Broad Energy Germanium Detector Research Articles

Design of a triggerless readout electronics system for CDEX-50

Direct detection of light-mass dark matter is a frontier topic in international physics research. The reduction of system threshold is important in order to improve the sensitivity of light-mass dark matter detection. The scientific goal of the China Dark Matter Experiment (CDEX) at Jinping Underground Laboratory in China is to detect WIMPs utilizing a high-purity germanium array detector. CDEX-10 achieved the most sensitive results in the 4 to 5 GeV/c 2 range. CDEX-50 aims to achieve an energy threshold of 100 eV, which significantly increases data bandwidth and complicates the implementation of noise reduction algorithms, thereby posing challenges to the readout electronics system. In this paper, a triggerless readout electronics system based on FPGA-GPU is designed for CDEX-50, which can achieve full energy range detection from 100 eV to 10 MeV. A verification prototype of a triggerless electronics system utilizing a Broad Energy Germanium (BEGe) detector has been developed to test the performance of high-bandwidth transmission and data processing. The results demonstrate that the bit error rate for the high-speed transmission link of the triggerless readout electronics system is below 1015. Furthermore, the FPGA-GPU transmission bandwidth, utilizing P2P DMA, achieves 100.2 Gbps, and the mean filter implemented on the GPU is capable of processing a 64 Gbps data stream in real-time. These results provide foundation for the design of the triggerless readout electronics system for CDEX-50.

Calibration for in vivo monitoring of thyroid of exposed population at risk of intakes of radioiodine isotopes due to a nuclear or radiological emergency

This work presents an improvement of the calibration of a broad energy germanium detector (BEGe) using age dependent neck-thyroid phantoms for thyroid monitoring of exposed individuals (workers and members of the public), allowing the detection and quantification of incorporated radioiodine isotopes in a nuclear medicine frame or in case of accident of a nuclear reactor.A BEGe detector was calibrated using a family of age-dependent thyroid-neck phantoms that simulate thyroids of 1, 5, 10, 15 year-old children and (male and female) adults, based in ICRP Publication 8 (ICRP, 2002) and ANSI 13.44 Standard (ANSI, 2014).The calibration of the BEGe detector for all neck phantoms was performed with the same counting geometry, centered under the BE Ge detector and at the same distance of 15 cm. Using same counting parameters allows to compare efficiency curves of thyroid monitoring depending with age. The in vivo measurements with the BE Ge detector allow to identify X rays and gamma emissions between 10 and 1000 keV with a great resolution and to quantify activities of radioiodine isotopes in the thyroid of exposed population.Calibration curves have been obtained for different sizes of the thyroid, depending with age. This study of counting efficiency using the main energies of the most important radioiodine isotopes result in accurate activity calculations. Detection limits were obtained for each radioiodine isotope, using blank phantoms of each age.

Optimization of a BEGe Detector Setup for Testing Quantum Foundations in the Underground LNGS Laboratory

In this work, we report on tests performed with an experimental apparatus prototype based on a broad-energy germanium detector aimed at investigating topical, foundational issues in quantum mechanics: i.e., possible violations of the spin-statistics connection and models of dynamical wave function collapse. Our recent phenomenological analyses demonstrated the importance of pushing the research of new physics signal, predicted in these fields, to an energy range below 10 keV. We describe the development of the dedicated data acquisition system and of the pulse shape discrimination algorithm, which have already allowed us to get a factor two improvement in the lower energy threshold. Future plans are discussed to further improve the lower energy threshold to the level of a few keV.

True coincidence summing correction for a BEGe detector in close geometry measurements

The true coincidence summing correction factor for a Broad Energy Germanium detector has been calculated at far and close geometry set-up using radioactive γ-ray sources. The correction factors were calculated using both experimental and analytical methods. Geant4 simulation was done to calculate the full-energy peak and total efficiencies of the detector. Standard, as well as fabricated mono-energetic γ-ray sources, were used for the γ-ray efficiency measurements. The simulated efficiencies of mono-energetic γ-ray sources were matched to the experimental γ-ray efficiencies by optimizing the detector parameters. The same parameters were used to obtain the full-energy peak and total efficiencies for γ-rays of current interest. Analytical and experimental correction factors were found to agree well with each other. The coincidence summing effect is found to be significant for source-to-detector distances less than 5 cm.

