High-purity Germanium Detector Research Articles

Absolute mass calibration of fission product distributions measured with the E-[formula omitted] method

The mass calibration of fission product distributions measured with the energy–velocity (E-υ) method constitutes a technical challenge. The energy loss of the fission fragments in the various dead layers of the spectrometer and other sources of pulse-height defects of the energy detectors are a significant source of systematic uncertainty in the mass calculations used to determine the measured fission product yields. In this study, the absolute calibration of the fission mass distributions is accomplished by measuring prompt γ-rays in coincidence with the fission fragments. This allows for the direct calibration of the mass spectra and eliminates any dependence on potentially complicated energy corrections. The first test measurement was performed at the Los Alamos Neutron Science Center employing the SPectrometer for Ion DEtermination in fission Research (SPIDER). SPIDER is a 2E-2υ spectrometer designed for measuring independent fission product yields from neutron-induced fission. In this test, the single-arm SPIDER (E-υ) system and an array of 252Cf sources were used. The single-arm system consisted of two time pick-off detectors for measuring the time-of-flight of the fission fragments and a double-sided silicon strip detector (DSSD) for measuring the kinetic energy. Characteristic γ-rays from fission fragments were detected using three high-purity germanium (HPGe) detectors. For the mass calibration, γ–mass coincidence events from twelve product isotopes were used. The measured FPYs from 252Cf spontaneous fission were found to be in excellent agreement with the evaluated data after applying the absolute mass calibration. From the γ–mass coincidence events, the mass resolution of the system was also extracted. An average mass resolution of ∼1.4 AMU (FWHM) for the light fragments and ∼2.4 AMU (FWHM) for the heavy fragments were found. This was the first in-situ calibration and characterization of the SPIDER spectrometer, which paves the way for high-quality FPY measurements with this instrument.

Calculating off-axis efficiency of coaxial HPGe detectors by Monte Carlo simulation

In beam geometries where a directed γ-ray beam hits the surface of a coaxial high purity germanium detector (HPGe), the detector efficiency is sensitive to the position where γ-rays initially hit the detector surface because the structure of the detector is nonuniform. This may cause inaccuracy of the detector efficiency when measured using standard sources that are point-like sources emitting γ-rays isotropically. Obtaining a precise estimation of the full energy peak efficiency of the coaxial HPGe detector in the beam geometry for on-axis and off-axis measurements requires a Monte Carlo simulation. We performed Monte Carlo simulations that calculate the detector efficiency in the beam geometry. The effects of the off-axis distance and γ-ray beam size on the efficiency are quantitatively analyzed. We found that the intrinsic efficiency in the beam geometry is maximized when the beam hits the detector at specific off-axis distances. Our Monte Carlo calculations have been supported by nuclear resonance fluorescence experiments using laser Compton scattering γ-ray beams.

Radioactivity distribution in soil samples of the Baba Gurgur dome of Kirkuk oil field in Iraq

ABSTRACT This work presents a study of radioactivity in soil samples from oil well sites of Baba Gurgur dome of Kirkuk oil field using a high-purity germanium (HPGe) detector and spectroscopy system. The activity concentration (Bq kg−1) of 226Ra, 232Th, 40K and 137Cs varied between 26.4–98, 10.8–55.2, 239–729, and 2.40–7.20, respectively. The results have been compared with the average worldwide values. The hazard indices have also been calculated. The radium equivalent activity (Raeq) was 131.04 Bq kg−1, the absorbed gamma dose rate (D) was 62.04 nGy h−1, the annual effective dose rate (AEDE) outdoor and indoor were 0.08 mSv y−1 and 0.30 mSv y−1, respectively, the external hazard (Hex) was 0.35, the internal hazard (Hin) was 0.51, the Gamma radiation representative level Index (Iγ) was 0.96, and excess lifetime cancer risk was 0.30 × 10−3. Our results of some sites were found to be higher than the allowable worldwide values. Statistical data including: Mean, Median, Std. Deviation, kurtosis, skewness, box plot, frequency distribution, Quantile-quantile (Q-Q) plots, Pearson’s correlation coefficient analysis, principal component analysis (PCA), and cluster analysis were calculated and carried out to explain our results.

