High-purity Germanium Detector Research Articles

Investigation of using positronium and its annihilation for hypoxia PET imaging

Positron emission tomography (PET) is widely used for medical imaging to investigate the spatial distribution of pharmaceuticals labelled with positron emitters in patients. This study investigated the potential to perform three gamma (3γ) imaging based on ortho-positronium annihilation for assessment of tumour hypoxia. Evaluation of Oxygen deficiency is necessary to assure successful treatment. It was reported that PET imaging with a radioisotope could be used as molecular markers to detect tumour hypoxia. This method is based on the physics of 2γ annihilation. However, the 3γ annihilation yield is governed by the positronium formation as well as in quenching rates which could be used as a new PET molecular imaging modality. This study provides a method for the preparation of biological samples with different oxygen concentrations as well as developing a configuration system for the determination of the 3γ yield using high-purity germanium (HPGe) detectors to investigate the measurement of 3γ imaging. This study compares the decay rates in oxygen and nitrogen saturated samples of water and serum, the results show that 3γ annihilation with different oxygen concentrations could illustrate the oxygenation in biological models. Even though many diverse disciplines are involved in this work, the advantages and disadvantages of each possible technique have yet to be concisely summarized. This study sets out the background to the clinical applications of the 3γ PET technique and compares this non-invasive method with existing oxygen measurement devices.

Assessment the Natural Radioactivity of Radionuclides ( 226Ra, 232Th, 40K, and 137Cs) in Wheat Grain

This paper investigates the activity concentration of radionuclides (226Ra, 232Th, 40K and 137Cs) in the wheat grain samples using a high-purity germanium detector. Thirty-six wheat grain samples were collected from different locations of Koya City, Iraqi Kurdistan region. Average activity concentrations of 226Ra, 232Th and 40K in wheat grain are found to be 0.407 ± 0.097 Bq.kg-1 for 226Ra, 0.36 ± 0.14 Bq.kg-1 for 232Th and 109.25± 2.214 Bq.kg-1 for 40K, respectively. The measured activity concentrations for the radionuclides are compared with the reported data from other countries. In addition, the fallout radionuclide of 137Cs has no detection of in the wheat grain samples. The radium equivalent activity Raeq, internal and external hazard indices Hin and Hex, and annual gonadal dose equivalent are calculated for the measured samples. The total ingestion dose is 113.19 µSv.y-1, which is below the world average value of 290 µSv.y-1.

Assessment of solid mineral to soil radioactivity contamination index in selected mining sites and their radiological risk indices to the public

ABSTRACT This study examined the radioactivity levels of soil samples within selected solid mining sites in Nigeria using high-purity germanium (HpGe) detector. Sixty soil samples in all were collected from the 10 solid mineral mining sites investigated and six samples were collected as control samples from non-mining environment for analyses. The results of the activity concentration values obtained for 40K, 226Ra and 232Th are 100.22 Bq kg−1, 33.15 Bq kg−1 and 77.31 Bq kg−1, respectively. The 226Ra and 40K activities were found to be within the United Nation Scientific Committee on the Effects of Atomic Radiation acceptable permissible limit, but the 232Th mean value was above the permissible limit of 30 Bq kg−1 for the public. In comparison, 40K, 226Ra and 232Th soil samples mean activity concentrations were higher than the control soil samples values by 48.6%, 43.7% and 62.3%, respectively. The results of estimated radiation hazard indices indicate average values of 150.72 Bq kg−1, 68.40 nGyh−1 , 83.65 µSvy−1 and 454.70 µSvy−1 for the Radium Equivalent (Ra eq ), Absorbed Dose Rate (D), Dose Equivalent (AEDE) and Annual Gonadal Equivalent Dose (AGED), respectively. The mean values for External Hazard Indices (Hex, Hin), Representative Gamma index () and Excess Life Cancer Risk (ELCR) were 0.41, 0.50, 1.06 and 0.29 × 10−3, respectively. The statistical analysis shows positive skewness.

