High-purity Germanium Detector Research Articles

Development of a low-background HPGe detector at Kamioka Observatory

Abstract A new ultra-low background high-purity germanium (HPGe) detector has been installed at the Kamioka underground experimental site. The background count rate in the energy range from 40 keV to 2700 keV is about 25% lower than that of the first HPGe detector installed in 2016, which has the same detector specification and similar shielding geometry. This paper describes the shielding configuration, including the cleaning of the material surface, the comparison of calibration data and simulation, the time variation of the background spectra, the sample measurement procedure, and some results of the radioactivity in the selected samples.

Contributions of 238U, 232Th, and 40K to the radiogenic heat production in selected river sediment samples of South Africa

In this study, 16 sediment samples were collected from Bree, Klein-Brak, Bakens and uMngeni rivers of South Africa and were prepared, analysed and evaluated for the activity concentration of 238U, 232Th and 40K concerning its radiogenic heat production using a high-purity germanium detector. The results show that 238U is the prevalent radionuclide in radiogenic heat production, with 232Th and 40K emerging as trace elements. The mean activity concentrations are 28.97%, 63.69% and 7.34% for uranium, thorium and potassium, respectively, from all sampling locations. This shows that a high radioactive concentration of a specific radionuclide does not necessarily imply its increased contribution to radiogenic heat production. The radionuclide contributions to radiogenic heat production at all sampled locations are 59.39%, 35.11% and 5.50% for uranium, thorium and potassium, respectively. The mean radiogenic heat production rate in the study area ranged from 0.0180 μW m − 3 in sediment samples from the Bree River in Western Cape to 0.0072 μW m − 3 in sediment samples of uMgeni River in KwaZulu-Natal. All values obtained for this study are five times lower than the average continental radiogenic heat production of 1 μW m − 3 . This study provides insight into the radiogenic heat production rate due to the presence of radionuclides in all river samples.

Electrical Characteristics of 3D Trench Electrode Germanium Detector with Nested Complementary Cathodes.

High-purity germanium detectors, widely employed in fields such as aerospace applications based on radiation detection principles, have garnered attention due to their broad detection range and fast response time. However, these detectors often require larger sensitive area volumes to achieve larger signals and higher detection efficiency. Additionally, the large distance between the electrodes contributes to an issue of incomplete charge collection, which significantly restricts their application in space applications. To enhance the electrical performance of high-purity germanium detectors, this study introduces a strategy: designing the detector's cathode electrode into a 3D trench shape with nested complementary cathodes. This design greatly reduces the electrode spacing, endowing the detector with superior electrical characteristics, such as a smaller dead zone and improved charge collection efficiency. Performance simulations of the novel detector structure were conducted using the semiconductor device simulation software Sentaurus TCAD (2019.03). The simulation results confirmed that the nested complementary 3D trench electrode high-purity germanium detector exhibits excellent electrical features, including a larger sensitive area volume, rapid charge collection, and good cell isolations. This approach has the potential to effectively expand the application scenarios of high-purity germanium detectors. Depending on different operational environments and requirements, nested complementary 3D trench electrode high-purity germanium detectors of appropriate structural dimensions can be chosen. The experimental findings of this study hold a significant reference value for enhancing the overall structure of high purity germanium detectors and facilitating their practical application in the future.

Natural radioactivity concentration measurements in shrimp and sea bass samples from the Mexican Pacific Ocean and the Gulf of Mexico

The radioactivity concentration for shrimp and sea bass retrieved from the Mexican Pacific Ocean and the Gulf of Mexico is reported in this work. The activity of 40K and 208Tl was determined with gamma spectroscopy using a High Purity Germanium detector. Overall, the radioactivity concentration of samples from the Mexican Pacific Ocean is higher than from the Gulf of Mexico. The 40K concentration measured for shrimp is 575 ± 14 Bq/kg (Pacific) and 443 ± 10 Bq/kg (Gulf), while the activity for sea bass is 753 ± 18 Bq/kg (Pacific) and 502 ± 14 Bq/kg (Gulf). Similarly, the measured concentration of 208Tl for shrimp and sea bass is 0.75 ± 0.03 and 1.09 ± 0.05 Bq/kg (Pacific), respectively, and 0.51 ± 0.02 and 0.85 ± 0.04 Bq/kg (Gulf), respectively. No other natural radionuclides or radiation contaminants were observed with significant activity. This is the first comparison of radioactivity concentration in fish and shellfish between the two main Mexican marine ecosystems.

