Γ-ray Spectroscopy Research Articles

GRAPhEME: Performances, achievements (@EC-JRC/GELINA) and future (@GANIL/SPIRAL2/NFS)

GRAPhEME is a γ-spectrometer developed by CNRS/IPHC Strasbourg (France), in collaboration with EC-JRC Geel (Belgium) and IFIN-HH Bucharest (Romania). With its 6 High Purity Planar Germanium detectors and one fission chamber, GRAPhEME, installed at the EC-JRC GELINA facility, was optimized for measurements of accurate (n, xnγ) cross sections on actinides. The experimental methodology is based on the prompt γ-ray spectroscopy coupled to time-of-flight measurements. In this paper, we present an overview of fifteen years of experiments with GRAPhEME at EC-JRC GELINA facility, illustrated by main achievements to highlight the performances reached by our spectrometer. Beyond the experimental work, a close collaboration with theoreticians has emerged allowing the use of the data produced with GRAPhEME to test and constraint nuclear reaction codes like TALYS, CoH and EMPIRE. In a near future, GRAPhEME will be available to start measurement campaigns at the new neutron beam facility SPIRAL2/NFS. There, studies of (n, 2n) and (n, 3n) reactions will be possible and will complete the work done at EC-JRC GELINA on (n, n ) reactions. Despite the amount of cross section data provided by GRAPhEME up to now, the prompt γ-ray spectroscopy method presents some weaknesses that our collaboration tries to overcome. This goes through new calculation schemes based on theoretical modeling constrained on experimental data to infer the total (n, xn) cross section, new instrument to measure conversion electrons but also by being proactive in dissemination activities to make the nuclear structure community aware of our needs about new accurate nuclear structure information on actinides.

Gamma-Ray Spectrum Measurement from Capture Reactions of Uranium-238 for Thermal and Resonance Energy Neutrons

γ-ray spectrum from the capture reaction of 238U is measured for the thermal and resonance energy neutrons at KURNS-LINAC facility. Prominent primary γ ray of 3.297 MeV listed in CapGam is not observed for the thermal energy neutrons. The measured γ-ray spectrum is varied with neutron energy so that we can expect neutron spectrum inducing 238U(n,γ) reactions in critical / subcritical cores could be deduced by the γ-ray spectroscopy for the cores. Preliminary deduced ratio of 4.060 MeV γ-ray emission to capture for the thermal energy neutron agrees with CapGam so that the deduction scheme is considered adequate.

Measurement of partial (n, n’γ) reaction cross-sections on highly radioactive nuclei of interest for energy production

In the context of the development of Gen. IV nuclear reactors, the GIF (Generation IV. International Forum) has selected six innovative technologies. Among them, one can highlight the concept of breeding for 232Th/233U and 238U/239Pu fuel cycles. But those nuclei, crucial for such cycles, suffer from a lack of precise knowledge (nuclear structure, reaction cross sections). In particular, it has been demonstrated that neutron inelastic scattering reaction cross sections are not known with sufficient precision for the isotopes 238U and 239Pu, and not known at all experimentally for 233U. In order to perform simulations of innovative reactor cores for the development of those technologies, the knowledge of the reaction cross section has to be improved which implies that new measurements have to be done. The GRAPhEME (GeRmanium array for Actinides PrEcise MEasurements) experimental setup, developed by the IPHC laboratory from CNRS and installed at the EC-JRC-Geel GELINA facility is a powerful tool to answer this need [1, 2]. Combining the prompt γ-ray spectroscopy and the time-of-flight methods, it measures partial (n, xnγ) reaction cross sections. This paper reports on the improvements made on the GRAPhEME setup and data analysis methodology to tackle the challenge of (n, xnγ) cross section measurements on high activity actinides. Results obtained so far on 233U are presented compared to TALYS calculations.

New collective structures in Au179 and their implications for the triaxial deformation of the Pt178 core

The extremely neutron-deficient isotope Au179 has been studied by a combination of in-beam γ-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/2−, T1/2=328 ns isomer. A new rotational band, associated with the unfavored signature band of the 1h9/2⊕2f7/2 proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and T1/2=2.16(8)µs was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the 1i13/2 proton-intruder configuration. Calculations based on the particle-plus-triaxial-rotor model were performed to interpret the data. On the basis of these calculations, the new 1h9/2⊕2f7/2 rotational band is interpreted as due to triaxial deformation of the underlying configuration with β2≈0.26 and γ≈27∘. Observed non-yrast states of the positive-parity 1i13/2 intruder configuration are interpreted as due to triaxial deformation with β2≈0.26 and γ≈20∘.5 MoreReceived 9 May 2022Accepted 21 November 2022DOI:https://doi.org/10.1103/PhysRevC.106.064324©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective levelsIsomer decaysLifetimes & widthsNuclear structure & decaysProperties150 ≤ A ≤ 189Nuclear Physics

