High-purity Germanium Detector Research Articles

Measured low-energy x-ray spectra of interest in diagnostic radiology and mammography

Objective. In cities situated at high-altitude, the measured x-ray spectra are required to calculate the absorbed dose to water in radiobiology and medical dosimetry because of the air-density effect. This work aims to measure, in a high-altitude city, a set of x-ray spectra from an x-ray tube with tungsten anode generated at potentials of the M-series x-ray beams from NIST in the range of 20 and 150 kV as well as other beam qualities that have been characterized and used for dosimetry study in our group called W-series. To also measure some spectra of mammography interest in the energy range of 25 and 35 kV using additional filtration of rhodium (Rh), molybdenum (Mo) and silver (Ag). Approach. A tungsten anode x-ray tube with potential between 10 to and 160 kV was used. A high-purity germanium (HPGe) detector associated with a DSPEC Jr 2.0TM digital signal processing module has been used for the spectra measurements. Prior the spectra measurements, the HPGe detector has been characterized and calibrated using several radioactive sources. Main results. The M80 spectrum was compared to a mathematically filtered beam from Physicalisch Technische Bundesanstalt corresponding to the same potential finding a difference of 0.7% in the average energy. So, the mathematically filtered beam from PTB matches very well our M80 beam. The beams M80, M100 and M120 were also compared with calculations for the corresponding kilovoltage from an executable that calculates x-ray spectra from tungsten anode x-ray tubes in the energy range between 40 to 300 kV called SpekCalc. The SpekCalc reproduces qualitatively the experimental spectra, but not quantitatively, mainly for M100 and M120 beams. Significance. These spectra can be used to simulate the patient dose as well as image quality using Monte Carlo (MC) codes or to evaluate the absorbed dose in dosimetry studies

Determination of the Potassium Content in Fruit Samples by Gamma Spectrometry to Emphasize its Health Implications

In this study, the activity concentration of 40K and its’ concentrations in 24 different types of fruits were determined using high purity germanium (HPGe) and sodium iodide scintillation (NaI) detectors. The results of the two measurements are consistent. The Maximum and minimum activities of 40K in dry samples were 750.61 ± 11.88 and 15.64 ± 0.86 Bq kg−1 in apricot and olive, respectively, while in fresh samples they were 152.27 ± 2.12 and 1.99 ± 0.11 Bq kg−1 in dates and olive, respectively. The highest and lowest potassium contents were 489.81 and 6.42 mg/100gm in fresh dates and olives, respectively. Drupe and Tropical fruits, as a fruit family, typically had the highest level of 40K activity and potassium concentration, whereas pome fruits showed the lowest levels. Many of these commonly consumed fresh fruits with rich potassium and water contents are lowering hypertension and improving the hydration status (HS) in people's nutrition. The rate of potassium-40 and total potassium concentration intake for a single unit or portion of the fruits was calculated.

Effective atomic numbers and number, energy and dose albedos of different colored thermoplastic materials

This study was carried out to determine some distinctive features of thermoplastic materials used in radiotherapy. In this work, effective atomic numbers and number, energy and dose albedos of different colored thermoplastic samples (white, light green, green and blue) were determined for 59.54 keV gamma rays by using a high purity germanium detector. It is observed that the white thermoplastic sample has good reflectivity for gamma rays. The blue thermoplastic sample indicates superior shielding quantities since it has the lowest values of number, energy and dose albedos.

Measurement of the integrated cross section of 110Pd(γ,n)109mPd, 110Pd(γ,n)109gPd, and 110Pd(γ,x)108mRh reactions with 70 MeV bremsstrahlung

We measured the integrated cross sections of 110Pd(γ,n)109mPd, 110Pd(γ,n)109gPd and 110Pd(γ,x)108mRh reactions in the energy range from the reaction threshold to 70 MeV bremsstrahlung end-point energy. Measurements were performed by means of the activation method in combination with off-line γ-ray spectrometry. The induced activity of radionuclides was measured with a high-purity germanium (HPGe) detector and necessary corrections for γ-ray interferences were made. The integrated cross section of the studied reactions was measured relative to that of the monitor reaction 27Al(γ,2pn)24Na. Current results are compared with theoretical predictions using the TALYS-1.9 statistical nuclear model code. Calculations were performed using six different level density models in combination with eight γ-strength functions to determine which combinations best fit the experimental results. The present results are measured for the first time.