A new fast screening method for estimating building materials hazard indices with correlated inputs

In this work we investigate a new fast screening method for estimation of chosen hazard indices (HI) using correlated inputs dedicated for small 3.00 g samples using a novel μDOSE. The system detects α and β particles separately, along with 220Rn/216Po, 219Rn/215Po, 212Bi/212Po and 214Bi/214Po decay pairs. Four separate decay pairs along with α and β particle count rates are used to quantify decay chains. The excess β count rates is used to quantify the 40K radioactivity. This provides radionuclide estimates that are correlated—and this correlation is taken into account in calculating hazard indices with their corresponding uncertainties. Calculated hazard indices are verified against state-of-the-art High Resolution Gamma Spectrometry (HRGS) equipped with a High Purity Germanium (HPGe) detector manufactured by Canberra. This research shows that results obtained with the μDOSE system correspond to the results obtained with HRGS and when the activity correlation is taken into account the HI uncertainties are similar in value for both methods.

Assessment of natural and anthropogenic radioactivity levels and their radiological hazards in surface soil samples around oil refinery, Little Aden City, Yemen

The activity concentration of global fallout of 137Cs and naturally- occurring radioactive materials (NORM), which primarily due to the geological and geographical condition of soil. and maybe occur from oil and gas burring processes and consequently accumulate on surface soil around the oil refinery in Aden Assoghra city, Yemen were studied by use the gamma-ray spectrometer equipped with a high purity germanium (HPGe) detector and specially designed shield. The average concentrations of 226Ra, 232Th, and 40K expressed in (Bq kg−1) of the studied samples were (13 ± 0.44) Bq kg−1, (22.1 ± 0.64) Bq kg−1 and (509 ± 9) Bq kg−1, respectively. Low concentrations of 137Cs were noted from some sample in the study area, where ranged from (0.3 ± 0.2) to (1.7 ± 0.2) Bq kg-1. The average values of calculated radiological hazard indices were 40.6 nGy h−1 (absorbed dose rate outdoors), 0.05 mSv y−1 (annual effective dose outdoors), 0.279 mSv y−1 (annual effective dose indoors), 83.7 Bq kg−1 (radium equivalent), 0.23 (external hazard index), 0.26 (internal hazard index), 0.65 (representative level index), 0.174×10-3 (the excess lifetime cancer risk ELCR) and 0.292mSv y−1 (annual gonadal equivalent dose, AGED).

Characterization and experimental investigation for gamma–ray shielding competence of basalt-doped polyethylene nanocomposites

Experimental investigations on gamma - rays attenuation parameters and dielectric spectroscopic properties were done on a polymeric mixture with chemical composition (100-x) polyethylene + x basalt, where x = 0, 1, 3, 5, 10, and 20 wt%. Using the melting blending technique,six nanocomposite polymeric samples were prepared. The linear attenuation coefficient μ of each prepared set of samples was measured using a gamma-ray spectrometer including High Purity Germanium detector (HPGe) at energies 662.5, 1173.24, and 1332.51 keV. Based on the measured values of (μ) and sample density, the other effective shielding parameters were calculated. the values of μ showed an increase with increasing the dopant ratios from 0.0 up to 20.0 wt%. In addition, the μ values decreased with the photon's energy. The μ values were found 0.0847 up to 0.1175 cm−1, 0.0571 up to 0.0855 cm−1, and 0.0543 up to 0.075 cm−1 at 662.5, 1173.24, and 1332.51 keV. for B0 up to B20, respectively. The ATR spectroscopy was done on the prepared samples, and a good evidence of adding the filler to the pure polyethylene (HDPE) was obtained. Besides, an enhancement in dielectric constant by insertion of basalt NPs also recorded and can be attributed to the large dielectric constant of basalt compared to pure HDPE.