Synthesis and experimental characterization on fast neutron and gamma-ray attenuation properties of high-dense and transparent Cadmium oxide (CdO) glasses for shielding purposes

We present synthesis and thorough characterization phases of newly developed 20P2O5·30TeO2.(50-x)ZnO.xCdO (x = 0, 2, 4, 6, 8, 10 mol%) glasses. Experimental gamma-ray and neutron transmission systems are used in terms of exploring the monotonic effects of increasing CdO reinforcement on behavioural changes of synthesized glasses through well-known melt-quenching method. A conventional gamma-ray setup along with a high purity germanium detector as well as 133Ba radioisotope is used for determination of attenuation coefficients. Glass shields are irradiated with a241Am/Be neutron source using the Canberra NP-100B BF3 gas proportional detector. The addition of 10% mole CdO to the basic glass composition had a significant favorable impact on the transition resistance to gamma and neutron radiation. In comparison to all available shielding materials, (except RS-520), the C10 sample demonstrated superior gamma-ray attenuation capabilities. According to results, C glasses generally exhibit superior neutron attenuation capabilities than conventional moderators. It can be concluded that C glass family may be considered as suitable gamma-shield and neutron moderator in different types of applications from research to medical radiation fields.

Volume reduction of water samples to increase sensitivity for radioassay of lead contamination

The World Health Organisation (WHO) presents an upper limit for lead in drinking water of 10 parts per billion ppb. Typically, to reach this level of sensitivity, expensive metrology is required. To increase the sensitivity range of low-cost devices, this paper explores the prospects of using a volume reduction technique of a boiled water sample doped with Lead-210 ({}^{210} Pb), as a means to increase the solute’s concentration. {}^{210}Pb is a radioactive lead isotope and its concentration in a water sample can be measured with e.g. High Purity Germanium (HPGe) detectors at the Boulby Underground Germanium Suite. Concentrations close to the WHO limit have not been examined. This paper presents a measurement of the volume reduction technique retaining 99pm (9)% of {}^{210}Pb starting from a concentration of 1.9 times 10^{-6} ppb before reduction and resulting in 2.63 times 10^{-4} ppb after reduction. This work also applies the volume reduction technique to London tap water and reports the radioassay results from gamma counting in HPGe detectors. Among other radio-isotopes, {}^{40}K, {}^{210}Pb, {}^{131}I and {}^{177}Lu were identified at measured concentrations of 2.83 times 10^{3} ppb, 2.55 times 10^{-7} ppb, 5.06 times 10^{-10} ppb and 5.84 times 10^{-10} ppb in the London tap water sample. This technique retained {90 pm 50}{%} of {}^{40}K. Stable lead was inferred from the same water sample at a measured concentration of 0.012 ppb, prior to reduction.

P-process chaser detector in [formula omitted] - [formula omitted] coincidences

We propose two types of neutron-γ1−γ2 triple coincidence detectors (not constructed) to chase gamma transitions to produce p-nuclei following the neutron emission in the (γ,n) reaction. Neutrons are detected with 24 3He counters embedded in a polyethylene moderator in Type I detector and with 6 liquid scintillation detectors in Type II detector, respectively. γ rays are detected with two high-purity germanium detectors and four LaBr3(Ce) detectors. The detector which is referred to as p-process chaser detector is used to search for mediating states in 180Ta through which the isomeric and ground states in 180Ta are thermalized in the p-process. A search is made for both resonant states and unresolved states in high nuclear-level-density domain.

Contextual Isotope Ranking Criteria for Peak Identification in Gamma Spectroscopy Using a Large Database

Isotope identification is a recurrent problem in gamma spectroscopy with high purity germanium detectors. In this work, new strategies are introduced to facilitate this type of analysis. Five criteria are used to identify the parent isotopes making a query on a large database of gamma-lines from a multitude of isotopes producing an output list whose entries are sorted so that the gamma-lines with the highest chance of being present in a sample are placed at the top. A metric to evaluate the performance of the different criteria is introduced and used to compare them. Two of the criteria are found to be superior than the others: one based on fuzzy logic, and another that makes use of the gamma relative emission probabilities. A program called histoGe implements these criteria using a SQLite database containing the gamma-lines of isotopes which was parsed from WWW Table of Radioactive Isotopes. histoGe is Free Software and is provided along with the database so they can be used to analyze spectra obtained with generic gamma-ray detectors.

