamber placed free-in-air and in front of an anthropomorphic or slab phantom. Subsequently, three SSDs were placed free-in-air, and half-value layer and readings were obtained. After measurements, an X-ray beam quality correction factor $\left ({{k}}_{{Q},{{Q}}_{\mathbf{0}}}^{{SSD}}\right)$, backscatter factor (BSF) and conversion factor from incident air kerma to Hp(3) (C3) were determined. Then, the incident air kerma by SSD $\left ({{K}}_{{a},{i}}^{{SSD}}\right )$, Hp(3) and Hp(3)/${{K}}_{{a},{i}}^{{SSD}}$ were calculated. The ${{k}}_{{Q},{{Q}}_{\mathbf{0}}}^{{SSD}}$ was almost consistent for all SSDs. The C3 and BSF were found to increase as tube potential increased. The Hp(3)/${{K}}_{{a},{i}}^{{SSD}}$ calculated with the anthropomorphic and slab phantoms were consistent within 2.1% and 2.6% for all SSDs, respectively. This method improves the energy dependence of Hp(3) measurement and can estimate the Hp(3) measurement error for dedicated Hp(3) dosemeters.

Impact on dosimetry of occupationally exposed individuals on the patient management for PET/MRI studies: a comparison study with dosimetry on PET/CT

PET/MRI technology has expanded the boundaries of investigation in nuclear medicine, supported by the high sensitivity of solid-state PET detectors. Nonetheless, the coil positioning might lead to an increased exposure period of the worker to the injected patient. This procedure does not occur on PET/CT and, therefore, exposure period is reduced on such scanner. The aim of our study was to evaluate the dosimetry of two occupationally exposed individuals (OEI) working at the Center of Nuclear Medicine of Hospital das Clínicas of the University of Sao Paulo. We used thermoluminescent (TLD) dosimeters in pulse, whole-body and crystalline for PET/MRI and PET/CT procedures during five months of clinical and research routine. We also monitored the time for positioning/removing the patient on both scanners. For this study, OEI1 performed 76 PET/MRI studies and 102 PET/CT studies while OEI2 performed 26 and 56 PET/MRI and PET/CT studies, respectively. We found no evidence of differences for the whole-body dose values between both scanners (p = 0.22). The average time of patient management (positioning/removing the patient) was 14.38, and 3.81 minutes for PET/MRI and PET/CT, respectively. When the normalization by the number of PET/CT studies was applied, we found no statistical difference for effective and equivalent dose values. Our study encourages future investigations on nursing staff, which is a critical population that is exposed to ionizing radiation, mainly on dynamic studies, due to the synchronized injection with the protocol starting.

Nature of radon, radium, exhalation and uranium concentration from construction materials used in Al Jouf city, Saudi Arabia

