Efficiency HPGe Detector Research Articles

Characterization of neutron spectrum of polyethylene-moderated AmBe neutron source using a passive single-cylindrical neutron spectrometer

The changes in the neutron spectrum produced by the AmBe neutron source moderated in the polyethylene sphere need to be characterized. A passive single-moderator neutron spectrometer with indium foil activation neutron detector has been developed to characterize the neutron spectrum of an AmBe source inside a polyethylene sphere. The detector response function was calculated using the MCNPX 2.7 program with IRDFF-II nuclear data library. Measurements were conducted by placing the Single-Cylindrical Neutron Spectrometer (SCNS) on the outer surface of the sphere for 5 h. The 116mIn activity due to neutron activation in each indium foil was measured using a gamma spectrometer with an HPGe detector. By identifying the count value at the peak energy of 1294 KeV and considering an HPGe detector efficiency of 3.2% at the foil position 1 mm above the detector surface, the activity of 116mIn was obtained. The activity value of 116mIn from each indium foil was compared with the MCNPX simulation results. The neutron spectrum was unfolded using the UMG 3.3 program with activity data input of 116mIn for each foil and detector response. A neutron spectrum was obtained with a total neutron flux of 634 ± 60 n/cm2·s, consisting of 25% thermal neutrons, 16% epithermal neutrons, and 61% fast neutrons. When compared with the simulation results, the total neutron flux in the spectrum produced by SCNS-In showed only a small difference of 1%. Based on these neutron spectrum measurements, it was determined that placing the AmBe neutron source inside a 15″ diameter PE-sphere will reduce the fast neutron flux by 78%.

Improving instrumental neutron activation analysis detection limit using Monte Carlo simulation for lanthanides determination in Algerian phosphate

ABSTRACT Instrumental Neutron Activation Analysis (INAA) is one of the best methods to analyse Rare Earth Elements (REE) with a low detection limit in phosphate samples. Since most lanthanides emit gamma rays at the energy below 1000 keV, this energy range is affected by the Bremsstrahlung noise of beta emission produced by the 31P(n,γ)32P reaction, when the irradiation of the P2O5 composing the phosphate matrix (approximately 30%). This beta (β−) spectrum with a maximum energy of 1.71 MeV (average energy of 695 keV) affects the gamma spectrum and will reduce the detection limit significantly, other factors decrease the detection limit of lanthanides like neutron self-shielding and interference. In the present work, an analysis methodology based on optimising the measurement parameters of the INAA technique was implemented to improve the detection limits for the precise evaluation of lanthanide concentrations in Algerian phosphate deposits. The complete procedure was developed using a combination of a Monte Carlo simulation approach and experimental measurements. Two models were developed based on Monte Carlo simulation for the calibration of HPGe detector efficiency and the optimisation of type and filter thickness to reduce the beta spectrum (Bremsstrahlung) emitted by the 32P produced by neutron capture reaction 31P(n, γ) 32P. The developed model allowed a considerable improvement in the detection limit of the INAA technique and reduced the uncertainty in the lanthanide concentration. Finally, the methodology was applied to determine lanthanide elements in phosphate samples with good precision.

Steps Toward Optimizing HPGE Detector Efficiency in the Context of Low-Level Radioactivity Detection

"Different empirical and theoretical methods are used to precisely determine radionuclide activity concentrations. This study used Monte Carlo simulation MCNP5 code and EFFTRAN software (Efficiency Transfer) to determine the HPGe detector Full-Energy Peak (FEP) efficiency. A set of point sources (133Ba, 152Eu, 137Cs, 60Co, and 22Na) fixed on the top of the standard geometry plastic container were measured in order to obtain the calibration curve. Because of the importance of chemical composition parameters, the detector behavior due to different matrices was investigated. Experimental verification of the calibration was obtained using IAEA-TEL-2021-03 quality control water sample spiked with 152Eu and 133Ba, and the results were compared with reported results. A set of Certified Standard Reference samples were used for method validation. The obtained results were compared with the experimental results. The comparison clarified the advantages and disadvantages of both methods and their precision to demonstrate and suitable method for matrix types."