Measurement of neutron capture cross sections for the 174Yb(n,γ)175Yb reaction at thermal and epithermal energies

Herein, we measured the thermal neutron capture cross section (σ0) and resonance integral (I0) of the 174Yb(n,γ)175Yb reaction relative to those of the reference reaction 197Au(n,γ)198Au. Measurements were conducted based on the activation method using pulsed neutrons combined with the Cd ratio method and offline γ-ray spectrometry. Pulsed neutrons were generated on a 100 MeV electron linac of the Pohang Accelerator Laboratory, Korea. Yb samples and Au monitors were irradiated with and without a 0.5 mm Cd cover to absorb thermal neutrons. The neutron flux was determined via the 115In(n,γ)116mIn reaction. The induced activities of the reaction products were measured using a gamma spectrometer based on a well-calibrated HPGe detector. For the 174Yb(n,γ)175Yb reaction, the thermal neutron capture cross section and resonance integral cross-section were obtained as σ0,Yb = 70.5 ± 4.2 b and I0,Yb = 54.1 ± 4.2 b, relative to the corresponding values of σ0,Au = 98.65 ± 0.09 b and I0,Au = 1550 ± 28 b for the 197Au(n,γ)198Au reference reaction. The obtained results were compared with the measured and evaluated data.

Excitation functions of alpha particle induced nuclear reactions on natBa up to 60 MeV

The excitation functions of nuclear reactions natBa(α,xn)132, 133m, 134, 135, 137m,g, 139, 141Ce, natBa(α,x)135, 140La and natBa(α,x)131, 133m, 135mBa were measured for the first time in the energy range of 60 → 20 MeV using stack foil technique combined with γ-ray spectrometry. A comparative analysis of the experimental results with TENDL-2021 data was carried out. The thick target yields of radioisotopes Ba, La, and Ce were calculated by integrating the values of the cross sections. The feasibility of practical use of the studied reactions for the production of medical radioisotopes 134Ce and 135La is discussed.

New cross-section measurements for the (n, 2n), (n, p), and (n, α) reactions on bromine in the 14 MeV region with detailed uncertainty quantification* *Supported by the National Natural Science Foundation of China (12165006, 11875016).

Measurement of the cross-sections of the 79Br(n, 2n)78Br, 81Br(n, p)81mSe, 81Br(n, α)78As, and 79Br(n, α)76As reactions was performed at specific neutron energies, precisely, 13.5±0.2, 14.1±0.2, 14.4±0.2, and 14.8±0.2 MeV, relative to the standard 93Nb(n, 2n)92mNb and 27Al(n, α)24Na reference reactions using offline γ-ray spectrometry and neutron activation. Monoenergetic neutrons were generated at the China Academy of Engineering Physics via a 3H(d, n)4He reaction using the K-400 Neutron Generator equipped with a solid 3H-Ti based target. The activity of the reaction produce was obtained using a high-purity germanium detector. The cross-sections of the (n, 2n), (n, p), and (n, α) reactions on the bromine isotopes were measured in the 13–15 MeV neutron energy range. The covariance analysis approach was employed for a thorough inspection of any uncertainties within the measured cross-section data. A discussion and comparison of the observed outcome were carried out with previously published data, especially with the results of the JENDL-4.0, JEFF-3.3, TENDL-2019, and ENDF/B-VIII.0 data libraries, along with the theoretical excitation function curve derived by employing the TALYS-1.95 program. Improved cross-section restrictions for the investigated processes in the 13–15 MeV neutron energy range will be obtained using the current findings, which will help to raise the caliber of associated databases. Furthermore, the parameters of relevant nuclear reaction models can be verified using this data.

Cross sections and calculated yields of some radionuclides of yttrium, strontium and rubidium formed in proton-induced reactions on enriched strontium-86: possibility of production of 85gSr, 83Rb and 82mRb in no-carrier-added form

Abstract Cross sections of the 86Sr(p,3n)84mY, 86Sr(p,αn)82mRb, and 86Sr(p,x)85gSr reactions were measured from their respective thresholds up to 16.2 MeV and from 23.0 to 44.1 MeV at FZJ, and from 14.3 to 24.5 MeV at LBNL, using 96.4% enriched 86SrCO3 as target material. Thin targets prepared by sedimentation were irradiated with protons in a stacked-form, and the induced radioactivity was measured by high-resolution γ-ray spectrometry. Nuclear model calculations based on the code TALYS reproduced our experimental cross section data well. From the excitation functions, the integral yields of the above three radionuclides were calculated. The yield of 85gSr via the natSr(n,γ) process was also measured using the TRIGA Mark-II reactor at AERE, Savar. A comparison of the reactor and cyclotron production of carrier-added 85gSr is given. The production possibilities of the three investigated radionuclides in no-carrier-added forms at a 30 MeV cyclotron via new routes are discussed.