The 40Ar(d,p)41Ar cross section between 3–7 MeV

To determine the safety of using argon as a deuteron beam stopping material, the 40Ar(d,p)41Ar cross section was measured at average deuteron energies of 3.6 MeV, 5.5 MeV, and 7.0 MeV using an activation method. A 16-MeV deuteron beam produced by Lawrence Berkeley National Laboratory’s 88-Inch Cyclotron was degraded to each energy by nickel foils and the front wall of an aluminum gas chamber. The reduced-energy deuterons were used to activate a sample of natAr gas. After each irradiation, the gas chamber’s 41Ar activation was measured with a high-purity germanium detector. The cross sections measured were larger than a previous measurement by ∼40%.

Absolute quantification of 137Cs activity in spent nuclear fuel with calculated detector response function

ABSTRACT A new non-destructive method for evaluating 137Cs activity in spent nuclear fuels was proposed and experimentally demonstrated for physical measurements in burnup credit implementation. 137Cs activities were quantified using gamma ray measurements and numerical detector response simulations without reference fuels, in which 137Cs activities are well known. Fuel samples were obtained from a lead use assembly (LUA) irradiated in a commercial pressurized water reactor (PWR) up to 53 GWd/t. Gamma rays emitted from the samples were measured using a bismuth germinate (BGO) scintillation detector through a collimator attached to a hot cell. The detection efficiency of gamma rays with the detector was calculated using the PHITS particle transport calculation code considering the measurement geometry. The relative activities of 134Cs, 137Cs, and 154Eu in the sample were measured with a high-purity germanium (HPGe) detector for more accurate simulations of the detector response for the samples. The absolute efficiency of the detector was calibrated by measuring a standard gamma ray source in another geometry. 137Cs activity in the fuel samples was quantified using the measured count rate and detection efficiency. The quantified 137Cs activities agreed well with those estimated using the MVP-BURN depletion calculation code.

A high resolution γ-ray array for the pandora plasma trap

The measurement of β-decay rates in plasma, simulating stellar-like conditions, is of high interest for the investigation of radionuclides involved in nuclear astrophysics processes. In the new PANDORA plasma trap, to be built at the INFN—Laboratori Nazionali del Sud of Catania (Italy), the β-decay rates will be estimated by detecting the γ-rays emitted by the daughter nuclei trapped in the confined plasma. The present work describes the high efficiency High Purity Germanium (HPGe) detector array that will be placed around the magnetic trap for this purpose, as well as the front-end electronics and acquisition system suitable for the array operation in presence of a high counting rate background originating from Bremsstrahlung radiation.

An investigation on compatibility of experimental effective atomic numbers of some Fe–Ni alloys with those predicted by MCNP

In this work, effective atomic numbers of some Fe–Ni alloys were obtained experimentally by coherent and Compton scattering intensity ratios at scattering angle of 168° by using Americium-241 gamma rays (59.54 keV) and High Purity Germanium Detector (HPGe) detector. The experimental setup consisting of Am-241 and HPGe detector was simulated using the MCNP (Version 6.2) code. The intensity ratios of coherent and Compton scattering peaks of Cr, Mn, Fe, Co, Ni, Cu and Zn elements used for calibration were plotted as a function of their atomic numbers. The effective atomic numbers of the investigated alloys were determined by the interpolation method based on the coherent to Compton scattering ratio. Coherent to Compton intensity ratios of the alloys ranged from 1098.02 to 1165.47. The effective atomic number values obtained by MCNP simulation of the alloys were between 26.423 and 27.211, the experimentally effective atomic number values were between 26.524 and 27.382, and the theoretical effective atomic number values obtained with ZXCom were between 26.710 and 27.594. It is observed that the results obtained by the simulation method are in agreement with the experimental results and the theoretical results obtained with ZXCOM.

