High Resolution HPGe Detector Research Articles

Arsenic and heavy metal concentrations in surface soils and vegetables of Feni district in Bangladesh

An investigation of various heavy metals including the arsenic (As) poisoning in soils and vegetables in five upazillas under Feni district of Bangladesh was performed by neutron activation technique using the neutron irradiation facilities of TRIGA MARK II research reactor at Bangladesh Atomic Energy Research Establishment (BAERE), Savar, Dhaka. A total of 30 samples (15 surface soils and 15 foodstuffs) were studied in five Upazillas namely as, Sonagazi, Dagan Bhuiya, Feni Sadar, Fulgazi and Parsuram of Feni district taking three samples of each kind from each upazilla. Samples of each kind together with the standard reference material (SRM) were irradiated in the same neutron flux and the gamma-rays of nuclides from the irradiated samples were assessed and screened for As, Br, U, Th, Cr, Sc, Fe, Zn and Co in soils and As, Br, Na, K, Cr, Sc, Fe, Zn and Co in vegetables (i.e; eddoe, taro, green papaya, plantain, potato, callaloo, bottle ground and carambola). The measurement of gamma-rays was carried out by means of a calibrated high resolution HPGe detector. The concentration of product nuclides containing in the irradiated samples was determined from the peak count-rates of prominent gamma-lines for the corresponding nuclides. Among all contaminants, only As, Zn and Cr for both samples were focused because of their higher values compared with the local as well as the world typical values. The present results revealed that the mean levels of As in Parsuram, Feni Sadar and Pulgazi upazillas are higher than the world typical value of 2 mg/kg. The mean values of Zn and Cr for all upazillas are higher than the world typical values 32 and 27.9 mg/kg, respectively. For the case of vegetables, the mean concentration of As is found only in Eddoe (5.33 ppm) and Taro (1.46 ppm) collected from Sonagazi and Feni Sadar upazilla; which are higher than the values in Samta (0.1 ppm for eddoe and 0.44 ppm for taro) under Jessore district of Bangladesh. The mean concentrations of Zn and Cr in all kinds of vegetables are higher compared with the existing local values as well as the world typical values. The mean estimated daily dietary intake of As, Zn and Cr from vegetables are found to be 0.105, 12.47 and 3.53 mg respectively, which are higher than the recommended values of some countries. The consumption of toxic metals in vegetables is a risk for public health in the studied area.

Measurement of neutron capture cross sections for 141Pr from 0.5 to 1.6 MeV

Cross sections of 141Pr ( n , γ ) 142Pr reaction are measured at neutron energies of 0.54, 1.09 and 1.59 MeV using the activation method. The activities of the products are counted with a high resolution HPGe detector γ -ray spectrometer. The neutron fluence is determined by 197Au ( n , γ ) 198Au reaction cross sections. The errors of the measured results are ± 6 – 7 % . The neutron capture cross sections for this reaction are also calculated with the NUNF code. Our results are compared with those of other authors. Recommendations for inclusion of data in the energy region 0.05 – 3.90 MeV are made, these being in good agreement with the ENDF/B-VI data.

Energy dispersive X-ray diffraction as a means to identify illicit materials: A preliminary optimisation study

Energy dispersive X-ray diffraction is proposed as a suitable non-destructive method to rapidly identify illicit drugs in parcels. A preliminary data set of 7 illicit drug samples and a possible cutting agent has been collected with a range of count times using a tungsten target X-ray source, a high resolution HpGe detector and a variable geometry diffraction cell. These results have been used to calibrate and train multivariate analysis software to predict the drug content in previously unseen spectra.

Study of the spatial distribution of natural radioactivity in the upper Egypt Nile River sediments

Sediment samples were collected along the Upper Egypt Nile River region starting from Aswan in the south to the north of El-Minia Governorate. Gamma radiation measurements were performed using high resolution HPGe detector with low background PC multichannel spectrometer. The gamma measurements of the alluvial sediments revealed the presence of the natural long-lived radioisotopes 238U, 232Th and 40K. The ranges of their activity concentrations were 3.83 ± 1.54 – 34.94 ± 4.01 , 2.88 ± 1.07 – 30.10 ± 1.83 and 112.31 ± 4.77 – 312.98 ± 12.24 Bq / kg , respectively. The measured activity concentrations differ widely as their presence in the Nile River depends on the pertinent environmental situation such as the presence of dams, barrages and sediments type. The other factors controlling the distribution of the detected natural radioisotopes have been discussed. Absorbed dose rates have been calculated for each location with range 12.71 ± 0.96 – 38.17 ± 1.55 nGy / h . Also, the estimated activity utilization indexes have been presented. The ratios between the detected radioisotopes have been calculated.