Production of microstructured BaZrO3 and Ba2P2O7-based polymer shields for protection against ionizing photons

Various highly effective shielding composites with low cost, light weight, and easy processing were fabricated by addition of various amounts of BaZrO3 and Ba2P2O7 to unsaturated polyester resin. The composites were analyzed by Fourier transform IR spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction. A high-purity germanium detector–based gamma spectrometer for experimental tests, WinXCom for theoretical calculations, and Geant4 for simulations were used to analyze the high-energy ionizing radiation shielding performances. The shielding results showed that there is good consistency (relative deviations less than 10%) among the three techniques. Addition of BaZrO3 and Ba2P2O7 as a filler in the composite enhances the radiation protection characteristics of the unsaturated polyester, and the composites with 20% BaZrO3 and 20% Ba2P2O7 had the most effective radiation shielding performance. Consequently, these innovative composites as radiation shielding materials are predicted to benefit medical physics and nuclear science applications.

Comparison of the X-ray tube spectrum measurement using BGO, NaI, LYSO, and HPGe detectors in a preclinical mini-CT scanner: Monte Carlo simulation and practical experiment

BackgroundIn diagnostic X-ray computed tomography (CT) imaging, some applications, such as dose measurement using the Monte Carlo method and material decomposition using dual/multi-energy approaches, rely on accurate knowledge of the energy spectrum of the X-ray beam. In this regard, X-ray detectors providing an accurate estimation of the X-ray spectrum could greatly impact the quality of dual/multi-energy CT imaging and patient-specific dosimetry. PurposeThe aim of this study is to estimate the intrinsic efficiency and energy resolution of different types of solid-state gamma-ray detectors in order to generate a precise dual-energy X-ray beam from the conventional x-ray tube using external X-ray filters. Materials and methodsThe X-ray spectrum of a clinical X-ray tube was experimentally measured using a high purity Germanium detector (HPGe) and the obtained spectrum validated by Monte Carlo (MC) simulations. The obtained X-ray spectrum from the experiment was employed to assess the energy resolution and detection efficiency of different inorganic scintillators and semiconductor-based solid-state detectors, namely HPGe, BGO, NaI, and LYSO, using MC simulations. The best performing detector was employed to experimentally create and measure a dual-energy X-ray spectrum through applying attenuating filters to the original X-ray beam. ResultsThe simulation results indicated 9.16% energy resolution for the HPGe detector wherein the full width-at-half-maximum (FWHM) of the energy resolution for the HPGe detector was about 1/3rd of the other inorganic detectors. The X-ray spectra estimated from the various source energies exhibited a good agreement between experimental and simulation results with a maximum difference of 6%. Owing to the high-energy discrimination power of the HPGe detector, a dual-energy X-ray spectrum was created and measured from the original X-ray spectrum using 0.5 and 4.5 mm Aluminum external filters, which involves 70 and 140 keV energy peaks with 8% overlap. ConclusionThe experimental measurements and MC simulations of the HPGe detector exhibited close agreement in high-energy resolution estimation of the X-ray spectrum. Given the accurate measurement of the X-ray spectrum with the HPGe detector, a dual-energy X-ray spectrum was generated with minimal energy overlap using external X-ray filters.

Assessment of a naturally occurring high background radiation area with elevated levels of thorium along coastal Odisha, India using radiometric methods

The present study evaluates the enrichment and distribution of radioelements along the eastern coast of India. India possesses the second largest reserve of thorium bearing monazite in the world, in terms of heavy minerals present primarily along its long coastline. Radioelement estimation of about 30 km long beach area along the eastern coast of India is reported and implications discussed. A total number of 822 data points were studied using a portable Geiger Muller counter, to estimate the variation of dose rates, due to the ambient radionuclides along two different trends. One was parallel (northeast-southwest) and the second one perpendicular to the coastline. Pre-selected samples from in-situ radiometric surveys on the heavy mineral placers were studied further, for quantitative estimation of the abundance of radioactive elements primarily uranium and thorium, using a High Purity Germanium detector. Radioelement concentration assessment of core samples (depth ~2 m), were studied from two different beaches. Radiological parameters like radium equivalent, annual effective doserate and absorbed dose rate has been calculated based on the 238U, 232Th and 40K concentrations. Heavy mineral placers along the shoreline indicate a very high thorium (avg - 2990.22 Bq kg−1) which is due to the extensive distribution indicative of monazite. The coastal area also exhibits relatively low uranium (avg - 319.1 Bq kg−1). Based on its high thorium concentration, the area can be considered as a high natural background radiation area. Based on the concentrations of uranium and thorium, the weathering conditions and depositional environment prevalent along the beach areas have been discussed.