Natural Radioactivity of Granitic Rocks and Their Health Risk around Ingesana Mountains, Sudan.

This work was carried out mainly to analyze radioactive elements 40 K, 232 Th, and 226 Ra and non-radioactive elements in some granitic rocks and study their health risk for humans and non-humans. Radioisotope activity was evaluated using a high-purity germanium (HPGe) detector, and various radiological hazard indices were calculated. We also measured some non-radioactive elements using x-ray fluorescence analysis and performed Pearson correlation analysis to examine the relationships between the radionuclides and the non-radioactive elements. Furthermore, we used the ERICA software to estimate the total dose rate per organism for some non-human biota. The means of 226 Ra, 232 Th, and 40 K are 25.13 ± 5.22 Bq kg -1 , 29.01 ± 6.95 Bq kg -1 , and 323.07 ± 97.83 Bq kg -1 , respectively. Hence, 226 Ra, 232 Th, and 40 K radioactivities were lower than the worldwide average limits. The 226 Ra, 232 Th, and 40 K levels were under the global average values. The hazardous radiometric variables were computed, and the findings observed that the mean absorbed dosage was 23.48 ± 7.36 nGy h -1 , the yearly effective dose rate was 29.82 ± 10.46 μSv y -1 , and the radium equivalent activity was 88.88 ± 18.64 Bq kg -1 . The average dose and yearly effective dose rates were lower than the global average absorbed dose rate of 60 nGy h -1 and the ICRP standard of 1.0 mSv y -1 . The results of Ra-equivalent activity were lower than the recommended maximum criterion for building materials limit of Ra-equivalent activity (370 Bq kg -1 ) proposed by UNSCEAR. Tests of Pearson correlation coefficients indicate a substantial positive relationship between 226 Ra and 232 Th and a modest correlation between 226 Ra and 40 K. Meanwhile, no association between 226 Ra and 40 K and non-radioactive components has been identified. Thorium-232 exhibits a moderately favorable connection with Ti, Fe, and Ni. The estimated total dose rate per organism for the studied non-human is less than the ambient dose rate. However, the total dose rate for small burrowing mammals and reptiles exceeds the background exposure rate. In accordance with the findings, granite rocks may be safe to use as construction materials and pose no threat to human health.

Assessing radioactivity and hazards: analysis of soil, water, and coal samples near a coal-fired thermal power plant and their implications for human health and the environment

ABSTRACT The combustion of coal poses significant risks, increasing the radioactive burden on the atmosphere and affecting the health of individuals near coal mines and coal-fired thermal power plants (CFTPPs). A detailed study was conducted within a 3 km radius surrounding the site of Barapukuria Coal Mine Company Limited (BCMCL), Bangladesh’s premier operational coal-fired thermal power plant, during which 50 soil samples, 50 water samples, and 21 coal samples were collected from a variety of locations inside and beyond the BCMCL boundaries, and these samples were then analysed for radioactivity using a high-purity germanium detector. The range of activity concentrations of 226Ra, 232Th, and 40K in the studied soil, water and coal samples were 24–47, 30–76, and 340–570 Bqkg−1; 1.6–2.9, 1.1–3.8, and 53–92 Bqkg−1; 19–57, 20–97, and 78–170 Bqkg−1 respectively. The majority of hazard indices, including absorbed dose rate, gamma index, effective dose, and excess lifetime cancer risk, associated with soil samples were higher than the world average. This indicates that long-term exposure to terrestrial ionising radiation is unsafe for coal miners and the local community. The quantitative measurements of this study have important implications for planning larger and more modern coal-fired power plants. Additionally, the study’s results underscore the need for municipal officials to impose restrictions and closely monitor the release of fly ash in the vicinity of coal-fired power plants. Furthermore, there is a crucial need to monitor the health of workers and locals living near the power plant to safeguard against potential health risks.