This study aims to assess seven group samples used as building materials in the Saudi Arabian market in Al Jouf city had their radon concentration, exhalation rate, radium activity, as well as the risk of death due to cancer in excess of the natural background risk due to exposure to carcinogens over a period of a lifetime (Excess Lifetime Cancer Risk), and uranium content measured. The ‘Can technique’ was employed, which is based on the use of Solid State Nuclear Track Detectors (SSNTDs) CR-39. The average level of radon concentrations (Bq/m3) for the materials under investigation are as follows: 99.40 ± 10.26 (Soil), 146.92 ± 12.49 (Cement), 115.68 ± 11.13 (Gypsum), 132.28 ± 11.89 (Ceramic), 223.24 ± 14.8 (Marble), 210.85 ± 14.72 (Bricks), and 241.71 ± 15.65(Gravel) at Bq. m-3. The results indicate that radon levels in Soil, Cement, Gypsum, and Ceramics are below the allowed limit of exposure to radon for humans, set at 200 Bq. m−3, while in the cases of Marble, Bricks and Gravels, have been higher than the allowed limit. Results for Annual Effective Dose came in as follows: Soil = 2.09 mSv/y; Cement = 3.09 mSv/y; Gypsum = 2.43 mSv/y; Ceramic = 2.78 mSv/y; Marble = 4.69 mSv/y; Bricks = 4.43 mSv/y and finally, Gravel = 5.08 mSv/y. These measurements were higher than the global average (1 mSv/y). The average annual cancer risk of the samples measured, were as follows: 8.05 (Soil); 11.89 (Cement); 9.36 (Gypsum); 10.71 (Ceramic); 18.07 (Marble); 17.07 (Bricks) and finally, 19.56 (Gravel). The average mass exhalation rates and surface exhalation for the materials under investigation are as follows: (0.08 Bq kg−1h−1 – 3.95 Bq m−2 d−1) for (Soil), (0.18 Bq kg−1h−1 – 5.85 Bq m−2 d−1) for Cement, (0.20 Bq kg−1h−1– 4.60 Bq m−2 d−1) for Gypsum, (0.08 Bq kg−1h−1– 4.26 Bq m−2 d−1) for Ceramic, (0.19 Bq kg−1h−1– 8.88 Bq m−2 d−1) for Marble, (0.18 Bq kg−1h−1– 8.39 Bq m−2 d−1) for Bricks and (0.18 Bq kg−1h−1– 9.62 Bq m−2 d−1) for Gravel. The mean estimated values for the radium activity were 30.6 ± 3.18 Bqkg−1 (Soil); 67.6 ± 5.66 Bqkg−1 (Cement); 73.9 ± 6.99 Bqkg−1 (Gypsum); 47.8 ± 4.20 Bqkg−1 (Ceramic); 70.1 ± 4.57 Bqkg−1 (Marble); 66.8 ± 4.7 Bqkg−1 (Bricks) and 67.4 ± 4.40 Bqkg−1 (Gravel). From a health hazard viewpoint, the results showed that the samples under review are safe and are not life-threatening. The mean estimated values for the uranium content are as follows: 1.35 ppm (Soil); 2.98 ppm (Cement); 3.26 ppm (Gypsum); 2.11 ppm (Ceramic); 3.09 ppm (Marble); 2.94 ppm (Bricks) and 2.97 ppm (Gravel).

An Innovative Method for Mitigation of Radon: A Case Study in Bangalore Area, Karnataka, India

Introduction:
 Elevated radon levels in the indoor environment in many countries that led to the realization of residential radon as being a possible public health issue in the western world. It was also hoped that in conjunction with epidemiological studies, large-scale indoor radon surveys might lead to quantitative understanding of the low dose effects of radon exposures. Earlier work for the environment of Bangalore city reveals that, the activity concentrations of 226Ra in soil varied in the range of 7.7–111.6 Bqkg-1 with a mean value of 26.2 Bqkg-1. The concentration of 232Th varied in the range 16.7–98.7 Bqkg-1 with a mean value of 53.1 Bqkg-1 and that of 40K in the range 151.8 –1424.2 Bqkg-1 with a mean value of 635.1 Bqkg-1. An attempt has been made to observe the reduction in radon concentration by deploying lamination on the walls and mosaic tiles on the floorings of the room.
 Objectives: Radon mitigation is a new approach to minimize the radioactive gases in the working environment. In view of this an attempt has been made to witness the reduction in radon concentrations due to Formica laminate on the walls and placing mosaic tiles on the flooring of the room. 
 Methods: CAN technique and solid state nuclear track detectors based dosimeters are used for the observation of radon exhalation and the concentration of radon/thoron levels in a room. .
 Results: Good reduction in radon levels were observed after deploying the Formica laminate on the walls of the room and the mosaic on the floorings of the room. This is an innovative method needs to be incorporated for the reduction in higher level concentrations. 
 Conclusions: Reduction in concentration is more than 50% after renovation and it may be used as an innovative approach.

Robust Thermal Neutron Detection by LiInP2 Se6 Bulk Single Crystals.