Analysis of natural and artificial radioactive emission pattern in Qarasu River catchment in Gorgan Bay, northern Iran

Knowledge of distribution and emission pattern of natural and artificial radioactive elements and their radiation level in the environment is very important to assess its effects on human health and living organisms. In this study, the specific activity of natural and artificial radioactive elements for 30 soil and sediment samples collected from upstream and the outlet of Qarasu River to Gorgan Bay as well as sediments in the eastern part of Gorgan Bay were measured using High-Purity Germanium detector and their distribution map with using SURFER and GIS software was drawn. Specific activity of 226Ra, 232Th, 40K and 137Cs was obtained from 8.80 to 31.92, from 11.16 to 43.19, from 183.77 to 562.88 and from 0.83 to 12.72 in Bq/kg respectively. Upstream of the Qarasu River, the average concentration of 226Ra, 232Th, 40K and 137Cs in the soil samples beside the Qarasu River was higher than the sediments of the river, which indicates the washing of sediments and the transport of radioactive elements by water flow and transfer of these elements to lower areas. In Qarasu estuary and Gorgan Bay, 232Th and 40K distribution patterns are almost similar and the highest concentrations of 226Ra, 232Th and 40K elements are related to Qarasu estuary sediments. The concentration of 137Cs in the mouth of Qarasu River has the lowest value and increases with its distance from the mouth to the middle parts of Gorgan Bay, which indicates a high mobility and a tendency to sediment in calmer places for 137Cs. The measured values for radiological parameters and risk indices due to nuclear radiation in this study are within the allowable range and the amount of available nuclear radiation does not threaten the health of the inhabitants of the region‎‎‎.‎

The Majorana Demonstrator readout electronics system

The Majorana Demonstrator comprises two arrays of high-purity germanium detectors constructed to search for neutrinoless double-beta decay in 76Ge and other physics beyond the Standard Model. Its readout electronics were designed to have low electronic noise, and radioactive backgrounds were minimized by using low-mass components and low-radioactivity materials near the detectors. This paper provides a description of all components of the Majorana Demonstrator readout electronics, spanning the front-end electronics and internal cabling, back-end electronics, digitizer, and power supplies, along with the grounding scheme. The spectroscopic performance achieved with these readout electronics is also demonstrated.

Determination of the Radon Concentration of Gas 222Rn Emitted From Sludge Samples Located in the Radioactive Waste Collection Warehouse in Khader Al-Maa South of Basra City – Iraq

Thirty-one samples of sludge were taken, stored at the natural radioactive waste collection site, NORM, in Khidir Al-Maa, south of Basra city, resulting from the operations of extracting and filtering crude oil in oil fields in Basra Oil Company, to determine gas concentrations Radon 222Rn and other radioisotopes in Sludge models. The rapid electronic technology was adopted through the RAD7 device, the active method, and the gamma analysis technique using HPGe High Purity Germanium Detectors to determine the specific activity of radioactive elements. The measurements for this study showed 98463±7031 Bq.m-3 in sample no. S10 a barrel of sludge was brought from the third Degassing Station plant in the northern Rumaila oil field and least concentrated is 8317±594 Bq.m-3 in sample no. S14 sludge belonging to the sixth Degassing Station / West Qurna-1, the study also revealed the presence of high concentrations of the specific effectiveness of radioactive isotopes (214Pb, 212Bi, 226Ra) and (212Pb, 212Bi, 228Ac) of the uranium-238 series and Thorium-232 series in a sludge form selected from a barrel returning to the third gas isolation plant - North Rumaila Oilfield and stockpile at the collection site, where the specific activity value of radium was 226 Ra 133851 Bq.k-1 of the uranium-238 series and for lead 212Pb 56432 Bq.k-1 of For uranium-238 series compared to their concentrations, 32 Bq.k-1 45 Bq.k-1 in a natural soil model. The effective dose to which on-site workers would be exposed in contact was calculated and found to be 196.92 Svh-1, a dose that exceeded the proposed 50 Sv. h-1 dose limits by the US EPA. The probability of developing cancer due to exposure to radon per million people was found and it was found to be a high value compared to the suggested value (170-230) per million people previously by ICRP.