A gamma spectroscopy-based non-destructive approach for pebble bed reactor safeguards

A gamma radiation spectroscopy study was carried out for the nuclear safeguards monitoring of fuel burnup and special nuclear material (SNM) mass in the irradiated fuel of a pebble bed reactor (PBR). The concentration of radioactive materials in irradiated PBR fuel pebbles was estimated as a function of fuel burnup for varying 235U enrichments using the Monte Carlo N-Particle (MCNP) neutronics simulation code. Gamma radiation spectra corresponding to various pebble fuel burnups were then created using MCNP modeling and simulations of a high-purity germanium (HPGe) detector. Analysis of the simulation results showed that the correlations such as (a) fuel burnup versus leftover 235U content, total Pu content, 137Cs content, 134Cs/137Cs ratio, and 154Eu/137Cs ratio; (b) 137Cs mass versus leftover 235U content, total Pu content, and fissile Pu content, and (c) 134Cs/137Cs or 154Eu/137Cs ratio versus total Pu content are sufficient to estimate pebble fuel burnup and the SNM mass.

Experimental 7Be production cross section from the [formula omitted] reaction at Ep = 3.5 − 13 MeV

The Li7(p,n)7Be reaction is widely used as neutron source for neutron induced reaction cross section measurements, and for 7Be radioactive source production. There are two prominent structures in the excitation function, a narrow resonance between Ep=2.2−2.3 MeV, and a broad peak, around Ep=5 MeV. There are tension between the experimental data sets both in the position and the width of this latter structure, as well as in the absolute scale of the data. In the present work the Li7(p,n)7Be reaction is investigated using the activation technique, with the aim of providing comprehensive cross section data covering the second structure and connecting prior literature data sets. The irradiations were performed with the Atomki cyclotron accelerator with pairs of thin foil targets, thus with precisely controlled reaction energy in the range of Ep=3.5−13 MeV. After the irradiations the activity of the samples was measured using a high-purity germanium detector. The energy uncertainty of the new data points is much smaller than in any of the previous works, while the cross section uncertainty is comparable with the most precise literature data. A consistent data set was obtained connecting the most recent and most precise literature data sets. With the new data the absolute magnitude of the Li7(p,n)7Be reaction cross section is constrained and became more precise.

Development of a new integrated IN-VIVO counting system at the QST.

A new in-vivo counting system that functions as both a whole-body counter (WBC) and a lung counter (LC) was developed at the QST to enhance its dose assessment capability. This paper presents an overview of this system and the results of its performance tests. For use of the system as a WBC, three high purity germanium (HPGe) detectors installed in a 20-cm-thick iron shielding chamber are linearly arrayed over a subject lying on the bed, whereas two of the three HPGe detectors are placed over the subject's chest from side to side when using the system as an LC. The new in-vivo system was calibrated using three de-facto phantoms owned by the QST: an adult-male BOttle Manikin ABsorption (BOMAB) phantom, a Lawrence Livermore National Laboratory (LLNL) phantom and a Japan Atomic Energy Research Institute (JAERI) phantom. Monte Carlo simulations were also performed to determine an optimum location for the three detector array in the WBC mode and revealed that the peak efficiency for the BOMAB phantom (662keV) was little varied as long as the middle detector was placed above the thorax and abdomen parts of the phantom. The calculated peak efficiencies agreed well with the observed peak efficiencies for photons with energies over 100keV. For lung counting, a tentative Minimum Detectable Activity of 241Am was evaluated as 9.5Bq for a counting time of 30minutes, and a Japanese male subject with an average chest wall thinness (2.27cm). The developed system is now ready for use.

Photon spectra in NPL standard monoenergetic neutron fields.