LOW-SPIN STATES OF 76Se EXCITED IN 76Br(β++EC)76Se DECAY

The decay of bromine-76 was studied using high resolution HpGe detectors in singles and coincidence mode. Bromine-76 was produced via two reactions: 75 As (α,3 n )76 Br and 76 Se ( p , n )76 Br . The results of these experiments verified the previously reported levels of 76 Se . In addition to the previously described transitions and levels, 37 new γ-rays and 15 new energy levels were found for the first time.

Properties of 152 Gd collective states

The decays of 152Tb (T 1/2 = 17.5 h) and 152Gd excited states have been investigated by the analysis of $\gamma$ -rays and $\gamma\gamma$ -coincidences measured with the use of high-resolution HPGe detectors. The source of 152Tb was prepared by chromatographic isolation followed by electromagnetic separation from a tantalum target irradiated by an internal proton beam of the LNP JINR phasotron. New and more precise data on the $\gamma$ -transitions and excited states of 152Gd are reported. Using previously published data on internal-conversion electrons many transition multipolarities are suggested, some of them with E0 admixture. The ${\rm EC}/\beta^ + $ ratio was found for a number of low-lying levels, for most of the levels their spins, parities, and $\log ft$ are given. The excited levels of 152Gd were deduced from the analysis of $\gamma\gamma$ -coincidences. The experimental level energies and reduced transition probabilities are compared with the calculations by phenomenological formulae as well as in the frameworks of theoretical models.

Cross sections for the formation of69Znm,gand71Znm,gin neutron induced reactions near their thresholds: Effect of reaction channel on the isomeric cross-section ratio

Excitation functions were measured for the reactions ${}^{72}\mathrm{Ge}(n,\ensuremath{\alpha})$${}^{69}{\mathrm{Zn}}^{m,g},$ ${}^{69}\mathrm{Ga}{(n,p)}^{69}{\mathrm{Zn}}^{m,g},$ ${}^{70}\mathrm{Zn}{(n,2n)}^{69}{\mathrm{Zn}}^{m,g},$ ${}^{74}\mathrm{Ge}(n,\ensuremath{\alpha}{)}^{71}{\mathrm{Zn}}^{m,g},$ and ${}^{71}\mathrm{Ga}{(n,p)}^{71}{\mathrm{Zn}}^{m,g}$ over the neutron energy range of 6.3--12.4 MeV. Quasimonoenergetic neutrons in this energy range were produced via the ${}^{2}\mathrm{H}{(d,n)}^{3}\mathrm{He}$ reaction using a deuterium gas target at the J\"ulich variable energy compact cyclotron. Use was made of the activation technique in combination with high-resolution HPGe-detector \ensuremath{\gamma}-ray spectroscopy. In a few cases low-level ${\ensuremath{\beta}}^{\ensuremath{-}}$counting was also applied. In order to decrease the interfering activities in those cases, either radiochemical separations were performed or isotopically enriched targets were used. For most of the reactions, the present measurements provide the first consistent sets of data near their thresholds. From the available experimental data, isomeric cross-section ratios were determined for the isomeric pair ${}^{69}{\mathrm{Zn}}^{m,g}$ in $(n,\ensuremath{\alpha}),$ $(n,p),$ and $(n,2n)$ reactions, and for the pair ${}^{71}{\mathrm{Zn}}^{m,g}$ in $(n,\ensuremath{\alpha})$ and $(n,p)$ reactions. Nuclear model calculations using the code STAPRE, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of both isomeric and ground states of the products. The calculational results on the total $(n,\ensuremath{\alpha}),$ $(n,p),$ and $(n,2n)$ cross sections agree fairly well with the experimental data. The experimental isomeric cross-section ratios, however, are reproduced only approximately by the calculation. For both the isomeric pairs investigated, the isomeric cross-section ratio in the $(n,p)$ reaction is higher than in other reactions.

