High Resolution HPGe Detector Research Articles

Fission Product Yield Study of 235U, 238U and 239Pu Using Dual-Fission Ionization Chambers

To resolve long-standing differences between LANL and LLNL regarding the correct fission basis for analysis of nuclear test data [M.B. Chadwick et al., Nucl. Data Sheets 111, 2891 (2010); H. Selby et al., Nucl. Data Sheets 111, 2891 (2010)], a collaboration between TUNL/LANL/LLNL has been established to perform high-precision measurements of neutron induced fission product yields. The main goal is to make a definitive statement about the energy dependence of the fission yields to an accuracy better than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed the design, fabrication and testing of three dual-fission chambers dedicated to 235U, 238U, and 239Pu. The dual-fission chambers were used to make measurements of the fission product activity relative to the total fission rate, as well as for high-precision absolute fission yield measurements. The activation method was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and 14.5 MeV were produced via the 2H(d,n)3He reaction, and for neutrons at 14.8 MeV, the 3H(d,n)4He reaction was used. After activation, the induced γ-ray activity of the fission products was measured for two months using high-resolution HPGe detectors in a low-background environment. Results for the yield of seven fission fragments of 235U, 238U, and 239Pu and a comparison to available data at other energies are reported. For the first time results are available for neutron energies between 2 and 14 MeV.

Cross sections of fusion and transfer reactions in interactions between 3He and Pt and 197Au nuclei in the subbarrier energy region

The reactions of complete and incomplete fusion, along with nucleon transfer reactions in the range of 3He energies from 10 to 24.5 MeV, are investigated by irradiating gold and platinum targets with an accelerated 3He ion beam on the U-120M cyclotron at the Institute of Nuclear Physics, Czech Academy of Sciences, Řež. Activation is used to determine the yield of nuclides resulting from nuclear reactions. The γ-activity induced in the targets is measured using a with high-resolution HPGe detector. Despite the low binding energy of 3He and the reactions with positive Q values, the measured cross sections of fusion reactions exhibit no specific features, compared to reactions conducted using beams of other light stable particles. Transfer neutron reactions in the subbarrier energy region have relatively high cross sections. These cross sections continue to grow as the energy of 3He rises. When a neutron is captured by a nucleus of 3He, the cross sections of these reactions reach their maximum values in the Coulomb barrier region.

Measurement of effective atomic number of gunshot residues using scattering of gamma rays

Better understanding of gunshot residues and the major elemental composition would be valuable to forensic scientists for their analysis work and interpretation of results. In the present work, the effective atomic numbers of gunshot residues (cartridge case, bullet core, bullet jacket and gunpowder) were analyzed using energy dispersive X-ray analysis (EDX). The scattering of 59.54keV gamma rays is studied using a high-resolution HPGe detector. The experiment is performed on various elements with atomic number in the 4≤Z≤82. The intensity ratio of coherent to Compton scattered peaks, corrected for photo-peak efficiency of gamma detector and absorption of photons in the sample and air, is plotted as a function of atomic number and constituted a best-fit-curve. From this fit-curve, the respective effective atomic numbers of gunshot residues are determined.

Radiological assessment of the surface soil of Bangladesh

The specific activities of 232Th, 238U, 40K, and 137Cs in undisturbed surface soil at 56 locations of Bangladesh, covering its entire area, were measured using high resolution HPGe detector. The mean specific activity concentrations of the mentioned radionuclides were respectively found to be 83.56 ? 17.96 Bq/kg, 44.35 ? 12.65 Bq/kg, 630.89 ? 173.85 Bq/kg, and 5.37 ? ? 4.87 Bq/kg. A good correlation between the activities of 232Th and 238U was found. The radiological parameters namely radium equivalent activity, representative level index, external hazard index, internal hazard index, absorbed dose rate, and effective annual outdoor dose rate due to the natural radionuclides were also calculated. The average values of the mentioned parameters were found to be 212.26 ? 43.93 Bq/kg, 1.55 ? 0.32 Bq/kg, 0.29 ? 0.06, 0.69 ? 0.15, 97.27 ? 20.03 nGy/h, and 119.37 ? 24.58 mSv/y, respectively. The radiation dose levels at the points of sample collection were also measured by a portable radiation dose rate-meter. The average value of the outdoor dose rate was found to be 0.20 ? 0.07 mSv/h ranging from 0.16 ? 0.02 mSv/h to 0.28 ? 0.04 mSv/h. The distributions of natural radionuclides were found to be normal. The concentration levels of different radionuclides were comparable to the corresponding reported values of the soil of different countries.