The effect of metal rate on the gamma shielding parameters of hydroxyapatite at medical treatment energies

The hydroxyapatite (HAp) is a kind of biomaterial which is used for bone treatment applications. We have scrutinized the gamma attenuation parameters such as such as the effective atomic number (Zeff), electron density (Nel), mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half value layer (HVL), tenth value layer (TVL) and mean free path (MFP) for only single liquid gamma source and a narrow beam geometry for the energy (medical treatment energy) ranging from 778 keV to 1408 keV (Eu-152) for the animal bone, iron, cobalt, copper, and zinc decorated Nano hydroxyapatite (nFeHAp, nCoHAp, nCuHAp, and nZnHAp) artificial bone powders. The gamma-rays were counted with using Ultra Low Energy Germanium detection system with a resolution 150 eV at 5,95 keV and a high purity germanium detector with a resolution of 1.85 keV at 1.33 MeV experimentally. The gamma ray attenuation parameters are calculated for the metal doped hydroxyapatite and compare with the animal bone. The results were compared with the output XCOM NIST data. While the mass absorption coefficient values for animal bone range from 0.08 to 0.05 at current energy levels, the values for metal-added artificial bone powders range from 0.07 to 0.05. While the linear absorption coefficient values for existing energy values for animal bone range from 0.04 to 0.02, they range from 0.03 to 0.02 for metal-added artificial bone powders. Mean free path values for real bone range from 24 to 36 at current energies, while half value layer values range from 16 to 25 and tenth value layer values range from 56 to 83. For metal-doped artificial bone powders, these parameters range from 26 to 35, 18 to 24, and 61 to 80, respectively. The results points that, the data of the gamma ray attenuation parameters are very close to the value of the animal bone due to the removal of calcium atoms from the structure when metal is added.

Natural Radionuclides in Bottled Mineral Waters Consumed in Turkey and Their Contribution to Radiation Dose.

Bottled natural mineral water (BMW) consumption in Turkey is increasing every year. Depending on the local geology from which the water is extracted, BMW could be enhanced with natural radionuclides. In this study, the activity concentrations of natural radionuclides in 58 BMW samples of 25 different brands marketed in Turkey were measured using a γ-ray spectrometer with high-purity germanium (HPGe) detector. The average activity concentrations of 226Ra, 228Ra, and 40K in BMW samples were found as 0.4, 0.5, and 4.3 Bq/L, respectively. The activity concentrations of 228Ra exceeded the WHO-recommended maximum permissible limit of 0.1 Bq/L for drinking water. The annual effective dose (AED) and excess lifetime cancer risk (LCR) caused by the ingestion of each BMW sample were estimated for adults to assess radiological risks using two different scenarios based on BMW consumption rates (150 and 13 L/y). All estimated total AEDs, except for two samples, were below the guidance dose level of 100 μSv/y recommended by the World Health Organization (WHO) and Turkish regulations for drinking water. For all BMW brands, 228Ra was found as the main contributor to the AEDs. The LCR values were lower than the acceptable value of 10–3 for radiological risks.

Influence of open cast mining on radiological health risk of agricultural soils around Adudu lead–zinc mine, Nasarawa State, Nigeria