Direct neutron detection based on semiconductor crystals holds promise to transform current neutron detector technologies and further boosts their widespread applications. It is, however, long impeded by the dearth of suitable materials in the form of sizeable bulk crystals. Here, we have developed high-quality centimeter-sized LiInP2 Se6 single crystals using the Bridgman method and systematically investigated their structure and property characteristics. The prototype detectors fabricated from the crystals demonstrate an energy resolution of 53.7% in response to α-particles generated from an 241 Am source and robust, well-defined response spectra to thermal neutrons that exhibit no polarization or degradation effects under prolonged neutron/γ-ray irradiation. We have also identified the primary mechanisms of Se-vacancy and InLi antisite defects in the carrier trapping process. Such insights are critical for further enhancing the energy resolution of LiInP2 Se6 bulk crystals towards the intrinsic level (∼8.6% as indicated by our chemical vapor transport-grown thin crystals). These results pave the way for practically adopting LiInP2 Se6 single crystals in new-generation solid-state neutron detectors. This article is protected by copyright. All rights reserved.

Evaluation of indoor 222Rn and 220Rn concentrations in Dakshina Kannada, Karnataka, India

Naturally occurring radioactive gases which tend to build up (radon and thoron) in indoor environs can cause deleterious health effects including the development of lung cancer. The present study aims to measure 222Rn and 220Rn levels in dwellings in different seasons in the environs of Dakshina Kannada region of India. The 222Rn and 220Rn concentrations were measured in the monsoon, autumn, winter, and summer seasons using Solid State Nuclear Track Detector (SSNTD, LR-115 type II) films fixed in single-entry pinhole cylindrical twin-cup dosimeters. The higher 222Rn levels in indoors were observed during winter with an average concentration of 38.8Bqm-3 and lower during summer with an average of 14.1Bqm-3. The average indoor thoron concentration was also highest in winter with an average value of 25.5Bqm-3 and lowest in summer with 8.8Bqm-3. The annual inhalation dose ranged from 0.44 to 1.06mSvyear-1 with a mean value of 0.66mSvyear-1. The annual effective dose varied from 1.03 to 2.57mSvyear-1 with an average value of 1.59mSvyear-1. The assessed values have been contrasted with the limit suggested by the UNSCEAR and the ICRP and were found to be within the permissible level. The normality of frequency distribution curves of 222Rn and 220Rn concentrations was assessed by the Kolmogorov-Smirnov test.

Results of Indoor Radon Measurements in Campania Schools Carried Out by Students of an Italian Outreach Project

Outreach projects are often used to a limited extent for dissemination purposes and rarely have a significant impact on the student’s teaching and technical skills. The RadioLab project requires a proactive interaction between researchers and students by experimental activities for measuring environmental radioactivity, in particular radon gas. Buildings considered to be of radiological interest, such as schools, have been selected to carry out radon gas activity concentration measurements using solid-state nuclear track passive detectors LR-115. The results of annual measurements, made over 6 years and involving a total of 952 rooms, distributed in 67 schools throughout the Campania region, were collected. These data, deemed scientifically reliable (i) can be overlapped over geological characterization data enhancing the relationship between lithology and radon, (ii) confirmed data from the radon potential map of the Campania region about the distribution of indoor radon, and finally (iii) contributed to the collection of radon indoor data of the Campania region. The results obtained highlighted the need and effectiveness of increasing the network of schools involved in the outreach activity and in the implementation of experimental activities with applicative effects in the scientific and research sectors.

TIME SERIES ANALYSIS OF RADON CONCENTRATION AT DIFFERENT DEPTHS IN AN UNDERGROUND GOLDMINE

Indoor radon concentrations were collected monthly over a period of one year in 10 different levels in an underground goldmine and the data was analysed using a four moving average time series to determine the relationship between depths of the underground mine and the indoor radon concentration. The detectors were installed in batches within four quarters. The measurements were carried out using LR115 solid state nuclear track detectors. Statistical models are applied in the prediction and analysis of the radon concentration at various depths. The time series model predicted a positive relationship between the depth of the underground mine and the indoor radon concentration. Thus, elevated radon concentrations are expected at deeper levels of the underground mine, but the relationship was insignificant at the 5% level of significance with a negative adjusted R 2 (R 2 = – 0.021) due to an appropriate engineering and adequate ventilation rate in the underground mine. Keywords : LR115, Radon Concentration, Time Series, Underground goldmine, DOI: 10.7176/APTA/87-03 Publication date: April 30 th 2023