Association of 241Am and 137Cs in finer size-fractioned saltmarsh sediments from north-west England, UK and potential health risk to coastal population

ABSTRACT This study provides an in-depth analysis of the relationship between radionuclide and particle size-class abundance through an investigation of radionuclide distribution in finer sediments within surface core samples collected from two contaminated upper saltmarsh areas of the Dee estuary and Biggar marsh in north-west England. The particle size fractionation (PSF) analysis was carried out following gravitational settling and pipette method to separate all samples into six size-fractioned groups ranging from 63 to <2 µm (very coarse silt to clay), and radioactivity analysis was performed using a well-type High Purity Germanium (HPGe) detector. The highest 241Am and 137Cs activities in PSF samples were found to be 291 ± 5 and 2071 ± 16 Bq kg−1, respectively, for the Dee estuary saltmarsh and 3832 ± 14 and 4840 ± 23 Bq kg−1, respectively, for Biggar saltmarsh and found in the clay fractions for both sites. Correlation of radioactivity concentration data of three size groups ranging from 63 to <2 µm (very coarse silt to clay) confirms a strong and increasing association of radioactivity with fine particles from coarse to fine clay-size particles. Also, examination of textural and radionuclide data of all bulk core and size-fractioned samples revealed that upper saltmarshes are made up of both contaminated and uncontaminated sediments. Furthermore, the annual outdoor external effective dose range for all short core data (0.001–0.11 mSv y−1) and for PSF sample data (0.001–0.08 mSv y−1) reveal that some values exceed the world average value of 0.07 mSv y−1as reported in UNSCEAR [43], for outdoor, which are non-negligible. Thus, the total annual external effective dose associated with existing contaminated saltmarsh sediments represents a possible health risk to saltmarsh users and coastal populations living nearby these saltmarshes.

Baseline radioactivity and associated radiological hazards in soils around a proposed nuclear power plant facility, South-South Nigeria

Increased concerns about human population exposure to increased ionizing radiations emanating from anthropogenic sources of radiation, as well as the associated environmental risk, have necessitated radioactivity baseline studies in many regions. This work based on standard procedures designed suite nuclear power plant (NPP) radiological monitoring plan was conducted to assess the radiological baseline of Itu, Nigeria (5ο10′0 N, 7°59′0 E). A total of 44 soil samples were collected and analyzed using High Purity Germanium detector. The average activity concentration values for soil samples were 47.98 ± 8 Bqkg−1226 for Ra, 15.15 ± 1 Bqkg−1 for 238U, 38.65 ± 6 Bqkg−1 for 232Th, and 41.55 ± 6 Bqkg−1for 4 K. These mean values were lower than the UN Scientific Committee on the effects of atomic radiation's world mean values of 33, 45, and 420 Bqkg−1 for 238U/226Ra, 232Th, and 4 K, respectively. The hazard indices calculated using the measured activity concentrations indicated 32.04 nGy/h, 0.042 mSv/yr, and 0.17 mSv/yr for mean GDR, outdoor, and indoor AEDE, respectively. In addition, the average radium equivalent resulting from terrestrial gamma of activity concentration was 113.94 Bqkg−1, with a mean ELCR of 0.15 × 10−3. These baseline data show that there is no substantial radiological concern for human health.

New method for the production of thin and stable, segmented n+ contacts in HPGe detectors

The realization of pulsed-laser diffused, thin n+ contacts on high purity germanium (HPGe) and their successful segmentation is described. The contacts have been obtained by a laser-induced diffusion of Sb atoms, deposited by sputtering on Ge surface, and then segmented by means of a photolithographic technique. Three small prototypes of gamma ray detectors have been implemented, using the same n+ contact (laser diffused Sb) but with three different geometries and a B implanted p+ contact. Electrical and detection properties of the prototypes have been characterized, showing low leakage currents and good spectroscopy data with different gamma-ray sources. The stability of the detector performance has also been tested subjecting one of the prototypes to a typical annealing treatment.