Various fields of science have focused on the level of natural radionuclides in the environment since they are responsible for terrestrial background radiation exposure to members of the public. Gamma ray spectrometry with high purity germanium (HPGe) detector was used to measure the activity concentrations of natural radionuclides {238U (226Ra), 232Th and 40K} in one hundred and ten (110) composite soil samples collected from eleven (11) studied sites around lead (Pb)–zinc (Zn) mine. Result showed that the mean activities of 238U (226Ra), 232Th and 40K in the investigated soils varied between 28.49 ± 2.93–72.95 ± 7.07, 33.97 ± 4.09–105.78 ± 9.91 and 27.37 ± 1.87–853.16 ± 45.95 Bq/kg respectively. The activity concentrations of the analyzed natural radionuclides and their evaluated radiological health hazard parameters for soils around the mine, were above global average values and higher than those of control soil. The levels of 238U (226Ra), 232Th and 40K and the values of assessed radiological health hazard parameters for the control soil, were all lower than the global average values. This research showed that open cast mining of Pb–Zn in Adudu significantly increased the radiological health risk posed to the mine workers and community dwellers.

First results of the νGeN experiment on coherent elastic neutrino-nucleus scattering

The $\ensuremath{\nu}\mathrm{GeN}$ experiment is aimed to investigate neutrino properties using antineutrinos from the reactor of the Kalinin Nuclear Power Plant. The experimental setup is located at about 11 meters from the center of the 3.1 ${\mathrm{GW}}_{\mathrm{th}}$ reactor core. Scattering of the antineutrinos from the reactor is detected with low energy threshold high purity germanium detector. Passive and active shieldings are used to suppress all kinds of backgrounds coming from surrounding materials and cosmic radiation. The description of the experimental setup together with the first results is presented. The data taken in regimes with reactor on (94.50 days) and reactor off (47.09 days) have been compared. No significant difference between spectra of two datasets is observed, i.e., no positive signals for coherent elastic neutrino-nucleus scattering are detected. Under Standard Model assumptions about coherent neutrino scattering an upper limit on a quenching parameter $\mathrm{k}<0.26$ (90% CL) in germanium has been set.

Estimation of Residents Exposure Risks to Radiological Parameters in Some Building Materials in Nigeria

Some of the brands of tiles commonly available in the markets in Nigeria, which are used for building purposes, were analysed in order to estimate the concentration of naturally occurring radionuclides. The analysis was done with the aid of High-Purity Germanium (HPGe) detector. The results revealed that the average activity concentrations in the sample of tiles, cement and sand varied from 41 ± 4 to 96 ± 8.3, 27 ± 9.5 to 76.5 ± 2.5 and 140 ± 7.9 to 940 ± 19.2 Bqkg−1 for 232Th, 226Ra and 40K, respectively. The results obtained were used to determine the impact of these building materials on users. The radium equivalent activity (Raeq) ranged between 125 – 280 Bqkg−1 and were observed to be lower than 370 Bqkg−1 in all the samples tested, which is the recommended safe limit. Similarly, the absorbed dose rates were noted to vary from 51.00 – 122.52 nGyh−1. However, one of the samples examined showed a result of 122.52 nGyh− for the indoor absorbed dose rate (DR), which is higher than the internationally recommended safe value of 80 nGyh−1according to USEPA. The results revealed that the building materials investigated do not pose any danger to the end users.

Preparation of high purity germanium single crystal and analysis of dislocation density

High purity germanium detector plays an important role in the field of radiation detection. High purity germanium with 13N purity and dislocation density between 100 ~ 10 000 cm^-2 was successfully prepared through zone melting purification and single crystal growth. In the zone melting experiment, the self-made horizontal zone furnace is used to achieve the purification requirements through 20 ~ 50 times of zone melting in the environment of high-purity hydrogen. The single crystal is grown by Czochralski method along the [100] direction in high-purity hydrogen environment with effective length > 50 mm and effective diameter > 30 mm. The dislocation density measurement adopts the etching method. The acid etching solution is used to etch the crystal (100) surface and the number of the etch pits is counted. The results show that the dislocation densities at 25, 50 and 72 mm from the head of the single crystal are 2 537, 3 425 and 4 075 cm^-2 respectively. These results indicate that the dislocation density before 72 mm meets the requirements for the preparation of high-purity germanium detectors. The research can provide reference for the preparation of high purity germanium single crystal.