Determining the water content in concrete by gamma scattering method

A gamma scattering method for determining the water content in concrete sample applicable to any porous building material is described. The experimental setup consists of collimated 137Cs radioactive source and a high resolution HPGe detector based energy dispersive gamma ray spectrometer. Concrete samples of uniform density ≈2.4g/cm3 are chosen for the study and the scattered intensities found to vary with the amount of water present in the specimen. The scattered intensities are corrected for attenuation effects and the results obtained with reference to a dry sample are compared with those obtained by gravimetrical and gamma transmission methods. A good agreement is seen between gamma scattering results and those obtained by gravimetric and transmission methods within accuracy of 6% and <2% change in water content can be detected.

Cross sections for production of 43Sc, 44Sc, and 46Sc isotopes in the 45Sc + 3He reaction

Reactions 45Sc(3He, αn)43Sc, 45Sc(3He, α)44Sc, and 45Sc(3He, 2p)46Sc, resulting from the irradiation of scandium targets with a beam of 3He ions with energy from 5 to 24 MeV, are investigated in experiments on the U120M cyclotron of the Nuclear Physics Institute (Rez, Czech Republic). The activation technique is used to find the yield of the produced Sc isotopes. The induced γ activity in the targets is measured using a high-resolution HPGe detector. Despite the low binding energy of 3He and positive reaction Q values, which leads to formation of the 44Sc and 46Sc isotopes, the behavior of the excitation functions for the formation of these isotopes differs from the behavior of the excitation function for deuterons. Scandium-44 formation cross sections reach their maximum at the reaction Coulomb barrier. This is because not only 44Sc but also a stable 4He nucleus is formed in the reaction.

Measurement of the effective atomic number of FexCr1−x and FexNix alloys using scattering of gamma rays

In the present work, to determine the effective atomic number of alloys such as Fe0.5Cr0.5, Fe0.7Cr0.3, Fe0.8Cr0.2, Fe0.9Cr0.1, Fe0.2Ni0.8, Fe0.3Ni0.7, Fe0.5Ni0.5, Fe0.6Ni0.4, Fe0.7Ni0.3 and Fe0.8Ni0.2 the scattering of 59.54keV gamma rays is studied using a high-resolution HPGe detector with a resolution of 182eV at 5.9keV and placed at 167o. The experiment is performed on various elements with atomic number satisfying, 4⩽Z⩽82, for 59.54keV gamma rays from a 5Ci 241Am annular radioactive source. The intensity ratio of Rayleigh to Compton scattered peaks, corrected for photo-peak efficiency of gamma detector and absorption of photons in the sample and air, is plotted as function of atomic number and constituted a best fit-curve. From this fit-curve, the respective effective atomic numbers to samples of alloys are determined. Also, the effective atomic numbers of alloys have been calculated by using the theoretical mass attenuation coefficients. The agreement of measured values of effective atomic numbers with theoretical calculations is quite satisfactory.

Cross sections of 43Sc, 44Sc, 46Sc isotopes formed in the 45Sc + 3He reaction

Reactions 45Sc(3He, αn)43Sc, 45Sc(3He, α)44Sc and 45Sc(3He, 2p)46Sc in the 3He energy range of 5 to 24 MeV are investigated in experiments performed with a 3He ion beam during the irradiation of U-120M cyclotron scandium targets. Activation is used to determine the yield of nascent Sc isotopes. The γ activity induced in targets is measured using a high-resolution HPGe detector. The character of the excitation function changes during the formation of these ions and differs from the excitation functions for deuterons, despite the low bond energy of 3He and the positive values of the Q reactions leading to the formation of 44Sc and 46Sc isotopes. The cross sections of 44Sc formation reach their maximum value at the Coulomb barrier of the reaction, due to the stable 4He nucleus that accompanies the formation of 44Sc. The contribution from different reaction mechanisms to the cross sections of 43Sc, 44Sc, and 46Sc isotope formation are considered.

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The existing Nuclear Resonance Fluorescence (NRF) setup at the HIγS facility at the Triangle Universities Nuclear Laboratory at Duke University has been extended in order to perform γ–γ coincidence experiments. The new setup combines large volume LaBr3:Ce detectors and high resolution HPGe detectors in a very close geometry to offer high efficiency, high energy resolution as well as high count rate capabilities at the same time. The combination of a highly efficient γ-ray spectroscopy setup with the mono-energetic high-intensity photon beam of HIγS provides a worldwide unique experimental facility to investigate the γ-decay pattern of dipole excitations in atomic nuclei. The performance of the new setup has been assessed by studying the nucleus 32S at 8.125MeV beam energy. The relative γ-decay branching ratio from the 1+ level at 8125.4keV to the first excited 2+ state was determined to 15.7(3)%.