Calibrating GESPECOR model of computing the full-energy peak efficiency of coaxial high-purity germanium detectors by Monte Carlo simulation

In this work, a classical approach was used for calibrating the GESPECOR detector model for computing the full-energy peak efficiency of p-type coaxial HPGe detectors that is based on the use of linear least squares optimization. The key element of the work is the multiplicative model developed for approximating the values of the full-energy peak efficiency provided by GESPECOR code. It was linearized using the logarithmic transformation to allow an easy use of the linear least squares optimization. A procedure was also developed to estimate the optimal values of the parameters, describing the p-type coaxial HPGe detectors. Its application to a Canberra detector GC3018 showed that it is possible to determine accurate values of the full-energy peak efficiency computed by GESPECOR code using the optimized parameter values.

Determination of the full energy peak efficiency of HPGe detector for varying soil compositions and Marinelli beaker dimensions using Artificial Neural Networks

Natural radioactivity measurement is studying the radiation emitted naturally from any nature's components such as air, soil, water, etc. This field of study plays an important role in public health and safety management. Scientists and engineers can calculate the radiation doses received by inhabitants of a certain area by measuring the natural radioactivity in the same area. One of the main issues facing the standard measurement procedure is determining the appropriate volume of the sample to be taken from the area under investigation. The volume of the investigated sample affects the detection efficiency of the HPGe detector due to the self-shielding effect. In this work we show how using artificial neural networks can help in choosing the proper dimensions of the Marinelli beaker to be used in the detection process. We used the various compositions of soil as a case study. Results showed that artificial neural networks were capable of finding the relation between soil composition, Marinelli beaker dimensions, and gamma energy as inputs and the HPGe detection efficiency as output. The developed model's regression was 99% compared to the detection efficiency calculated using MCNP. This will help to have a better prediction of the detection efficiency of natural radioactivity measurements.

Corrections of HPGe detector efficiency curve due to true coincidence summing by program EFFTRAN and by Monte Carlo simulations

Standard reference sources, used for efficiency curve calibration of detector, often contain radionuclides with complex decay schemes (such as 60Co, 88Y, 152Eu …), introducing a potential problem in gamma-ray spectrometry, due to the appearance of coincidence summing of detected photons, in particular at a low source-detector distance. In this paper, a set of Monte Carlo simulations of an identical experimental setup were performed in order to obtain the efficiency curve of coaxial p-type HPGe detector for energy region (0–2) MeV, with the effect of true coincidence summing and without it. Obtained efficiency curves are compared with the experimental curve after applied EFFTRAN corrections. Fairly well agreement (between simulated and experimental curves with EFFTRAN corrections (with a relative deviation of 10%) proved the reliability of EFFTRAN corrections, as well as the possibility of Monte Carlo simulations for efficiency curve determination.

Efficiency stability of HPGe detectors under distinct count rates

In this work the reproducibility of the efficiency of different HPGe detectors was analyzed under a series of different conditions. The detectors studied were plugged either to a regular analogical amplifier or to a digital signal processing (DSP) device, in order to evaluate the possible differences between either setup. Detectors were inspected by performing a long series of sequential measurements with standard calibration sources, and comparing the standard deviation of the number of counts per second in each series to the uncertainty of the individual measurements. Detectors were also subjected to distinct count rates, in order to verify the possible experimental issues associated with this parameter. The results allow a discussion on the stability of the detectors’ efficiencies over a few days, the possible dependence with the count rate, and the estimation of the uncertainty related to the efficiency variation.

Novel integral expressions for computing the full energy peak efficiency of gamma spectrometry systems

A new theoretical approach was developed for computing the FEP efficiency of HPGe and scintillation detectors using the concept of probability function. Thus integral expressions for the FEP efficiency were developed using three probability functions. Starting from the integral expression of the FEP efficiency and using integral means and Chebyshev functional, new expressions of the FEP efficiency, detector response, and self-attenuation factors were obtained. Also, the new approach provides new insights useful for gamma spectrometry measurements. Two practical applications of this approach are described.