A High Purity Germanium (HPGe) detector has been used to measure the photon spectra in the majority of monoenergetic neutron fields produced at NPL (0.144, 0.250, 0.565, 2.0, 5.0 and 16.5MeV). The HPGe was characterised and then modelled to produce a response matrix. The measured pulse height spectra were then unfolded to produce photon fluence spectra. The new spectra were used to improve the photon to neutron dose equivalent ratios from some earlier work at NPL with Geiger-Muller tubes and electronic personal dosemeters.

Constraints on the Decay of ^{180m}Ta.

^{180m}Ta is a rare nuclear isomer whose decay has never been observed. Its remarkably long lifetime surpasses the half-lives of all other known β and electron capture decays due to the large K-spin differences and small energy differences between the isomeric and lower-energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter, and K-spin violation. For this study, we repurposed the Majorana Demonstrator, an experimental search for the neutrinoless double-beta decay of ^{76}Ge using an array of high-purity germanium detectors, to search for the decay of ^{180m}Ta. More than 17kg, the largest amount of tantalum metal ever used for such a search, was installed within the ultralow-background detector array. In this Letter, we present results from the first year of Ta data taking and provide an updated limit for the ^{180m}Ta half-life on the different decay channels. With new limits up to 1.5×10^{19} yr, we improved existing limits by 1-2 orders of magnitude which are the most sensitive searches for a single β and electron capture decay ever achieved. Over all channels, the decay can be excluded for T_{1/2}<0.29×10^{18} yr.

Estimation of photopeak efficiency for IAEA gamma standards of different geometries using HPGe and 3″x3″ NaI(Tl) gamma spectrometry systems

The IAEA certified reference gamma standards of primordial radionuclides, such as K-40, U-238, and Th-232, are analysed using gamma spectrometry systems, namely High Purity Germanium (HPGe) and 3″x3″ NaI(Tl) scintillation detectors. The analysis aims to estimate and compare the Full Energy Photopeak Efficiencies (FEPE) of these detectors for the respective gamma emission energies. Additionally, to assess the impact of sample geometry and volume on the FEPEs of the detectors, the study is extended to gamma counting of the aforementioned IAEA standards using two commonly employed sample geometries: flat-cylindrical (∼ 150 ml) and elongated-cylindrical (∼ 250 ml), usually chosen based on the sample quantity. Furthermore, the study calculates and compares the Minimum Detectable Activities (MDA) of the two detectors for the primordial radionuclides in these sample geometries. The study reveals that for both detectors, the calculated efficiency values are higher for the flat-cylindrical geometry compared to the elongated-cylindrical geometry. In contrast to FEPE, the MDA values are observed to be higher for the elongated-cylindrical geometry. The results also indicate that the values of FEPE and MDA for the 3″x3″ NaI(Tl) scintillation detector are higher than those of the HPGe detector for both geometries, in line with the expectations. This study on FEPEs and MDA of gamma detectors are crucial because precise measurements using efficient detectors with low MDAs are vital for obtaining accurate data and drawing valid conclusions.

The effect of two-part dead layer thickness on the efficiency curve of a P-TYPE HPGe detector calculated using the Monte Carlo method

The full energy peak efficiency (FEPE) of a gamma ray obtained from experimental studies using a high purity germanium detector (HPGe) can be easily reproduced by simulating the experiment in any desired geometry and energy range with Monte Carlo (MC) simulation methods. However, the dead layer (DL) thickness, which is one of the geometric information provided by the manufacturer, changes over time and affects the efficiency calculation, so it must be determined and compared with the initial value for the increases during the life-time of the detector. In this study, the general-purpose MC code PHITS and the special-purpose MC code GESPECOR were used to simulate a p-type HPGe detector and to determine the thickness of the frontal and lateral dead layer. As a result, it was observed that the frontal dead layer thickness increased from 0.7 mm to 1.075 mm, and the lateral dead layer thickness increased from 0.7 mm to 1.7 mm after 7 years of operation of the detector. This increase in dead layer thickness causes both a decrease in the detector's active volume and a decrease in efficiency in the problematic low-energy region.