Determination of the K absorption edge energy of Ho in element and its compounds using the bremsstrahlung technique

The K shell binding energies of Ho in element and in compounds Ho2O3 and HoF3 have been measured for the first time by adopting a novel method. The method involves a weak beta source, an external bremsstrahlung (EB) converter, element and compound targets and a high-resolution HPGe detector coupled to a 16K multichannel analyser. A spectrum of continuous EB photons, produced by the interaction of beta particles from a 90Sr–90Y radioactive source with an iron foil, is allowed to pass through the element and compound targets of Ho. The spectrum of transmitted EB photons is measured with a high-resolution HPGe detector spectrometer. The transmitted spectrum shows a sudden drop in intensity at K shell binding energy of the target. Such a sudden drop, which is essentially due to the onset of the K shell photoelectric effect, has been used to determine the K shell binding energy of Ho in element. The K shell binding energies of Ho in Ho2O3 and HoF3 compounds have also been determined using the same technique. From these data, the chemical shift in the K shell binding energy has been measured. It is found to be positive for Ho2O3 and negative for HoF3, indicating the dependence of the chemical shift on the crystal structure.

Measurement of real and imaginary form factors of silver atom using a high resolution HPGe detector

The real and imaginary form factors of silver atom have been determined by using EDXRF method. The K x-ray photons in the energy range from 8.62 keV to 52.18 keV are generated by sending 59.56 keV gamma photons from <formula>^{241}</formula>Am radioactive source on various targets. These K x-ray photons are transmitted through silver foils of suitable thickness. The incident and transmitted K x-ray photon intensities have been measured with a high resolution HPGe detector which is coupled to 16K MCA. The photoelectric cross sections at different K x-ray energies have been determined by measuring the intensities of the incident and transmitted x-ray photons. From these photoelectric cross section values, the imaginary form factors and the real form factors have been determined at various photon energies. Measured imaginary and real form factor values have been compared with theoretical values predicted by XCOM [23] and FFAST [24].

Determination of K shell parameters of silver using high resolution HPGe detector spectrometer

The K shell parameters such as K shell photoelectric cross-section at K shell binding energy, K shell jump ratio, K shell jump factor, the Davisson- Kirchner ratio and K shell oscillator strength of silver have been determined using high resolution HPGe detector coupled to 16K multichannel analyser. In this method the K X-ray photons in the energy region from 8 to 52 keV are generated by sending 59.56 keV gamma photons from Am-241 source on various targets. These X-ray photons are allowed to pass through a silver foil in good geometry arrangement. By measuring the intensities of incident and transmitted photons, the mass attenuation coefficients are determined at various X-ray energies. Measured mass attenuation coefficient around K shell binding energy and K shell parameters have been compared with values predicted by XCOM and FFAST and with other experimental values.

Decay spectroscopy for nuclear astrophysics: β- and β-delayed proton decay

In several radiative proton capture reactions important in novae and XRBs, the resonant parts play the capital role. We use decay spectroscopy techniques to find these resonances and study their properties. We have developed techniques to measure beta- and beta-delayed proton decay of sd-shell, proton-rich nuclei produced and separated with the MARS recoil spectrometer of Texas A&M University. The short-lived radioactive species are produced in-flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. This allows us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. At the same time we measure gamma-rays up to 8 MeV with high resolution HPGe detectors. We have studied the decay of 23Al, 27P, 31Cl, all important for understanding explosive H-burning in novae. The technique has shown a remarkable selectivity to beta-delayed charged-particle emission and works even at radioactive beam rates of a few pps. The states populated are resonances for the radiative proton capture reactions 22Na(p,γ)23Mg (crucial for the depletion of 22Na in novae), 26mAl(p,γ)27Si and 30P(p,γ)31S (bottleneck in novae and XRB burning), respectively. Lastly, results with a new detector that allowed us to measure down to about 80 keV proton energy are announced.

A comparative study of232Th and238U activity estimation in soil samples by gamma spectrometry and neutron activation analysis technique

Neutron activation analysis (NAA) is a well-established analytical technique. It has many advantages as compared to the other commonly used techniques. NAA can be performed in a variety of ways depending on the element, its activity level in the sample, interference from the sample matrix and other elements, etc., This technique is used to get high analytical sensitivity and low detection limits (ppm to ppb). The high sensitivity is due to the irradiation at high neutron flux available from the research reactors and the activity measurement is done using high resolution HPGe detectors. In this paper, the activity estimation of soil samples using neutron activation and direct gamma spectrometry methods are compared. Even though the weights of samples considered and samples preparation methods are different for these two methods, the estimated activity values are comparable.

