High-resolution Gamma-ray Spectrometer Research Articles

Measurements and model calculations of isomeric cross section for (n,α) reaction on 140Ce isotope around 14 MeV neutrons

In this work, cross sections were measured for the 140Ce(n,α)137mBa (T1/2=2.552min) reaction at neutron energies from 13.57 to 14.83MeV. The neutrons were produced via the 3H(2H,n)4He reaction on a neutron generator using a solid Ti–T target. The activation technique was used, and induced gamma activities were measured by a high resolution gamma-ray spectrometer. Corrections were made for the effects of gamma-ray attenuation, random coincidence (pulse pileup), coincidence summing, dead time, neutron flux fluctuations, and low-energy neutrons. The measured cross sections were compared with statistical model (TALYS code) calculation results and the experimental data in the available literature.

Uranium-induced background of germanium gamma-ray spectrometers

The uranium-induced background in eight high-resolution gamma-ray spectrometers was analyzed in order to identify the locations of its sources. On the basis of the energy dependence of the peak count rates, normalized to units of emission probability and detection probability, the contributions of the molecular sieve and the beryllium window were extracted. Based on the uncertainties achieved the contribution of the detector shields could not be observed. However, some correlations between the construction of the detectors and the values of the parameters describing the energy dependence were observed and the uranium activity in the beryllium windows was assessed.

The worldwide NORM production and a fully automated gamma-ray spectrometer for their characterization

Materials containing radionuclides of natural origin, which is modified by human made processes and being subject to regulation because of their radioactivity are known as NORM. We present a brief review of the main categories of non-nuclear industries together with the levels of activity concentration in feed raw materials, products and waste, including mechanisms of radioisotope enrichments. The global management of NORM shows a high level of complexity, mainly due to different degrees of radioactivity enhancement and the huge amount of worldwide waste production. The future tendency of guidelines concerning environmental protection will require both a systematic monitoring based on the ever-increasing sampling and high performance of gamma ray spectroscopy. On the ground of these requirements a new low background fully automated high-resolution gamma-ray spectrometer MCA_Rad has been developed. The design of Pb and Cu shielding allowed to reach a background reduction of two order of magnitude with respect to laboratory radioactivity. A severe lowering of manpower cost is obtained through a fully automation system, which enables up to 24 samples to be measured without any human attendance. Two coupled HPGe detectors increase the detection efficiency, performing accurate measurements on sample volume (180 cc) with a reduction of sample transport cost of material. Details of the instrument calibration method are presented. MCA_Rad system can measure in less than one hour a typical NORM sample enriched in U and Th with some hundreds of Bq/kg, with an overall uncertainty less than 5%. Quality control of this method has been tested. Measurements of certified reference materials RGK-1, RGU-2 and RGTh-1 containing concentrations of K, U and Th comparable to NORM have been performed, resulting an overall relative discrepancy of 5% among central values within the reported uncertainty.

Cross section measurements for 141Pr(n,γ)142Pr reaction at neutron energies from 13.5 to 14.8 MeV

Activation cross-sections were measured for the 141Pr(n,γ)142Pr reaction at three different neutron energies from 13.5 to 14.8 MeV. The fast neutrons were produced via the 3H(d,n)4He reaction on Pd-300 neutron generator. The natural high-purity Pr2O3 powder was used as target material. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with high-purity germanium detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluences were determined by the cross section of 27Al(n,α)24Na reaction. The neutron energy in the measurement were by the cross section ratios of 90Zr(n,2n)89m+gZr and 93Nb(n,2n)92mNb reactions. The data for 141Pr(n,γ)142Pr reaction cross sections are reported to be 3.3 ± 0.2, 2.7 ± 0.2 and 2.2 ± 0.2 mb at 13.5 ± 0.2, 14.1 ± 0.2, and 14.8 ± 0.2 MeV incident neutron energies, respectively. Results were discussed and compared with some corresponding values found in the literature.

Influence of the thorium decay series on the background of high-resolution gamma-ray spectrometers

The background induced by the members of the thorium decay sequence in six high-resolution, gamma-ray spectrometers was analyzed. For the analysis, the count rates in the peaks of the background spectra, normalized to the unit of emission probability and detection probability, were used. The energy dependence of these normalized count rates carries information about the location of the sources of contamination. The contributions of the detector contamination, the contamination of the shielding material and the radiation penetrating the shield were calculated. The comparison of these contributions among the spectrometers pointed to the weaknesses of some shields, making such a comparison a useful tool for assessing the effectiveness of the shields.