Koncentracija aktivnosti prirodnih radionuklida u hrani za piliće u Republici Sjevernoj Makedoniji

The care of radioactivity level in animal feed is very important, as ingestion is one of the most common ways radionuclides enter living organisms. Thus, since humans consume products of animal origin (eggs and poultry, milk and beef), it is important to monitor radiation levels in animal feed, as part of the radioactivity that these animals are exposed to, could be transmitted to humans. Natural radionuclides such as 40K, 232Th and 226Ra find their way into the food chain from soil and air to plants and from plants to animals and humans as well. The goal of this study was to determine the activity concentrations of natural radionuclides in three commercial chicken feeds – starter, grower and finisher. The analyzes were performed by means of HPGe gamma spectrometry - gamma spectrometer (Canberra Packard) with a high-purity germanium detector. The obtained spectra from the measurement were analyzed by using the program GENIE 2000. Based on the performed tests, the mean values for the activity concentrations in the samples were the following 26.03±4.1 Bq kg-1 for 226Ra, 37.9±4.8 Bq kg-1 for 232Th, and 64.40±6.5 Bq kg-1 for 40K. The results obtained from the analyses of chicken feeds were compared to studies in other countries and it was found that 40K was present in the highest amount in all types of samples while the vales for the other natural radionuclides were within the nominal concentrations. Higher concentration of 40K can be associated with plants used in the production of animal feed, which were contaminated with fertilizer during their cultivation. The range of radionuclide concentrations in the samples was within the recommended values UNSCEAR.

Evaluation of environmental radioactivity in soils around a coal burning power plant and a coal mining area in Barapukuria, Bangladesh: Radiological risks assessment

To study the distributions and potential dispersions of naturally occurring radioactive materials (NORMs: 226Ra, 232Th, and 40K) from coal-based activities (Barapukuria, Bangladesh), we studied a suite of systematically collected surface and sub-surface soil samples by X-ray fluorescence and high purity germanium detector based γ-spectroscopy. The average (range) radioactivities of 226Ra, 232Th, and 40K in the studied soil samples were 80.6 (33.0–118.0), 104.4 (43.0–182.0), and 508.1 (318.3–743.4) Bq.kg−1, respectively, which are significantly higher than the corresponding world average value. No significant fractionations of NORMs were observed between the surface and sub-surface soils, except for 232Th. Along with the anthropogenic origin, several geochemical processes (e.g., weathering, mineralogical dissolution/precipitation, alteration, leaching, differential solubility mediated geochemical mobility etc.) play significant role in NORM distributions. Major-oxide abundances, indices-based calculations, and correlation studies on the measured parameters revealed the natural processes (e.g., geochemical mobility, mineralogical distributions, water logging based differential solubility) responsible for NORM distributions. In terms of mean radium equivalent activity, internal hazard index, and total annual effective dose values, the studied area possesses trivial radiological risks, whereas the values of internal absorbed gamma dose and excess lifetime cancer risk demonstrate significant health hazards. Considering the adverse radiological risks originating from coal-based industrial activities and the long half-lives of NORMs, the present scenario will potentially be deteriorated.