VADER: A novel decay station for actinide spectroscopy

A research programme focused on the study of the nuclear structure of actinide isotopes has recently been implemented at the IGISOL facility, University of Jyväskylä. Within this scope, a new decay station named VADER (Versatile Actinides DEcay spectRoscopy setup) has been developed and commissioned. The system consists of a compact array of silicon detectors, a liquid-nitrogen-cooled silicon lithium (Si(Li)) detector and three broad energy germanium detectors (BEGe), placed around a thin implantation carbon foil. The combined use of different detectors allows the measurement of α particles, conversion electrons and de-excitation γ rays in coincidence, enabling a full reconstruction of nuclear decay schemes. The measurement of basic nuclear decay observables provides a picture of the nuclear shell evolution in neutron-deficient actinides, and highlights the possible emergence of reflection-asymmetric shapes in the region.

Health risk assessment and statistical analysis of natural radioactivity in the uranium exploration area of Zabili, Chad

ABSTRACT The activity concentrations of natural radionuclides 226Ra, 232Th and 40K in 19 soil samples from Zabili uranium exploration area were measured using a low-background digital gamma-ray spectrometer equipped with broad energy germanium detector. The activity concentrations of 238U, 232Th, and 40K range from 16.5 to 1110.9 Bq.kg−1, 19.45 to 76.97 Bq.kg−1, and 3.28 to 839.5 Bq.kg−1, with their mean values of 478.0, 58.9, and 562.5, respectively. In addition, radiological hazard parameters from the activity concentrations obtained were assessed by estimating radium equivalent activity, external and internal hazard index, indoor and outdoor absorbed gamma dose rate and the corresponding annual effective dose, effective dose rate to different body organs and tissues, and excess lifetime cancer risk. Derived radiological hazard indices have been revised in accordance with relevant national and international legislation and guidelines. The radiological hazard parameter values were found to be above the relevant limit values for soils. In order to investigate the distribution of radionuclides and associated health hazard parameters in the study area, a statistical study was performed.

Determination of Naturally Occurring Radionuclides Concentration in Environmental Samples in West Kirby Area Using Gamma-Ray Spectroscopy

The purpose of this work is to investigate and evaluate the level of contamination of naturally occurring radionuclides in environmental soil samples collected at a place from West Kirby using gamma-ray spectroscopy. The Broad Energy Germanium (BEGe2825) detector has the ability to detect gamma-rays in the range of 3 keV-3MeV. This detector offers a very good resolution, low noise performance and almost ideal Gaussian shape in our analysis. Under our depth of interest of 0 – 48 cm, a total of six spectra were measured. From known values of gamma-ray energies, a calibrated curve was plotted. From the analysis, the mean activity concentration of naturally radionuclides of uranium-238, thorium-232 and potassium-40 obtained are 6.7 ± 0.1 Bq/kg, 5.6 ± 0.1Bq/kg and 398.2± 8.2 Bq/kg were found in the range of (5.37 ± 0.30- 8.86 ±0.40) Bq/kg, (4.37 ± 0.31- 8.72 ±0.35) Bq/kg and (384 ± 19 and 416 ± 21) Bq/kg respectively. Man-made radionuclides of americium-241 and cesium-137 mean activity concentrations are 4.3± 0.1 Bq/kg and 14.5 ± 0.3 Bq/kg were found in the range of (BDL: 5.95±0.32) Bq/kg and (6.66 ± 0.35- 29.2 ±1.5) Bq/kg respectively.