Estimation of possible radiological hazards from natural radioactivity in commercially-utilized ornamental and countertops granite tiles

The aim of this study is to estimate natural radioactivity levels of commercially-utilized ornamental or countertops granite tiles collected from major retailers in Turkey and possible radiological hazards from usage of these materials by calculating external exposure and internal index, indoor absorbed gamma dose rate and the corresponding annual effective dose. The activity concentrations of 226Ra, 232Th and 40K were determined for 42 kinds of different granite tiles using high-resolution gamma-ray spectrometer. The activity concentration of 226Ra, 232Th and 40K varied from 9.2 to 192.5Bqkg−1 (with a mean of 88.4±6.9Bqkg−1), 7.5 to 344.6Bqkg−1 (with a mean of 95.3±10.0Bqkg−1) and 92.1 to 4155.9Bqkg−1 (with a mean of 1055.2±103.0Bqkg−1), respectively. The estimated radiological hazard indices were revised in the 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 superficial materials. The indoor absorbed gamma dose rates estimated from the activity concentrations of 226Ra, 232Th and 40K and the corresponding annual effective doses varied from 4.74 to 85.27nGyh−1 and 0.02 to 0.42mSv, respectively.

Cross-sections for formation of 99mTc through natRu(n,x) 99mTc reaction induced by neutrons at 13.5 and 14.8 MeV

The cross-sections for formation of metastable state of 99Tc (99mTc, 140.511keV, 6.01h) through natRu(n,x)99mTc reaction induced by 13.5MeV and 14.8MeV neutrons were measured. Fast neutrons were produced via the 3H(d,n)4He reaction on the K-400 neutron generator. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with a high-purity germanium (HpGe) detector. Measurements were corrected for gamma-ray attenuations, dead time and fluctuation of neutron flux. Data for natRu(n,x)99mTc reaction cross sections are reported to be 9.6±1.5 and 9.2±1.1mb at 13.5±0.2 and 14.8±0.2MeV incident neutron energies, respectively. Results were compared with the data by other anthors.

Measurements of activation cross sections for 175Lu(n, α) 172Tm, 176Lu(n, α) 173Tm and 175Lu(n, p) 175m+gYb reactions induced by neutrons around 14 MeV

The cross sections for the 175Lu(n, α) 172Tm, 176Lu(n, α) 173Tm and 175Lu(n, p) 175m+gYb reactions have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique. The first data for 175Lu(n, α) 172Tm reaction cross sections are presented. In our experiment, the fast neutrons were produced via the 3H(d, n) 4He reaction on K-400 Neutron Generator at Chinese Academy of Engineering Physics (CAEP). Induced gamma activities were measured by a high-resolution (1.69 keV at 1332 keV for 60Co) gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluences were determined by the cross section of 93Nb(n, 2n) 92mNb or 27Al(n, α) 24Na reactions. The neutron energy in the measurement was by the cross section ratios of 90Zr(n, 2n) 89m+gZr and 93Nb(n, 2n) 92mNb reactions. The results were discussed and compared with experimental data found in the literature and with results of published empirical formulae.

New estimates of the gamma-ray line emission of the Cygnus region from INTEGRAL/SPI observations

The Cygnus region harbours a huge complex of massive stars at a distance of 1.0-2.0kpc from us. About 170 O stars are distributed over several OB associations, among which the Cyg OB2 cluster is by far the largest with about 100-120 O stars. As a consequence of their successive nuclear-burning episodes, these massive stars inject large quantities of radioactive nuclei into the interstellar medium such as 26Al and 60Fe. The gamma-ray line signal from the latter is a solid tracer of ongoing nucleosynthesis. We want to compare the decay emission from the Cygnus region with predictions of recently improved stellar models. As a first step, we establish observational constraints upon the gamma-ray line emission from 26Al and 60Fe, with particular emphasis placed on separating the emission due to the Cygnus complex from the foreground and background mean Galactic contributions. We used the high-resolution gamma-ray spectrometer INTEGRAL/SPI to analyse the 26Al and 60Fe decay signal from the Cygnus region. The weak gamma-ray line emissions at 1809 and 1173/1332keV have been characterised in terms of photometry, spectrometry, and source morphology. The 1809keV emission from Cygnus is centred on the position of the Cyg OB2 cluster and has a typical size of 9 degrees or more. The total 1809keV flux from the Cygnus region is (6.0 +/- 1.0) x10e-5 ph/cm2/s, but the flux really attributable to the Cygnus complex reduces to (3.9 +/- 1.1) x10e-5 ph/cm2/s. The 1809keV line centroid is agrees with expectations considering the direction and distance of the Cygnus complex, and the line width is consistent with typical motions of the interstellar medium. No decay emission from 60Fe has been observed from the Cygnus region and an upper limit of 1.6 x10e-5 ph/cm2/s was derived.