Determination the Natural Radioactivity Levels at Selected Regions in Al-Najaf Governorate

The natural radioactivity levels for radium(226Ra), thorium (232Th) and potassium (40K) have been determined in soil samples selected from different regions in Najaf governorate in Iraq. The samples were collected from the ground surface. Eight samples were measured by gamma ray spectroscopy using high purity germanium detector. The levelsof radionuclides concentrations in selected samples 232Th, 226Ra and 40K were in the range of (2.5±0.29 to 7.7±0.52) Bq/kg (6.3±0.43 to 16.4±1.9) Bq/kg and (31.5±3.4 to 204.1±11.9) Bq/kg for, respectively. The mean Radium Equivalent Activity, External and Internal Hazard Indices, the Absorbed Dose Rate in Air and the Annual Effective Doses Equivalent were studied and found these parameter are less than the reported values. Therefore, the radioactivity in the studied area in Najaf does not pose any radiological hazard to the general public.

Pulse-shape calculations and applications using the AGATAGeFEM software package

A software package for modeling segmented High-Purity Segmented Germanium detectors, AGATAGeFEM, is presented. The choices made for geometry implementation and the calculations of the electric and weighting fields are discussed and models used for charge-carrier velocities are described. Numerical integration of the charge-carrier transport equation is explained. The impact of noise and crosstalk on the achieved position resolution in AGATA detectors is investigated. The results suggest that crosstalk, as seen in the AGATA detectors, is of minor importance for the position resolution. The sensitivity of the pulse shapes to the parameters in the pulse-shape calculations is determined as a function of position in the detectors. Finally, AGATAGeFEM has been used to produce pulse-shape data bases for pulse-shape analyses of experimental data. The results with the new data base indicate improvement with respect to those with the standard AGATA data base. The AGATAGeFEM package sets itself apart with its high precision of the detector geometry description. This lends itself to numerical studies of the impact of segmentation lines and charge diffusion in the next step of code development.

β−γ spectroscopy of the Os195 nucleus

The $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ spectroscopy of $^{195}\mathrm{Os}$ nucleus was performed at the KEK isotope separation system (KISS). The radioactive isotope of $^{195}\mathrm{Os}$ was produced by the multinucleon transfer reactions of $^{136}\mathrm{Xe}$ beams and $^{198}\mathrm{Pt}$ target. The isotope of interest was separated and extracted by using KISS, which is an argon-gas-cell based laser ion source with a mass separator. Those extracted isotopes are implanted into an aluminized mylar tape, which is surrounded by the multisegmented proportional gas counter (MSPGC) and four clover-type high-purity germanium (HPGe) detectors for the $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ spectroscopy. 27 $\ensuremath{\gamma}$-ray peaks were observed in coincidence with internal conversion electrons and x rays detected by the MSPGC. 21 of them were identified as $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays of the $^{195}\mathrm{Os}$ ground state, where the energies of 19 $\ensuremath{\gamma}$-ray peaks agree with the literature values of transitions observed in $^{195}\mathrm{Ir}(n,\ensuremath{\gamma})$ reactions and two $\ensuremath{\gamma}$-ray peaks were newly found. The $\ensuremath{\beta}$-decay branching ratios of the $^{195}\mathrm{Os}$ ground state were deduced. The obtained log-$ft$ values range from $5.99(4)$ to $7.56(22)$, indicating all $\ensuremath{\beta}$-decay channels are the first forbidden transitions. It suggests that the spin-parity of the $^{195}\mathrm{Os}$ ground state is $3/{2}^{\ensuremath{-}}$, which is consistent with the systematical expectation. The $\ensuremath{\beta}$-decay half-life of the $^{195}\mathrm{Os}$ ground state was evaluated to be 6.5(4) min, which agrees well to the previously known value 6.5(11) min.