Achieving sub-pixel position resolution and sub-millimeter depth resolution using a pixelated CdZnTe detector

The CdZnTe detector, a room-temperature semiconductor detector, has many applications for nuclear safety and nuclear medicine because of its high energy resolution and small size when compared with scintillator detector and high purity Germanium detector respectively. Radionuclide imaging is one of the most important applications that requires adequate three-dimensional position resolution. In this work, we used a CdZnTe crystal from eV Products with a pixelated anode to achieve approximately 1.0 mm position resolution on an electrode plane and 0.9 mm position resolution in depth when the CdZnTe detector’s pixel pitch is 2 mm and thickness is 5 mm. We also improved the energy resolution of a 662 keV full-energy peak in a 137Cs energy spectrum to 1.27% after running a selection of full-energy deposited events based on depth, compared with 4.06% without this operation.

The DESPEC setup for GSI and FAIR

The DEcay SPECtroscopy (DESPEC) setup for nuclear structure investigations was developed and commissioned at GSI, Germany in preparation for a full campaign of experiments at the FRS and Super-FRS. In this paper, we report on the first employment of the setup in the hybrid configuration with the AIDA implanter coupled to the FATIMA LaBr3(Ce) fast-timing array, and high-purity germanium detectors. Initial results are shown from the first experiments carried out with the setup. An overview of the setup and function is discussed, including technical advancements along the path.

Simulation and validation of a planar HPGe detector signal database for use in pulse shape analysis

Due to their excellent spectroscopic capabilities and sensitivity to the position of γ-ray interactions, segmented High-Purity Germanium (HPGe) detectors are frequently used in γ-ray imaging applications. The quality of produced images is heavily dependent on the precision of the identification of interaction position within the detector that can be achieved through segmentation and the application of pulse shape analysis (PSA) techniques. In this work, a simulated database of signals was produced for a HPGe planar detector used in a multi-tiered Compton camera system. The impurity concentration and temperature-dependent mobility parameters of the simulation were optimised and validated by evaluating the pulse-shape response at select positions using experimentally-measured collimated γ-beam data. A grid-search algorithm was developed for analysis of single and double-site γ-ray interactions using signal comparison PSA and is shown to improve the position resolution within the detector.

Assessment of the associated particle technique with high-resolution gamma-ray spectroscopy for in-field identification of chemical warfare agents and explosives

High-resolution prompt γ-ray neutron activation analysis (PGNAA) is performed using the associated particle (AP) technique with a deuterium–tritium neutron generator and high-purity germanium detector. Although the time resolution is inferior compared to similar systems employing fast scintillation γ-ray detectors, the strong background suppression combined with the high γ-ray energy resolution provides an important boost in sensitivity to certain key elements, especially relevant to field measurements of complex chemicals encased within thick layers of metal, such as in recovered chemical warfare (CW) munitions. Results for various CW and explosive simulants contained within mock munitions are presented and compared with results obtained from traditional PGNAA measurements without the aid of the AP technique. Significant improvements in identification and discrimination between certain chemicals are achieved with the high energy resolution AP technique.

Investigation and mapping of natural and artificial radioactivity in sediment samples from Borçka Black Lake, Artvin-Turkey

ABSTRACT All living creatures in nature are constantly exposed to ionising radiation, which is emitted from natural and artificial radiation sources. For this reason, it is important to monitor the levels of radioactivity in living spaces and visited areas. In this study, natural (238U, 232Th, 40K) and artificial (137Cs) radioactivity concentrations in sediment samples taken from Borçka Black Lake located on the Nature Park in Artvin province were determined using a high purity germanium detector (HPGe). It was determined that 238U, 232Th, 40K and 137Cs radioisotope concentrations in the sediment samples varied between 8.73 and 26.45, 7.01 and 22.98, 289.92 and 578.98, and 6.26 and 70.96 Bq kg−1, respectively. Mean radioactivity concentrations were found to be 14.99 ± 0.89 Bq kg−1 for 238U, 13.85 ± 1.10 Bq kg−1 for 232Th, 473.67 ± 14.21 Bq kg−1 for 40K and 35.06 ± 0.96 Bq kg−1 for 137Cs. In order to evaluate the radiological hazards, radium equivalent activity, external hazard index, absorbed dose rate in the air, the annual effective dose rate and excess life time cancer risk were calculated and compared with the values recommended by international organisations. As a result, it has been shown with this study that the radioactivity caused by the examined radioisotopes will not pose any health risk for the visitors of Borçka Black Lake.