Assessment of Radioactivity Levels in Soil of Koya District in Kurdistan Region-Iraq Using High-purity Germanium Detector

Abstract: This study has been conducted to assess the 226Ra, 232Th, 40K and 137Cs radionuclides concentrations, through (5-10 and 15-25) cm-depth layers of the Koya district uncultivated soils, Erbil governorate, Kurdistan Region-Iraq, for 90 samples in 2018, using high-purity germanium detector (HpGe). As a result, the 5-10 cm layer concentrations have ranged from ‎3.8 ± 1.0 to 21.3 ± 0.3‎ (Bq.kg-1), 3‎.9 ± 0.3 to 36.2 ± 1.2 (Bq.kg-1), 95.0 ± 2.2 to 597.3 ± 8.9 (Bq.kg-1) and 0.0 to 42.7 ± 0.4 (Bq.kg-1) for 226Ra, 232Th‎, 40K and 137Cs, respectively. ‎In contrast, the 15-25 cm layer activities have shown lower values, where they have ranged from 2.6 ± 0.9 to 20.1 ± 0.3 (Bq.kg-1), 3.1 ± 0.3 to 35.3 ± 1.2 (Bq.kg-1), 545.0 ± 8.1 to 92.4 ± 2.1 (Bq.kg-1) and 0.0 to 29.1 ± 0.3 (Bq.kg-1), for 226Ra, 232Th‎, 40K and 137Cs, respectively. Moreover, the radiological parameters; namely, indoor and outdoor gamma absorbed dose rates, annual effective dose rates and excess life time cancer risks with internal and external hazard indices, have been estimated as follows: ‎(56.44, 29.22) ‎(nGy.h-1),) ‎0.28, ‎0.04) ‎‎(mSv.y-1)‎, ‎(0.97, 0.13) x 10-3, ‎0.20 and‎ 0.17, respectively. Fortunately, the results correspond with internationally healthy values. Keywords: Radioactivity, Soil, Effective dose, HPGe, Hazard, Koya.

Design and validation of a gamma-ray scanning system for measuring irradiated nuclear fuel

A prototype gamma-ray scanning system was designed to perform post-irradiation examination measurements of nuclear fuel. The system is composed of a coaxial high-purity germanium (HPGe) detector, a collimator, and mechanical positioning stages that translate the fuel sample across the front of the collimator. This paper documents the design process, modeling and the laboratory characterization performed to validate the system. The modeling of the system was done using the Monte Carlo N-Particle code with vendor-supplied design specifications, dimensional measurements, and X-ray radiographs of the HPGe detector. The characterization included measurements of calibrated radiation sources in different geometries, and calculations for absolute efficiency and dead time. Benchmark measurements were performed by scanning an irradiated fuel rodlet containing ten pellets of 4.9% enriched UO2 in zirconium alloy. These results were compared to simulated spectra to further help characterize the detector model. One goal of the system is to determine the number of fissions per gram of UO2 in the fuel; comparison of the results from this prototype system's assay of the irradiated fuel rodlet are in agreement with previously estimated results.

RADIOACTIVITY ASSESSMENT OF SURFACE SOIL IN THE VICINITY OF A URANIUM MINE IN MALAWI.

The activity concentrations of 238U, 232Th and 40K in the soil of areas surrounding the Kayelekera uranium mine were assessed. This study aims to provide a comprehensive profile of soil radioactivity distribution in the area surrounding the uranium mine to determine radiological hazards associated with mining and processing activities. Soil samples were analysed using gamma-ray spectrometry with a high-purity germanium detector. Mean specific activities of 238U, 232Th and 40K were 58.3±3.7, 40.3±0.3 and 590.9±63.9Bqkg-1, respectively. Results from this study have indicated changes in radioactivity levels of naturally occurring radioactive materials in the area surrounding the understudied mine, with certain areas close to the mine site showing elevated levels of 238U, highlighting the need for systematic and periodic monitoring.

MODELING AND OPTIMIZATION OF HPGE DETECTOR GC0518 USING MCNP5 CODE.