Production Cross-Section Measurements for Terbium Radionuclides of Medical Interest Produced in Tantalum Targets Irradiated by 0.3 to 1.7 GeV Protons and Corresponding Thick Target Yield Calculations.

This work presents the production cross-sections of Ce, Tb and Dy radionuclides produced by 300 MeV to 1.7 GeV proton-induced spallation reactions in thin tantalum targets as well as the related Thick Target production Yield (TTY) values and ratios. The motivation is to optimise the production of terbium radionuclides for medical applications and to find out at which energy the purity of the collection by mass separation would be highest. For that purpose, activation experiments were performed using the COSY synchrotron at FZ Jülich utilising the stacked-foils technique and γ spectrometry with high-purity germanium detectors. The Al-27(p,x)Na-24 reaction has been used as monitor reaction. All experimental data have been systematically compared with the existing literature.

Cross section measurements for (n,2n), (n,α), and (n,p) reactions on rhenium isotopes around 14 MeV neutrons and their theoretical calculations of excitation functions* *Supported by National Natural Science Foundation of China (11605099, 11575090)

Cross-section data of the 185Re(n,2n)184mRe, 185Re(n,2n)184gRe, 185Re(n,α)182m1+m2+gTa, 187Re(n, 2n)186g,(m)Re, 187Re(n,α)184Ta, and 187Re(n,p)187W reactions were measured at four neutron energies, namely 13.5, 14.1, 14.4, and 14.8 MeV, by means of the activation technique, relative to the reference cross-section values of the 93Nb(n,2n)92mNb reaction. The neutrons were generated from the T(d,n)4He reaction at the K-400 Neutron Generator at China Academy of Engineering Physics. The induced γ activities were measured using a high-resolution γ-ray spectrometer equipped with a coaxial high-purity germanium detector. The excitation functions of the six above-mentioned nuclear reactions at neutron energies from the threshold to 20 MeV were calculated by adopting the nuclear theoretical model program system Talys-1.9 with the relevant parameters properly adjusted. The measured cross sections were analyzed and compared with previous experiments conducted by other researchers, and with the evaluated data of BROND-3.1, ENDF/B-VIII.0, JEFF-3.3, and the theoretical values based on Talys-1.9. The new measured results agree with those of previous experiments and the theoretical excitation curve at the corresponding energies. The theoretical excitation curves based on Talys-1.9 generally match most of experimental data well.

Copper neutron transport libraries validation by means of a 252Cf standard neutron source

Copper is an important structural material in various nuclear energy applications, therefore the correct knowledge of copper cross sections is crucial. The presented paper deals with a validation of different copper transport libraries by means of activation of selected samples. An intense 252Cf(sf) source with a reference neutron spectrum was used as a neutron source. After irradiation, the samples were measured using a high purity germanium detector and the dosimeter reaction rates were inferred. These experimental data were compared with MCNP6 calculations using CENDL-3.1, JENDL-4.0, ENDF/B-VII.1, ENDF/B-VIII.0, JEFF-3.2 and JEFF-3.3 evaluated Cu transport libraries. The experiment specifically focuses on 58Ni(n,p)58Co, 93Nb(n,2n)92mNb, 197Au(n,g)198Au and 55Mn(n,g)56Mn dosimetry reactions. Evaluated activation cross sections of these dosimetric reactions were taken from the IRDFF-II library. The best library performance depends on the energy region of interest.

Effective atomic numbers of boron compounds obtained using Rayleigh to compton scattering intensity ratio

In this study, we measured the effective atomic numbers of some boron compounds (H4BNa, H3BO3, Na2B4O17H20, B4C, BN, NaCaB5O17H16, B2O3, Ca2B6O16H10, Zn2B6O14H6, TiB2, Fe2B, Ni3B, ZrB2, and LaBO3) by using 59.54 keV energy gamma rays emitted from an Am-241 radioactive source. Rayleigh and Compton scattering peaks were detected using a high purity germanium detector with a resolution of 182 eV at 5.9 keV. In addition, the effective atomic numbers of the boron compounds were theoretically calculated by using WinXCOM code. We concluded that the calibration curve obtained can be used for the qualitative analysis of compounds with effective atomic numbers in the range of 3.95 ≤ Z ≤ 54.15 because the experimental and theoretical effective atomic numbers were in very good agreement.