Doppler-broadening of gamma rays following muon capture: search for scalar coupling

A precision measurement of the 277 keV γ ray produced by capturing muons in gaseous oxygen was performed using high-resolution HPGe detectors. The Doppler-broadened shape of this line is sensitive to the possible admixture into muon capture of genuine scalar interaction. This experiment complements, in the muon sector, in principle, similar ones undertaken recently in nuclear β decay. Using a procedure discussed in earlier papers, a fit to the experimental line-shape allowed us to obtain for the recoil–gamma correlation coefficient the value of a 1 2=0.096±0.041 (95% CL). The available evaluations of the contributing nuclear matrix elements, performed in the impulse approximation in the absence of scalar interaction, produce correlation coefficients in disagreement with our result. These evaluations are independent of the induced pseudoscalar coupling and so of the validity of the PCAC hypothesis, but their reliability and model dependence remain to be investigated.

Attenuation coefficients of soils and some building materials of Bangladesh in the energy range 276–1332 keV

The linear and mass attenuation coefficients of different types of soil, sand, building materials and heavy beach mineral samples from the Chittagong and Cox's Bazar area of Bangladesh were measured using a high-resolution HPGe detector and the γ-ray energies 276.1, 302.8, 356.0, 383.8, 661.6 and 1173.2 and 1332.5 keV emitted from point sources of 133Ba, 137Cs and 60Co, respectively. The linear attenuation coefficients show a linear relationship with the corresponding densities of the samples studied. The variations of the mass attenuation coefficient with γ-ray energy were exponential in nature. The measured mass attenuation coefficient values were compared with measurements made in other countries for similar kinds of materials. The values are in good agreement with each other in most cases.

The spin-neutrino correlation revisited in 28Si muon capture: a new determination of the induced pseudoscalar coupling gP/ gA

We describe an improved follow-up of our previous spin-neutrino correlation experiment, where the 1229 and 2171 keV gamma-rays emitted after the 28Si( μ, ν) 28Al(1 +, 2202 keV) reaction were observed by high-resolution HPGe detectors at different angles with respect to the muon spin. In the experiment described here, a magnetic field was used both to select events according to the spin-gamma angle and to measure the residual muon polarization by the muSR method. We further increase the precision of our result making use of new experimental and theoretical information. We obtain for the parameter x≡ M(2)/ M(−1) the value of x=0.239±0.029, which can be compared to our previous result (Brudanin et al., Nucl. Phys. A 587 (1995) 577) x=0.254±0.034 and to the value x=0.315±0.080 obtained recently at TRIUMF with a different technique. The coupling-constant ratio g P/ g A was deduced from the mean value x=0.247±0.027. Using renormalized transition operators calculated recently, we obtained for g P/ g A the solution range of −1.0 to +1.3 to be compared to the value of 7 predicted by PCAC for the free nucleon. This result confirms the strong quenching of g P/ g A reported earlier.

Identification of a New Isotope 186Hf

The new neutron-rich isotope 186Hf has been produced through a multinucleon transfer reaction by irradiation of natural tungsten targets with 60 MeV/u 18O projectiles. The 186Hf activities were separated radiochemically from the tungsten and reaction product mixture. The γ-ray singles spectra were measured with a high resolution HPGe detector. The new isotope 186Hf was identified based on the growth and decay of 737.5 keV γ rays from the β- decay of its daughter 186Ta. Its half-life has been determined to be 2.6 ± 1.2 min.

Primary gamma-rays from 53 keV neutron capture reaction in23Na

The nucleus23Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the24Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an exact energy calibration within 7 MeV,56Fe(n,γ)57Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the27Al(p,γ)28Si reaction atEp=2046 keV. The neutron binding energy of24Na was determined to be 6959.75 keV.

27Al(n,xγ)reactions for neutron energies from 3 to 400 MeV

The prompt \ensuremath{\gamma} radiation from the interaction of fast neutrons with aluminum was measured using the white neutron beam of the WNR facility at the Los Alamos National Laboratory. Aluminum samples were positioned at about 20 m or 41 m distance from the neutron production target. The spectra of the emitted \ensuremath{\gamma} rays were measured with a high-resolution HPGe detector. The incident neutron energy was determined by the time-of-flight method and the neutron fluence was measured with a ${}^{238}\mathrm{U}$ fission chamber. From the \ensuremath{\gamma}-ray spectra excitation functions for prominent \ensuremath{\gamma}-ray transitions in various residual nuclei (in the element range from F to Al) were derived for neutron energies from 3 to 400 MeV. Up to 200 MeV incident neutron energy the results are compared with the predictions of nuclear model calculations performed with the code GNASH. This code combines compound nucleus calculations using Hauser-Feshbach statistical theory with preequilibrium calculations from an exciton model including multiple preequilibrium processes. For the majority of the \ensuremath{\gamma}-ray transitions there is reasonable agreement between the measured and the calculated cross sections.