Development of a Gamma-Ray Detector With Iridium Transition Edge Sensor Coupled to a Pb Absorber

We have recently started to develop a high-resolution gamma-ray spectrometer for material defect analysis. Our gamma-ray detector is a microcalorimeter consisting of an iridium/gold bilayer transition edge sensor (TES) thermometer and a bulk Pb absorber, which is directly coupled to a TES with Stycast 2850FT epoxy. This paper describes our TES based gamma-ray detector and the first experimental results for 662 keV and 1173 keV incident gamma-rays. We report an energy resolution of 4.7 keV at 662 keV and 2.9 keV at 1173 keV.

7Be to 210Pb concentration ratio in ground level air in Málaga (36.7°N, 4.5°W)

Concentration of 7Be and 210Pb in air was continuously monitored, using a high-volume air sampler and a high-resolution gamma-ray spectrometer, at the University of Málaga 36.7°N, 4.5°W from 2000 to 2006. The variation of the data with time was studied by time series analyses and seasonal patterns were identified. The average monthly concentrations of 7Be ground level air were in the range of 2.47–14.9 mBq/m 3 and exhibited maximum specific activities in spring and summer and one minimum in winter. The maximum concentrations for 210Pb were observed in summer, with the average concentrations in the range of 0.24 to 1.44 m Bq/m 3. Frequency distributions of 7Be, 210Pb and 7Be/ 210Pb ratio can be well represented by the log-normal distributions. The 7Be/ 210Pb ratios were in the range of 4.5 to 25.7 with spring maxima and late fall/winter minima. The concentration data of 7Be and 210Pb with meteorological variables were correlated to understand the monthly variation of these radionuclides in air.

Measurements of activation cross-sections for the 96Ru(n,d*) 95gTc reaction for neutrons with energies between 13.3 and 15.0 MeV

In this study, activation cross-sections were measured for the 9 6Ru(n,d*) 95gTc reaction at three different neutron energies from 13.5 to 14.8 MeV. The fast neutrons were produced via the 3H(d,n) 4He reaction on a K-400 neutron generator. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with a high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The data for 9 6Ru(n,d*) 95gTc reaction cross-sections are reported to be 196±18, 253±22 and 298±22 mb at 13.5±0.2, 14.1±0.1 and 14.8±0.2 MeV incident neutron energies, respectively. Results were compared with the previous works.

月惑星ローバー搭載のための高分解能 MeV ラインガンマ線検出器の開発

月惑星ローバー搭載のための高分解能 MeV ラインガンマ線検出器の開発

Photon spectrometry for the determination of the dose‐rate constant of low‐energy photon‐emitting brachytherapy sources

Accurate determination of dose-rate constant (lambda) for interstitial brachytherapy sources emitting low-energy photons (< 50 keV) has remained a challenge in radiation dosimetry because of the lack of a suitable absolute dosimeter for accurate measurement of the dose rates near these sources. Indeed, a consensus value of lambda taken as the arithmetic mean of the dose-rate constants determined by different research groups and dosimetry techniques has to be used at present for each source model in order to minimize the uncertainties associated with individual determinations of lambda. Because the dosimetric properties of a source are fundamentally determined by the characteristics of the photons emitted by the source, a new technique based on photon spectrometry was developed in this work for the determination of dose-rate constant. The photon spectrometry technique utilized a high-resolution gamma-ray spectrometer to measure source-specific photon characteristics emitted by the low-energy sources and determine their dose-rate constants based on the measured photon-energy spectra and known dose-deposition properties of mono-energetic photons in water. This technique eliminates many of the difficulties arising from detector size, the energy dependence of detector sensitivity, and the use of non-water-equivalent solid phantoms in absolute dose rate measurements. It also circumvents the uncertainties that might be associated with the source modeling in Monte Carlo simulation techniques. It was shown that the estimated overall uncertainty of the photon spectrometry technique was less than 4%, which is significantly smaller than the reported 8-10% uncertainty associated with the current thermo-luminescent dosimetry technique. In addition, the photon spectrometry technique was found to be stable and quick in lambda determination after initial setup and calibration. A dose-rate constant can be determined in less than two hours for each source. These features make it ideal to determine the dose-rate constant of each source model from a larger and more representative sample of actual sources and to use it as a quality assurance resource for periodic monitoring of the constancy of lambda for brachytherapy sources used in patient treatments.