The 25Mg(p, γ)26Al reaction at low astrophysical energies

In the present work we report on a new measurement of resonance strengths ωγ in the reaction 25Mg(p, γ)26Al at Ecm=92 and 189 keV. This study was performed at the LUNA facility in the Gran Sasso underground laboratory using a 4π BGO summing crystal. For the first time the 92 keV resonance was directly observed and a resonance strength ωγ=(2.9±0.6)×10−10 eV was determined. Additionally, the γ-ray branchings and strength of the 189 keV resonance were studied with a high resolution HPGe detector yielding an ωγ value in agreement with the BGO measurement, but 20% larger compared to previous works.

Measurement of K absorption edge energies of silver and tin targets using a weak beta source

AbstractK absorption edge energies of Ag and Sn elements have been determined by using a weak beta source. In this method, the beta particles from a 90Sr90Y beta source interact with an iron foil to produce the external bremsstrahlung (EB) photons. The spectrum of EB photons is passed through the elemental target and the spectrum of transmitted photons is recorded with a high resolution HPGe detector spectrometer coupled to 16K multichannel analyzer. The recorded transmitted EB spectrum shows a sharp decrease in intensity at the K shell binding energy of elemental target. Such a sharp decrease region, which is corrected for Kβ′2 contribution, has been used to determine the K absorption edge energies of Ag and Sn elemental targets. The measured values have been compared with theoretical and experimental values. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Radiological monitoring: terrestrial natural radionuclides in Kinta District, Perak, Malaysia

Natural background gamma radiation and radioactivity concentrations were investigated from 2003 to 2005 in Kinta District, Perak, Malaysia. Sample locations were distant from any ‘amang’ processing plants. The external gamma dose rates ranged from 39 to 1039 nGy h −1. The mean external gamma dose rate was 222 ± 191 nGy h −1. Small areas of relatively enhanced activity were located having external gamma dose rates of up to 1039 ± 104 nGy h −1. The activity concentrations of 238U, 232Th and 40K were analyzed by using a high-resolution co-axial HPGe detector system. The activity concentration ranges were 12–426 Bq kg −1 for 238U, 19–1377 Bq kg −1 for 232Th and <19–2204 Bq kg −1 for 40 K. Based on the radioactivity levels determined, the gamma-absorbed dose rates in air at 1 m above the ground were calculated. The calculated dose rates and measured dose rates had a good correlation coefficient, R of 0.94. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the gamma-absorbed dose rate and the mean population weighted dose rate were calculated. An isodose map for the Kinta District was also produced.

Activity levels of gamma-emitters in Argentinean cow milk

With the aim of contributing to the establishment of baselines for natural and man-made radioisotopes, the concentration of gamma-emitter radionuclides was determined in a set of commercial and dairy farm liquid cow milk produced in the most important production regions of Argentina using a gamma-ray spectrometer with a high-resolution HPGe detector. For comparison, samples from Chile and Uruguay were also analyzed. The main detected activity corresponded to 40K, while the activities of elements of the natural chains were below the detection limit. The determined 40K average activity for the Argentinean milk was 60 Bq/L. Traces of the anthropogenic radionuclide 137Cs were observed only in the Chilean milk sample.

Mass attenuation coefficient of chromium and manganese compounds around absorption edge

The total mass attenuation coefficient for Potassium dichromate, Potassium chromate and Manganese acetate compounds are measured at different photon energies 5.895, 6.404, 6.490, 7.058, 8.041 and 14.390 keV using Fe-55, Co-57 and 241Am source with Copper target, radioactive sources. The photon intensity is analyzed using a high resolution HPGe detector system coupled to MCA under good geometrical arrangement. The obtained values of mass attenuation coefficient values are compared with theoretical values. This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 5-28%.

Measurement of theAm241(n,2n) reaction cross section from 7.6 MeV to 14.5 MeV

The (n,2n) cross section of the radioactive isotope Am241 (T1/2=432.6 y) has been measured in the incident neutron energy range from 7.6 to 14.5 MeV in steps of a few MeV using the activation technique. Monoenergetic neutron beams were produced via the H2(d,n)He3 reaction by bombarding a pressurized deuterium gas cell with an energetic deuteron beam at the TUNL 10-MV Van de Graaff accelerator facility. The induced γ-ray activity of Am240 was measured with high-resolution HPGe detectors. The cross section was determined relative to Al, Ni, and Au neutron activation monitor foils, measured in the same geometry. Good agreement is obtained with previous measurements at around 9 and 14 MeV, whereas for a large discrepancy is observed when our data are compared to those reported by Perdikakis et al. near 11 MeV. Very good agreement is found with the END-B/VII evaluation, whereas the JENDL-3.3 evaluation is in fair agreement with our data.Received 5 March 2008DOI:https://doi.org/10.1103/PhysRevC.77.054610©2008 American Physical Society