A rapid method for determining low concentrations of 210Pb in drinking water using MnO2 fibers

A rapid method for determining low activity concentrations of 210Pb in drinking water was developed and tested. The method consists of a few stages for sample preparation that involve passing 12 L of water through a column with acrylic fibers implanted with MnO2 (used to adsorb 210Pb). The MnO2 fibers are oven-dried, compressed and measured by a broad-energy germanium detector used to quantify 210Pb via its characteristic 46.5 keV γ-ray. The time taken for sample preparation is approximately 4 h and recovery factors for lead in tap water of 87 ± 3% were achieved. After a measurement duration of 4 h, the minimum detectable activity concentration reaches 0.02 Bq/L for 210Pb, being well below the respective limit for drinking water in Israel (0.2 Bq/L) as well as the value recommended by the World Health Organization (0.1 Bq/L). Furthermore, a measurement duration of 48 h provides a minimum detectable activity concentration of ∼0.006 Bq/L, which is similar in magnitude to other, well-established methods that rely on lengthy and rather complex procedures. Thus, the combination of MnO2 fibers and gamma-ray spectrometry may be attractive for routine use by analytical laboratories that monitor radioactivity in drinking water.

Search for neutrinoless double-beta decay of Ge76 with a natural broad energy germanium detector

A natural broad energy germanium (BEGe) detector is operated in the China Jinping Underground Laboratory (CJPL) for a feasibility study of building the next generation experiment of the neutrinoless double-beta (0{$\nu\beta\beta$}) decay of $^{76}$Ge. The setup of the prototype facility, characteristics of the BEGe detector, background reduction methods, and data analysis are described in this paper. A background index of 6.4$\times$10$^{-3}$ counts/(keV$\cdot$kg$\cdot$day) is achieved and 1.86 times lower than our previous result of the CDEX-1 detector. No signal is observed with an exposure of 186.4 kg$\cdot$day, thus a limit on the half life of $^{76}$Ge 0$\nu\beta\beta$ decay is set at T$_{1/2}^{0\nu}$ $>$ 5.62$\times$10$^{22}$ yr at 90% C.L.. The limit corresponds to an effective Majorana neutrino mass in the range of 4.6 $\sim$ 10.3 eV, dependent on the nuclear matrix elements.

Determination of natural radionuclides in phosphogypsum samples from phosphoric acid production industry in Senegal

In this study, the activity concentration of natural radionuclides (238U, 226Ra, 210Pb, 232Th, and 40K) in phosphogypsum were measured using a low-background digital gamma-ray spectrometer equipped with Broad Energy Germanium (BEGe) detector. The mean activity concentrations of 238U, 226Ra, 210Pb, and 232Th were found to be 88.5 ± 19.5 Bq kg−1, 879.6 ± 20.3 Bq kg−1, 755.4 ± 17.1 Bq kg−1, 4.5 ± 0.3 Bq kg−1, and below the detection limit respectively. The estimated radium equivalent activity was found to be higher than the world recommended value of 370 Bq kg−1 but is within the recommended limit of 2220 Bq kg−1 for the use of phosphogypsum in the construction of roads, bridges, and foundations of non-residential buildings. The total annual effective doses received by workers and members of the public were found to be lower than the annual limit of 1 mSv y−1, except for the scenario of a person living in a house built with building material containing phosphogypsum.

Determination of Uranium Isotopic Ratios by HRGS Using Various Efficiency Calibration Approaches

The effect of various efficiency calibration approaches on the value and source of the HRGS measurement uncertainty of 234U/238U, 235U/238U, 234U/235U isotopic ratios for the purposes of technological control, nuclear forensics, and environmental monitoring has been studied. The Canberra Broad Energy Germanium detector BEGe3830 and five samples of uranium certified reference materials CRM 969 and CRM 146 with a content of 235U/U ranging from 0.7 to 20.0 wt. % have been used. To calculate the uranium isotope ratios, the acquired gamma spectra were processed using: commercial MGAU (LLNL), FRAM (LANL), ISOCS software (Canberra/Mirion Technologies), based on intrinsic and absolute efficiency calibration approaches. It has been found that maximum relative biases, for the 234U/238U and 234U/235U isotopic ratios determined using the MGAU \ FRAM \ ISOCS software, are ~ 25 % \ ~ 10 % \ ~ 10 %, and the random uncertainty is varied within ± [18-25 % \ 2-15 % \ <=3 %], respectively. In the case of 234U/238U isotopic ratio determination using the MGAU \ FRAM \ ISOCS software, maximum relative biases come to ~ 3 % \ ~ 4 % \ ~ 1 %, and the random uncertainty values decrease to ± [1 % \ 1 % \ 1 %], respectively. In the present paper, we propose a combined intrinsic efficiency calibration approach with the use of the polynomial functions for the analytical description of the relation εrel.i(Ei). In this approach maximum relative biases, in the determination of the 234U/238U and 234U/235U isotopic ratios is 2.7 % at a random uncertainty of <= 1 %, and in the case of the 234U/238U ratio a maximum relative deviation is 0.5 % at a random uncertainty of <= 0.7 %.