Calculation of Spatial Response of a Collimated Segmented HPGe Detector for Gamma Emission Tomography by MCNP Simulations

We have proposed a planar electronically segmented high-purity germanium (HPGe) detector concept in combination with a multislit collimator for gamma emission tomography. In this work, the spatial resolution achievable using the collimated segmented HPGe detector was evaluated, prior to the manufacture and operation of the detector. The spatial response of a collimated segmented HPGe detector concept was evaluated using simulations performed with Monte Carlo N-Particle (MCNP) transport code MCNP6. The full detector and multislit collimator system were modeled, and for the quantification of the spatial response, the modulation transfer function (MTF) was chosen as a performance metric. The MTF curve was obtained through the calculation of the line spread function (LSF) by analyzing the simulated projection data. In addition, tomographic reconstructions of the simulated simplified test objects were made to demonstrate the performance of the segmented HPGe detector in planned application. For 662-keV photons, the spatial resolution obtained was approximately the same as the collimator slit width for both the 100- and 150-mm-long collimators. The corresponding spatial resolution at 1596-keV photon energy was almost twice the slit width for the 100-mm collimator, due to the partial penetration of the high-energy gamma rays through the collimator bulk. For a 150-mm-long collimator, an improved resolution was obtained.

Pulse shape analysis in Gerda Phase II

The GERmanium Detector Array (Gerda) collaboration searched for neutrinoless double-beta decay in ^{76}Ge using isotopically enriched high purity germanium detectors at the Laboratori Nazionali del Gran Sasso of INFN. After Phase I (2011–2013), the experiment benefited from several upgrades, including an additional active veto based on LAr instrumentation and a significant increase of mass by point-contact germanium detectors that improved the half-life sensitivity of Phase II (2015–2019) by an order of magnitude. At the core of the background mitigation strategy, the analysis of the time profile of individual pulses provides a powerful topological discrimination of signal-like and background-like events. Data from regular ^{228}Th calibrations and physics data were both considered in the evaluation of the pulse shape discrimination performance. In this work, we describe the various methods applied to the data collected in Gerda Phase II corresponding to an exposure of 103.7 kg year. These methods suppress the background by a factor of about 5 in the region of interest around Q_{beta beta }= 2039 keV, while preserving (81pm 3)% of the signal. In addition, an exhaustive list of parameters is provided which were used in the final data analysis.

Study of Naturally Occurring Radioactive Material Present in Deep Soil of the Malwa Region of Punjab State of India Using Low Level Background Gamma-Ray Spectrometry

Background: Epidemiological observations such as mental retardation, physical deformities, etc., in children besides different types of cancer in the adult population of the Malwa region have been reported. The present study is designed to get insight into the role of naturally occurring radioactive material (NORM) in causing detrimental health effects observed in the general population of this region.Materials and Methods: Deep soil samples were collected from different locations in the Malwa region. Their activity concentrations were determined using low-level background gammaray spectrometry. High efficiency and high purity germanium detector capped in a lead-shielded chamber having a resolution of 1.8 keV at 1,173 keV and 2.0 keV at the 1,332 keV line of 60Co was used in the present work. Data were evaluated with Genie-2000 software.Results and Discussion: Mean activity concentrations of 238U, 232Th, and 40K in deep soil were found to be 101.3 Bq/kg, 65.8 Bq/kg, and 688.6 Bq/kg, respectively. The mean activity concentration of 238U was found to be three and half times higher than the global average prescribed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). It was further observed that the activity concentration of 232Th and 40K has a magnitude that is nearly one and half times higher than the global average prescribed by UNSCEAR. In addition, the radioisotope 137Cs which is likely to have its origin in radiation fallout was also observed. It is postulated that the NORM present in high quantity in deep soil somehow get mobilized into the water aquifers used by the general population and thereby causing harmful health problems.Conclusion: It can be stated that the present work has been able to demonstrate the use of low background gamma-ray spectrometry to understand the role of NORM in causing health-related effects in a general population of the Malwa region of Punjab, India.