For precise modeling of a high purity germanium (HPGe) detector, detailed knowledge of its geometry is necessary. Unfortunately, some of the detector geometric parameters are often not available. This study suggests simple procedures for determining geometry without the need for radiography. The study considers the HPGe detector GC0518 manufactured by Mirion. The detector datasheet is available, but the uncertainties do not allow the detector to be modeled without additional corrections. The detector was modeled using MCNP5 code and the results were compared with calibration point sources and Marinelli beakers measurements. We also performed measurements to obtain information on the germanium dead layer, crystal holder shape, inner hole shape and radii of the crystal edges. Then the model was optimized according to the measurements. Finally, the full energy peak efficiencies were evaluated. The relative differences between the measured and calculated efficiencies are less than 4.5% for point sources and 5.4% for Marinelli beakers.

Activity Level of 238U, 232Th, 40K and Resultant Dose Rates in Soil and Some Commonly Cultivated Vegetables

This present study aims to determine the level of natural radionuclides of 40K, 238U and 232Th in soil samples and (Potato, Solanum tuberosum and Carrot, Daucus carota) samples and vegetables (Tomato, Solanum hycopersicum and Eggplant Solanum melongena) in Al- Mada'in district 30 km south east of Baghdad, Iraq. High purity germanium (HPGe) detector was used for measurement. The transfer factors, annual absorbed dose rate and the annual effective dose in the samples collected were determined. The results showed that the mean level of measured natural radionuclides were 362.6 ± 41.6 Bqkg-1, 184.7 ± 17.4 Bqkg-1, 191.9 ± 13.5 Bqkg-1, 120.3 ± 10.6 Bqkg-1 and 126.1 ± 11.7 Bqkg-1 for 40K; 19.67 ± 2.00 Bqkg-1, 4.70 ± 0.609 Bqkg-1, 5.43 ± 0.977 Bqkg-1, 3.30 ± 0.460 Bqkg-1 and 2.40 ± 0.701 Bqkg-1 for 238U and 12.34 ± 4.12 Bqkg-1, 3.77 ± 0.904 Bqkg-1, 4.54 ± 0.709 Bqkg-1, 3.51 ± 0.721 and 3.81 ± 0.796 Bqkg-1 for 232Th to soil, tomato, eggplant, potato and carrot samples respectively. The soil-to-tomato transfer factors were found to be 0.512, 0.242 and 0.344 for 40K, 238U and 232Th and soil-to-eggplant transfer factors were found to be 0.534, 0.279 and 0.408 for 40K, 238U and 232Th respectively. The soil-to-potato transfer factors were found to be 0.336, 0.170 and 0.320 for 40K, 238U and 232Th while the soil-to-carrot transfer factors were found to be 0.348, 0.122 and 0.309 for 40K, 238U and 232Th respectively. The mean absorbed dose rate was 30.0 ± 0.57 nGyh-1 and the mean annual outdoor effective dose was 55.2 mSvy-1. This present study's annual effective dose report was 91.6% of the world average value of 70.0 msvy-1 and 87.3% of Thi-Qar government, south Iraq state value of 39.9 msvy-1.

Search for Solar Axions via Axion-Photon Coupling with the Majorana Demonstrator.

Axions were originally proposed to explain the strong-CP problem in QCD. Through axion-photon coupling, the Sun could be a major source of axions, which could be measured in solid state detection experiments with enhancements due to coherent Primakoff-Bragg scattering. The Majorana Demonstrator experiment has searched for solar axions with a set of ^{76}Ge-enriched high purity germanium detectors using a 33kg-yr exposure collected between January, 2017 and November, 2019. A temporal-energy analysis gives a new limit on the axion-photon coupling as g_{aγ}<1.45×10^{-9} GeV^{-1} (95% confidence level) for axions with mass up to 100 eV/c^{2}. This improves laboratory-based limits between about 1 eV/c^{2} and 100 eV/c^{2}.