New experimental limits on double-beta decay of osmium

Double-beta processes in 184Os and 192Os were searched for over 15 851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm3 ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in 184Os were set at the level of lim T 1/2 ∼ 1016–1017 years. In particular the 2ν2K and 2ν KL decays of 184Os to the ground state of 184W are restricted as T 1/2 ⩾ 3.0 × 1016 years and T 1/2 ⩾ 2.0 × 1016 years, respectively. A lower limit on the half-life for the double-beta decay of 192Os to the first excited level of 192Pt was set as lim T 1/2 = 2.0 × 1020 years at 90% confidence level

Assessment of natural radioactivity and its radiological hazards in several types of cement used in Senegal

In this study, the activity concentrations of 226Ra, 232Th and 40K in twenty cement samples of four types (CEM, CEM II, CEM III, and CEM IV) collected from building material suppliers in Senegal were measured using a low-background digital gamma-ray spectrometer equipped with broad energy germanium detector. The activity concentrations of 226Ra, 232Th and 40K varied from 7.1–150.3 Bq kg−1, 3.7–16.1 Bq kg−1, and 48.7–133.9 Bq kg−1, respectively. Also, possible radiological risks from the usage of these materials were assessed by estimating external and internal index, indoor absorbed gamma dose rate and the corresponding annual effective dose, effective dose rate to different body organs and tissus, and excess lifetime cancer risk. The estimated radiological hazard indices were revised in light of the relevant national and international legislation and guidance. The values of the radiological hazard indices were found to be within relevant all limit values for structural building materials.

Partial cross sections of 181Ta(n,γ) using BEGe detectors

Heavy nuclei are mainly synthesised by a sequence of neutron captures and β-decays. The corresponding neutron energies in the different astrophysical sites range from 1keV to 1MeV. By using the activation technique, small neutron capture cross sections can be studied. A sample is irradiated by a quasi-stellar neutron spectrum in order to produce radioactive isotopes. The decay of the radioactive nuclei can be detected by their characteristic gamma rays. For this purpose, sensitive experimental detector equipment is needed.Two Broad Energy Germanium Detectors (BEGe) were recently built up at the Goethe University Frankfurt. The first measurement of the partial neutron capture cross sections for the reaction 181Ta(n,γ) has been performed by using the activation technique.

Nuclear structure of $$^{181}$$Au studied via $$\upbeta ^+$$/EC decay of $$^{181}$$Hg at ISOLDE

The $$\upbeta ^+$$ /EC decay of mass separated samples of $$^{181}$$ Hg was studied employing the TATRA spectrometer at the ISOLDE facility at CERN. The decay scheme was constructed for the first time. A Broad Energy Germanium detector was used to achieve this by combination of high-gain $$\upgamma $$ -ray singles spectroscopy and $$\upgamma $$ – $$\upgamma $$ coincidences. The systematics of excited states associated with the 1 $$h_{11/2}$$ proton-hole configuration in odd-Au isotopes was extended.

Improving detection sensitivity of a low background BEGe spectrometer by pulse shape discrimination using rise-time ratio

To improve detection sensitivity for interesting radionuclides in measurements of environmental samples by Broad Energy Germanium detectors, the Pulse Shape Discrimination method using rise-time ratio is introduced. A certified soil sample and a typical squid-ash sample were measured by a well-shielded BEGe spectrometer. Minimum Detection Activities for the 722.9 keV and 949.8 keV peaks from the squid-ash sample were decreased by about 26% and 35% respectively. The method performs well especially when the main background comes from gamma radionuclides in samples.