MCNP/Lab SOCS Model for Calculating the Absolute Full-Energy Peak Efficiency of HPGe Detector for Different Volume Sources

MCNP/Lab SOCS Model for Calculating the Absolute Full-Energy Peak Efficiency of HPGe Detector for Different Volume Sources

Optimization of Counting Time for Measurement of Ultra-low-level 238U and 232Th by 80% Relative Efficiency HPGe Detector

Optimization of Counting Time for Measurement of Ultra-low-level 238U and 232Th by 80% Relative Efficiency HPGe Detector

ESTIMATION OF RADIOLOGICAL EXPOSURE LEVELS IN A MINING AREA BASED ON 238U, 226Ra, 232Th and 40K ACTIVITY MEASUREMENTS: A CASE STUDY FOR BEYLIKOVA-SIVRIHISAR COMPLEX ORE SITE IN TURKEY.

The study estimated the radiological exposure levels in a mining area for miners in the Beylikova-Sivrihisar (Turkey) complex ore site containing 238U, 226Ra and 232Th. Sixty samples were collected from the study area based on a geologic map. The radionuclide activities were measured using a 78.5% efficient n-type HPGe detector. The measured mean activities were 1871±38Bqkg-1 for 238U, 1749±5Bqkg-1 for 226Ra, 3467±9Bqkg-1 for 232Th and 309±2Bqkg-1 for 40K. From the measured results, the external effective dose was calculated to be max. 3.80±0.03mSv y-1 (mean: 2.04±0.03mSv y-1) for inside gallery and max. 7.59±0.05mSv y-1 (mean: 4.08±0.05mSv y-1) for outdoor. Additionally, the external exposure index was calculated to be Hex=33.5±0.2(mean: 18.2±0.3) and internal exposure index to be Hin=45.9±0.3 (mean: 22.9±0.4). The results indicate that additional radiation protection measures should be taken during the mining process if an opencast mining is implemented in Beylikova complex ore deposit.

Efficient determination of HPGe [formula omitted]-ray efficiencies at high energies with ready-to-use simulation software

The full-energy-peak efficiency of HPGe detectors at γ-ray energies around 10MeV is not easily accessible with experimental methods. Monte-Carlo simulations with Geant4 can provide these efficiencies. G4Horus is a ready-to-use Geant4 application for the HORUS HPGe-detector array. Users can configure the modular parts to match their experiment with minimal knowledge of the simulation software and limited time commitment. In our case, knowing and implementing the geometry with high precision is the biggest challenge. To implement the different target chambers, we transform the existing CAD models to Geant4 geometry with CADMesh. We also found a large discrepancy between experimental and simulated efficiency for some older HPGe detectors, which could be remedied by introducing a large dead region around the inner core. This project is open source and available from https://github.com/janmayer/G4Horus (Mayer 2020). We invite everyone to adapt the project or adopt parts of the code for other projects.

Neutron self-shielding correction in application of k0-NAA standardization method to determine Mn content in manganese ores

In this study, it is aimed to investigate neutron self-shielding effect in application of k0-NAA standardization method to determine Mn contents in manganese ores. Because the neutron self-shielding correction factors are significant factors in application of k0-NAA method for large samples. To estimate these, several Mn-ore samples and Au monitor were irradiated separately in a 37 GBq 241Am–Be neutron source irradiation unit and then they were measured by using a 78.5% relative efficient HPGe detector. In this study, the sigmoid function approaches for calculation of Gth and Ge factors were applied for the right cylinder sample geometry at known elemental compositions in samples, determined by EDXRF technique with a 25 mm2 Silicon Drift Detector (SDD). The present results indicate that k0-NAA method is applicable successfully to determine Mn contents in Mn-ore samples providing that Gth and Ge factors are estimated accurately even if a low-flux isotopic neutron source is used.

Characterization of the Canberra BE5030 Broad Energy High Purity Germanium Detector by means of the GEANT4 Monte Carlo simulation package

The accurate determination of the efficiency of HPGe detectors is a challenging procedure due to possible self-attenuation phenomenaand/or coincidence summing effects. Both of these phenomena become important when close detection geometries and extended samples are considered. To deal with these features the simulation of HPGe detectors is used so as to calculate the corresponding correction factors, especially for those cases where low energy γ-ray are considered. Through the present work the Canberra BE5030 Broad Energy HPGe detector of the Enviromental Radioactivity Monitoring Department of Greek Atomic Energy Comission was simulated through the GEANT4 toolkit. Experimental efficiency and counting rate data were compared with the simulation results for different geometries of the detector so as to idetify the one for which the experimental data are better reproduced.