High resolution γ-ray spectroscopy of flares on the east and west limbs of the Sun

A new generation of Ge-based high-resolution gamma-ray spectrometers has allowed accurate measurements to be made of the profiles, widths and energies of the gamma-ray lines emitted in the impulsive phases of solar flares. Here we present measurements in two flares of the energies of the de-excitation lines of 12C and 16O at 4.4 and 6.1 MeV respectively by the Ge spectrometer SPI on board INTEGRAL, from which Doppler shifts are derived and compared with those expected from the recoil of 12C and 16O nuclei which were excited by the impacts of flare-accelerated ions. An anomalous Doppler measurement (in terms of recoil theory) has been reported by the Ge spectrometer RHESSI in a flare near the east limb, and explained by a tilt of the magnetic field lines at the footpoint of a magnetic loop away from the vertical, and towards the observer. This might be interpreted to imply a significant difference between the Doppler shifts on the east and west limbs, if it is a general phenomenon. SPI observed both east and west limb flares and found no significant difference in Doppler shifts. We also measured the shapes and fluences of these lines, and their fluence ratio to the 2.2 MeV line from the capture of flare-generated neutrons. Analyses of both quantities using thick-target models parametrized by solar physical and geometric quantities suggest that the two flares studied here also have magnetic fields tilted towards the observer, though the significance of the measurements is not high.

The dynamic range of ultra-high-resolution cryogenic gamma-ray spectrometers

We are developing high-resolution cryogenic gamma-ray spectrometers for nuclear science and non-proliferation applications. The gamma-ray detectors are composed of a bulk superconducting Sn foil absorber attached to a multilayer Mo/Cu transition-edge sensor (TES). The energy resolution of a detector with a 1×1×0.25 mm 3 Sn absorber is 50–90 eV FWHM for γ-rays up to 100 keV, and it decreases for larger absorbers. Here, we present the detector performance for different absorber volumes, and discuss the trade-offs between energy resolution and dynamic range.

Factors influencing ambient concentrations of 210Pb and 7Be over the city of Edinburgh (55.9°N, 03.2°W)

Concentrations of 210Pb and 7Be in air were continuously monitored, using a high-volume air sampler and a high-resolution gamma-ray spectrometer, during the period of July 2002 to June 2003 at the University of Edinburgh 55.9°N, 03.2°W. The time series of both radio-isotopes show seasonality, dependence on air-mass origin, residence time and precipitation. Surface air concentrations of 210Pb and 7Be ranged from 0.01 to 0.74 mBq m −3 and 0.63–6.54 mBq m −3, respectively. The measurements indicate that the average concentrations of both 210Pb and 7Be in surface air were 0.21 ± 0.01 and 2.50 ± 0.04 mBq m −3, respectively; which agrees closely with the corresponding values reported for coastal air measurements in Europe.

Measurements of activation cross-sections for the 19F(n, α) 16N reaction for neutrons with energies between 13 and 15 MeV

In this study, activation cross-sections were measured for the 19F(n, α) 16N reaction at six different neutron energies from 13.5 and 14.9 MeV. The fast neutrons were produced via the 3H(d,n) 4He reaction on SAMES T-400 neutron generator. The cyclic activation technique was used. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with high-purity germanium (HpGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. Results were compared with the previous works.

Fabrication of Mo/Cu Multilayer and Bilayer Transition Edge Sensors

We are developing cryogenic high-resolution X-ray, Gamma-ray and neutron spectrometers based on superconducting Mo/Cu transition edge sensors. Here we discuss the sensor design for different applications, present the photolithographic fabrication techniques, and outline future detector development to increase the spectrometer sensitivity.

Natural radiation levels in powdered milk samples

The control and monitoring of radioactive elements in foodstuffs is fundamental for human health maintenance. This work presents procedures to measure radioactivity levels in powdered milk samples and also a brief discussion of radionuclide transference from the environment to mankind. The measurements were performed utilizing a high-resolution gamma-ray spectrometer using an HPGe detector. The results allowed the quantification of 40K, 137Cs and 208Tl radionuclides. For 40K the average activity was 482 ± 37 Bq/kg and for 137Cs and 208Tl the lower level of detection was, respectively, 3.7 ± 1.1 and 0.5 ± 0.2 (Bq/kg). The results obtained for the milk samples were compared to data found in the literature and to the limits established by the Brazilian National Commission of Nuclear Energy (CNEN) to assure its safety to human consuption.