Recoil Proton Telescopes and Parallel Plate Avalanche Counters for the 235U(n,f) cross section measurement relative to H(n,n)H between 10 and 450 MeV neutron energy

With the aim of measuring the 235U(n,f) cross section at the n_TOF facility at CERN over a wide neutron energy range, a detection system consisting of two fission detectors and three detectors for neutron flux determination was realized. The neutron flux detectors are Recoil Proton Telescopes (RPTs), based on scintillators and solid state detectors, conceived to detect recoil protons from the neutron-proton elastic scattering reaction. This system, along with a fission chamber and an array of parallel plate avalanche counters for fission event detection, was installed for the measurement at the n_TOF facility in 2018, at CERN.An overview of the performances of two RPTs — especially developed for this measurement — and of theparallel plate avalanche counters are described in this article. In particular, the characterizationin terms of detection efficiency by Monte Carlo simulations and response to neutron beam, the studyof the background, dead time correction and characterization of the samples, are reported. Theresults of the present investigation show that the performances of these detectors are suitable foraccurate measurements of fission reaction cross sections in the range from 10 to 450 MeV.

Segmented silicon-based solid-state detector with thin dead layer for superheavy element research

Silicon-based solid-state detectors (SSDs) are crucial for investigating the properties of superheavy elements (SHEs), since they measure the energy of SHEs and charged particles that are emitted as successive decay events of the SHEs. We have developed a segmented SSD for SHE studies using the new gas-filled recoil ion separators (GARIS-II and GARIS-III) at RIKEN. It is based on a back-illuminated Si PIN photodiode in which the irradiation is through the N+ layer. The detector is introduced as a side one for the GARIS focal plane detection system. To investigate the characteristics of the SSD, 241Am α particles were irradiated by automatically moving and rotating the α source for each segmented portion of the SSD. A Monte Carlo simulation was also performed to estimate the dead layer thickness of the segmented SSD.

RADON CONCENTRATION MEASUREMENT AND DOSE ESTIMATION IN NON-URANIUM MINES IN CHINA (2019-21).

The radon concentration in selected non-uranium mines from 2019 to 2021 in China are presented. By using of solid-state nuclear track detector, a total of 110 non-uranium mines in 13 provinces and autonomous regions were monitored, and the data were analyzed according to the mineral categories. The arithmetic mean of radon concentration in underground metal mines and nonmetallic mines were 1180 and 162Bq m-3, respectively, and the standard deviations were 2850 and 151Bq m-3, respectively. Correspondingly, the average annual effective dose of metal miners was 12.7mSv and that of nonmetal miners was 1.75mSv. It was noted that the radon concentration in some metal mines is not optimal in China. It is suggested that the ventilation should be strengthened in some metal mines. Besides, it is still necessary to control occupational radon exposure of non-uranium miners as low as reasonably achievable, and non-uranium mines should be managed by classification.

A Fully Integrated Solid-State Charge Detector with through Fused Silica Glass via Process

A charge detector is a vital component in neutrino and dark matter detection. The integration of a charge collector in the form of flat pads and readout modules has been proposed as an optimization method as it can reduce noise and installation complexity. As a substrate, fused silica glass has attracted considerable attention due to its low radioactive background properties. In this research, based on the application requirements of a high charge collection rate and low noise, the structure of the charge detector was designed using calculation and simulation methods. The entire manufacturing process is described. In addition, a novel through glass via (TGV) structure composed of a conformal metal layer and a photosensitive material that is easy to fabricate and has high morphological compatibility with via filling is proposed. The curing property of the new material was characterized. A fully integrated solid-state charge detector with 32 groups of TGVs was realized. Additionally, the electrical properties of key structures were tested and analyzed.