Time-resolved prompt-gamma activation analysis at spallation neutron sources and applications to cultural heritage, security, and radiation protection

The present and future developments of time-resolved prompt-gamma activation analysis (T-PGAA) at pulsed neutron sources is discussed in the framework of the successful history of neutron-activation techniques. A brief description of the state of the art and the most important user facilities using standard prompt-gamma activation analysis (PGAA) is provided. Then, we discuss the challenges and the opportunities for T-PGAA at pulsed neutron sources, and the potential impact for applications to cultural heritage, radiation protection, and security. We notice some inversions of trend needed for the further development of T-PGAA with epithermal and fast neutrons, such as the possibility to use fast and high-efficiency γ-ray scintillators with lower energy resolution (compared to usual high-purity germanium detectors) when the signal from neutron capture resonance is selected. We also suggest how detection systems often used in other fields, such as medical physics, can be of interest and inspiration also in the case of neutron-based investigations. Finally, we present new data of T-PGAA measurements on VESUVIO using neutron energies up to the keV using the scintillators available on the instrument, for samples of gold (of interest in cultural heritage), cadmium (for environmental safety), and tantalum (a material used in biomedical implants).

Characterizing the coaxial HPGe detector using Monte Carlo simulations and evolutionary algorithms

A standard procedure for characterizing the high-purity germanium detector (HPGe), manufactured by Canberra Industries Inc., is performed directly by the company using patented methods. However, the procedure is usually expensive and must be repeated because the characteristics of the HPGe crystal changes over time. In this work, the principles of a technique for use in obtaining and optimizing the detector characteristics based on a cost-effective procedure in a standard research laboratory were developed. The technique required the geometrical parameters of the detector to be determined as precisely as possible by the Monte Carlo method in parallel with the optimization process based on evolutionary algorithms. The development of this approach facilitated the modeling of the HPGe detector as a standardized procedure. The results would be also beneficial in the development of gamma spectrometers and/or their calibrations before routine measurements.

Estimation of Radionuclide (226Ra, 232Th and 40K) in Soil Granite Rock Mountains Phangan District, Surat Thani Province

The objective of this study were to analyze the specific activity of the natural radioactive nuclide of 226Ra, 232Th and 40K and to calculate the Radium equivalent activity (Raeq), the Internal hazard index (Hin), the External hazard index (Hex), the Gamma-absorbed dose rate (D) and the Annual external effective dose rate (E) in the 20 soil samples from Koh Phangan District, Surat Thani Province by using gamma-ray spectrometer with a high purity germanium detector (HPGe). The results show that the specific activity of radioactive nuclides in many samples were higher than Thailand and the global average values. In addition, the Radium equivalent activity (Raeq), the Internal hazard index (Hin), the external hazard index (Hex) and the gamma-absorbed dose rate (D) were higher than the UNSCEAR criterion (2000). The present study found that the radioactivity may affect the health of people living in that area.

Gamma ray characterization of the albedo of atmospheric dust from Southeast Anatolia, Turkey

Atmospheric dust samples were collected using PM10 (particulate matter less than 10 µm) and PM2.5 (particulate matter less than 2.5 µm) filters in 2019 from Southeast Anatolia, Turkey. The direction and source of the dust were determined using the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite view and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. X-ray diffraction (XRD) has shown the presence of calcite and quartz as major components of the aerosol dust. The albedo parameters of atmospheric dust were experimentally determined for 59.54 keV photons emitted from an Am-241 source. Compton and coherent scattered peaks were acquired with a high purity germanium detector. The sample collected in May has a higher density than in June. The sample density at PM10 is larger than PM2.5 and the density of 23 June 2019 is smaller than for the other dates. The albedo parameters of the filter in June and May for PM10 are greater than those of PM2.5. The dust of larger particles is more reflected by the high-energy photons.