Fluorescence-based method for estimating the dead layer thickness of a broad-energy germanium detector

A fluorescence-based method is proposed in this paper to estimate the front dead layer thickness of a broad-energy germanium detector. The germanium fluorescence was induced by the 57Co 14.4 keV gamma radiation incident on the dead layer. The count ratio between germanium fluorescence and the transmitted probe photons was experimentally measured and then compared with a series of Geant4 calculations for thickness determination. The method is sensitive to dead layer thickness owing to direct measurement of the thickness-dependent fluorescence and is independent of probe intensity and materials intervened between the source and the detector by using count ratio. The approach is anticipated to have a general application to surface studies of various types of germanium detectors.

Monte-Carlo simulations of the full-energy-peak efficiency for a broad-energy germanium detector—a comparison between GEANT4 and FLUKA

The detection efficiency of a broad-energy germanium detector was determined empirically and compared to predictions by the Monte-Carlo software GEANT4 and FLUKA . The considered source geometries were point-like, filter paper and a water beaker. Calculations were performed in the photon energy range of 30–1836 keV . Simulated detection efficiencies obtained from both Monte-Carlo software were found to be in a good agreement (typically <5%) with experimental results for the considered source geometries. A comparison between the detection efficiencies obtained with GEANT4 and FLUKA codes exhibited a good agreement with a robust average of approximately 1%.

Characterization of an electrically cooled BEGe detector till E[formula omitted] MeV

An electrically cooled Broad Energy Germanium (BEGe) detector has been characterized in the energy range Eγ∼0.122 - 7 MeV by utilizing the γ-rays emitted by a short-lived resonance state in 15O populated through 14N(p, γ) reaction and standard radioactive source (152Eu). The experimental results have been reproduced through simulations with GEANT4 code, including vendor specified detector geometry along with the detailed construction of the target holder flange, to delineate the effects of the holder at various energies and detector position. Later the efficiency with a bare point source has been simulated. It has been found that the electrically cooled BEGe detector is suitable for usage in the γ-ray spectroscopy as well as for the study of resonance phenomena in nuclear astrophysics.

Improved Cumulative Fission Yield Measurements with Fission Spectrum Neutrons on 238U

Two isotopically-characterized targets of high-purity (99.961±0.002%) 238U metal and a neutron dosimetry package were exposed to a pulsed neutron irradiation using the Godiva IV critical assembly at the National Criticality Experiments Research Center to measure the integral fission product yields produced in a Watt fission neutron-energy spectrum. Following irradiation, the fissioned targets were counted with two broad energy germanium detectors. Estimates of the total fissions for each target were made using measurements of well-known fission products. The total number of fissions in each target were then used to measure the fission yields of 33 fission products, 18 of which are published as new measurements. Twelve of the 18 isotopes were in agreement with ENDF/B-VIII.0 using the zeta test and treating ENDF/B-VIII.0 as the true mean: 84mBr, 93Y, 94Y, 104Tc, 134I, 135I, 138Xe, 141Ba, 142Ba, 142La, 146Ce, and 149Nd. The ENDF/B-VIII.0 fission yield for 139Ba was only slightly outside of 1-σ relative to the uncertainty measured in this work. Uncertainties for 5 fission product yields were markedly improved over those reported in ENDF/B-VIII.0: 128Sn, 129Sb, 130gSb, 131mTe, and 133I. The fission yields measured for 128Sn, 131mTe, and 133I were in good agreement with the ENDF/B-VIII.0 predicted fission yields. However, fission yields measurements of the isotopes 129Sb, and 130gSb deviated from the ENDF/B-VIII.0 value. Both of these isotopes reside near the doubly magic nuclear shell closures of 50 protons and 82 neutrons. These fission yields may be suppressed because of the odd-odd nuclear structure of 130gSb and the odd-even structure of 129Sb and isomer splitting. Comparisons to other recent work and a brief review with citations are included to support this conclusion.