Gamma Decay of the Lowly Excited States of 229Ac

By bombarding the natural thorium targets with 14 MeV neutrons, 229Ra was produced through the reaction 232Th(n,α)229Ra. The radium activities were separated from the irradiated targets by coprecipitation with BaCl2. A total of 18 weak γ rays with energies of 14.5, 15.6, 18.8, 21.8, 22.5, 44.0, 47.5, 55.0, 63.0, 69.6, 93.6, 94.1, 98.5, 102.2, 104.5, 106.1, 161.1, and 171.5 keV, which could be assigned to the decay of 220Ra, has been observed in the isolated radium fractions employing high-resolution HPGe detectors and γ(x)-γ coincidence methods. A decay scheme of 229Ra based on these observations has been proposed.

The decay scheme of 229Ra

By bombarding the natural thorium targets with 14 MeV neutrons, 229Ra was produced through the reaction 232Th(n,α)229Ra. The radium activities were separated from the irradiated targets by coprecipitation with the BaCl2. A total of 18 new weak γ rays with energies of 14.5, 15.6, 18.8, 21.8, 22.5, 44.0, 47.5, 55.0, 63.0, 69.6, 93.6, 94.1, 98.5, 102.2, 104.5, 106.1, 161.1, and 171.5 keV which could be assigned to the decay of 229Ra were observed in the isolated radium fractions employing high resolution HPGe detectors and γ(χ)- γ coincidence methods. A decay scheme of 229Ra based on these observations is proposed.

Instrumental neutron activation analysis of lanthanides and other elements employing CIRUS reactor as a thermal neutron source

The high thermal neutron flux provided by the CIRUS reactor (1×1013 n cm−2s−1) has been used to determine elements having long half-lives or poor thermal neutron crosssections. Selective cooling time and the use of a high resolution HPGe detector in conjunction with a PC based MCA unit have made it possible to analyze many elements in a single irradiation run. The method developed has been used for the analysis of ores such as Ilmenite, Rutile, Sillimanite, Garnet, Zircon and Monazite.

Study of some nuclear parameters in the decay of 131Ba

The sum peak method has been applied to calculate K-electron capture probabilities to 216, 373, 585, 620 and 1048 keV levels of 131Cs. The relative and absolute intensities of γ-rays have been calculated using a high-resolution HPGe detector. K-conversion coefficients of 123 and 133 keV transitions have been calculated using summing phenomena.

The α-decay of 236Pu to 232U

The γ-spectrum following the α-decay of 236Pu was reinvestigated using a high resolution HPGe detector. The energy and intensity of 26 γ-transitions were measured accurately; 21 of these were observed for the first time. All γ-rays were placed in a 232U level scheme accounting for 13 levels of which 8 are reported for the first time. The ground state rotational band was found to be fed up to spin I π =8 + and the K π =0 − octupole band to be fed up to I=5.

TheK-capture probabilities in the decay of113Sn

A high-resolution HPGe detector was used to measure gamma-rays, X-rays and their sum coincidences in the electron capture decay of113Sn.K-capture probabilities (PK) to the (1/2)+→(3/2)− and the (1/2)+→(1/2)− first-forbidden non-unique transitions to the 646.7 keV and 391.0 keV levels of the daughter nucleus were reported as 0.867(27) and 0.869(16), respectively. TheQ-value is reported as (1021±10) keV. The dependence ofPK onQ-value is tested.

K-capture probabilities in the decay of75Se

A high-resolution HPGe detector was used to determine theK-capture probabilities in the decay of152Eu. ThePK values leading to 1529 keV, 1233 keV, 1085 keV levels in the daughter nucleus were determined by the sum peak method. ThePK value leading to the level at 1085 keV is determined for the first time.PL values for the three levels are deduced using the present experimentalPK values and theoreticalPL/PK ratios. The dependence ofPK values on theQ value is also tested.