Study of the 191Ir(n,2n)190Ir cross section

The 191Ir(n,2n)190Ir cross section was measured by using of the activation technique at four neutron energies in the range 10.0-11.3 MeV. The quasimonoenergetic neutron beam was produced via the 2H(d,n)3He reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR ”Demokritos”. After the irradiations the induced activity of the samples was measured through a 56% relative efficiency HPGe detector. The cross section for the population of the second high spin (11−) isomeric state was measured along with the sum of the reaction cross section populating both the ground (4−) and the first isomeric state (1−). The experimental data will be combared to theoretical calculations in order to deduce information for the spin dependence of the level density parameters.

Cross section measurements of the 7 8Se(p,7)7 9Br and 8 0Se(p,7)8 1Br reactions

In beam cross section measurements of the 78Se(p,7)79Br and 80Se(p,7)81Br reactions have been carried out at Ep=1.4-3.5 MeV, by using high efficiency HPGe detectors with BGO shields for Compton background suppression. A preliminary analysis yielded total cross sections ranging from 10 μb to 3 mb. By means of the statistical compound nucleus theory of Hauser-Feshbach cross sections have also been calculated. A comparison between experimental data and theoretical predictions is presented.

Validation and Correction for 208Tl Activity to Assay 232Th in Equilibrium with Its Daughters

The natural radioactivity measurements and analysis of 232Th have been studied using γ-ray spectroscopy depending on its decay daughters in equilibrium; 208Tl of 583.19 keV, 228Ac of (911.2 and 968.97 keV) and 212Pb of 238.63 keV. When using these gamma transitions to calculate the 232Th specific activity, the 208Tl daughter of 583.19 keV gamma line with its 0.845 branching ratio gives activity of approximately 33.94% less than the other gamma transitions. This article is trying to explain and validate this difference and discrepancy that may encounter analysts during calculation of 232Th activity based on 208Tl (583.19 keV) gamma line. Very efficient HpGe detector was used to carry out this work. The MDA and figure of merit as functions of HpGe and energy sensitivity were calculated and tabulated. This issue was verified and validated using Black sand and natural environmental samples. A correction factor was proposed and applied on the 583 keV line of these samples that contain 232Th in equilibrium with its daughters to minimize and eliminate the abovementioned difference in the calculated 232Th specific activity.

Experimental and Monte Carlo determination of HPGe detector efficiency

Monte Carlo model has been developed using the GEANT code for calculation of the full energy peak efficiency of a HPGe detector operating in the Slovak Institute of Metrology. The model has been used for calculation of the HPGe detector efficiency for gamma-spectrometry measurements associated with the development of a national radon standard. The detector model was validated by comparison of simulated efficiencies with measured experimental values for point sources and for 450 mL Marinelli beaker. A reasonable, up to 5% agreement between the simulated and experimental results was achieved in the energy range from 100 to 1800 keV.

New measurement of thick target yield for narrow resonance at in the 13C()14N reaction**Project supported by the National Natural Science Foundation of China (Grant No. 11655003).

High energy γ-rays can be used in many fields, such as nuclear waste transmutation, flash photographics, and astrophysics. The 13C()14N resonance reaction was used to generate high energy and mono-energetic γ-rays in this work. The thick-target yield of the 9.17-MeV γ-ray from the resonance in this reaction was determined to be (4.7±0.4)/proton, which was measured by a HPGe detector. Meanwhile, the angular distribution of 9.17-MeV γ-ray was also determined. The absolute efficiency of HPGe detector was calibrated using 56Co and 152Eu sources with known radioactive activities and calculated by GEANT4 simulation.

Investigation hybrid MCNP/Angle model for calculating the absolute full-energy peak efficiency of HPGe detector

The absolute full energy peak efficiency values have been obtained by Monte Carlo MCNP5 code and semi-empirical ANGLE3 calibration software for a coaxial HPGe detector. The two calibration methods were combined to build a hybrid MCNP5/ANGLE3 model. The hybrid model can give efficiency calibrations values for various gamma-ray source shapes and geometries and then generate efficiency calibrations for new geometries instantly without needing new standards. The model has been checked experimentally and theoretically and then approved to cover the various gamma detection measurements.