Laboratory Working Out of a Space Experiment on Gamma Spectrometry of Planetary Matter with a High-Purity Germanium Detector Using the Method of Tagged Charged Particles

Laboratory Working Out of a Space Experiment on Gamma Spectrometry of Planetary Matter with a High-Purity Germanium Detector Using the Method of Tagged Charged Particles

Determination of natural radioactivity concentrations in rolled oat brands available in the Iraqi market

Abstract Oat is a nutritious healthy type of food that is widely consumed by various athletes and diet food in Iraq. This study aims to measure the natural radioactivity of potassium-40, Radium-226, and Radium-228 in rolled oat brands that are widely consumed in Iraq. Five types of oat brands retailed in Baghdad markets were collected and analyzed. A high-purity germanium detector was used for the gamma spectroscopy analysis. The mean activity concentration values of 226Ra, 228Ra, and 40K ranged from 6.9–10.6, 3.9–6.7, to 210–484 Bq/kg, respectively. The annual effective dose was the highest for a Ukrainian brand with 36.02 μSv/year, while the radium equivalent activity values range from 31.43 to 56.1 Bq/kg. The results of the study have been compared to a number of studies and showed good agreement. The findings of the paper show that regular consumption of these kinds of oats is radiologically safe for human health.

Natural radioactivity assessment of coal combustion residues produced in Indian thermal power plants using high-purity germanium detector

Abstract Huge amount of coal combustion residue (CCR) is being generated in India every year. Since coal contains some natural radionuclides, the CCR may contribute to the enhanced natural radiation background. Hence, it is important to monitor the natural radioactivity levels in Indian CCR samples. The present study aims to estimate the natural radioactivity levels in CCRs produced in Indian thermal power plants. Accordingly, six CCR samples from different thermal power plants were collected and packed to achieve secular equilibrium among daughter products of 226Ra. The samples were counted for activity of gamma radionuclides using high purity germanium detector based high resolution gamma spectrometer. Results show that 40K is the most abundant among analyzed radionuclides, and the lowest was observed for 226Ra. Secular equilibrium was observed between 228Ra and 228Th, whereas no equilibrium was observed between 226Ra and 238U. The activity concentration for 226Ra and its daughter products (214Pb and 214Bi) was found to be similar in CCR sample before and after equilibrium, indicating that progenies are in secular equilibrium in CCR. The X ray diffraction analysis of CCR indicates the presence of aluminosilicate as major fraction, which has potential of trapping of 226Ra and daughter products. The values observed are very low and similar to those observed in naturally occurring radioactive materials such as coal, soil, and sediment, hence are not of radiological concern with respect to human/environment.

Measurement of flux distribution of an AmBe neutron source and estimation of two group integral capture cross-sections

Neutron capture cross sections of elements are of utmost importance in reactor physics, dosimetry applications and stellar nucleosynthesis studies. Manipal Centre for Natural Sciences (MCNS) possesses a 16Ci AmBe neutron source, which is housed inside a concrete structure. The neutrons undergo multiple scattering events in the concrete structure and surrounding materials; therefore, the neutron flux profile is unique to this source and structural material, which differs from the standard ISO spectrum. Using this AmBe source, experiments are being conducted to understand the neutron energy distribution in two groups to measure capture cross sections of various isotopes. In the present work, gold has been used as a flux monitor, and the indium cross-section has been measured in two groups. These foils (Gold and Indium) are irradiated with and without cadmium cover to understand the neutron spectra in two spectral regions as cadmium cutoffs neutrons of energy below 0.5 eV. Irradiated samples were counted in High-Pure Germanium (HPGe) detector, and the γ-spectra obtained were used to get the epi‑cadmium (0.5 eV and above) to total ratio of ⟨σ(E)ϕ(E)⟩. The neutron flux is estimated in two groups corresponding to thermal (thermal energy neutron extended up to 0.5 eV) and epi‑cadmium regions, and also the flux-weighted capture cross sections of 115In are determined.