Cross-sections of the 238U (n, γ) 239U reaction in the 3.0–7.0 MeV energy region measured by relative activation method* *Supported by the Key Laboratory of Nuclear Data foundation (6142A08200104)

The reaction cross-sections of 238U (n, γ)239U have been experimentally determined at neutron energies of 6.117 ± 0.119 MeV, 4.626 ± 0.086 MeV, and 3.622 ± 0.348 MeV employing the relative activation approach along with the off-line γ-ray spectroscopy method. The D (d, n)3He reaction was utilized to obtain monoenergetic neutrons of the required energy, and the 197Au (n, γ)198Au reaction cross-sections were adopted as the referential standard to ascertain the neutron capture cross-sections of 238U. Furthermore, the effects of low-energy scattered neutrons, neutron fluence fluctuations, counting of geometric corrections when measuring γ-rays, and neutron and γ-ray self-absorption caused by the sample thickness have been considered and revised in the present work. For a comparison with experimental results, the cross-sections of the 238U (n, γ)239U reaction were calculated theoretically with the original parametric TALYS-1.9 program. The experimental measurements were in contrast to previous experimental results and the evaluation data available for ROSFOND-2010, CENDL-3.2 and ENDF/B-VIII.0.

Measurement of the integrated cross section of 110Pd(γ,n)109mPd, 110Pd(γ,n)109gPd, and 110Pd(γ,x)108mRh reactions with 70 MeV bremsstrahlung

We measured the integrated cross sections of 110Pd(γ,n)109mPd, 110Pd(γ,n)109gPd and 110Pd(γ,x)108mRh reactions in the energy range from the reaction threshold to 70 MeV bremsstrahlung end-point energy. Measurements were performed by means of the activation method in combination with off-line γ-ray spectrometry. The induced activity of radionuclides was measured with a high-purity germanium (HPGe) detector and necessary corrections for γ-ray interferences were made. The integrated cross section of the studied reactions was measured relative to that of the monitor reaction 27Al(γ,2pn)24Na. Current results are compared with theoretical predictions using the TALYS-1.9 statistical nuclear model code. Calculations were performed using six different level density models in combination with eight γ-strength functions to determine which combinations best fit the experimental results. The present results are measured for the first time.

Towards in vivo applications of 111Ag perturbed angular correlation of γ-rays (PAC) spectroscopy

111Ag-perturbed angular correlation of γ-rays (PAC) spectroscopy provides information on the nuclear quadrupole interactions, and thereby on the local structure and dynamics of the silver ion binding site. Brownian rotational motion, i.e. rotational diffusion, of 111Ag-labeled molecules will significantly affect the PAC spectra. Here we illustrate this effect, by simulating 111Ag PAC spectra for 111Ag-labeled molecules with molecular masses spanning from 102 to 106 g/mol, reflecting a span from fast (small molecules) to slow (large molecules) rotational diffusion on the PAC time scale. The simulated spectra are compared to 111Ag-PAC data obtained from a pilot study involving 111Ag(I) bound to a designed chelator exhibiting fast reorientation in solution, as well as to 111Ag-labeled species formed by 111Ag(I) in human serum, exhibiting slow (or no) reorientation on the PAC time scale. The simulated and experimental data illustrate typical PAC signals that are likely to be observed in vivo, when following the fate of 111Ag-labeled compounds. Potential in vivo applications are stability studies of 111Ag-radiopharmaceuticals, dissociation studies of 111Ag from the labeled molecule followed by binding to another (bio)molecule, or binding of 111Ag-labeled probes to larger carriers such as proteins.

Yield Ratios of Isomeric Pairs \(^{196m,g}\)Au, \(^{186m,g}\)Ir, and \(^{183m,g}\)Os in the \(^{197}\)Au\((\gamma,xnyp)\) Reactions with 2.5 GeV Bremsstrahlung

The yield ratios of high to low spin states of the 196m,gAu, 186m,gIr, and 183m,gOs isomeric pairs produced by 197Au(γ,xnyp) reactions with a bremsstrahlung end-point energy of 2.5 GeV have been measured. Measurements were performed by the activation method in combination with off-line γ-ray spectrometry. The induced activity of the studied radionuclides was derived from the photo-peak area of the selected γ-ray after making the necessary corrections. The isomeric yield ratios obtained in this work are the first measurement. The relationships between the yield ratios of studied isomeric pairs with the value of high spin states, the spin difference between the high spin states and the target nucleus, and the number of nucleons emitted from the target nucleus are discussed.

Activation cross sections of alpha-particle-induced reactions on natural lanthanum up to 50 MeV

We performed experiments to measure the activation cross sections of α-particle-induced reactions on natLa up to 50 MeV. The production cross sections of the medical radionuclide 142gPr and simultaneously formed 139,138mPr, and 141,139gCe were obtained. The stacked-foil activation method and the high-resolution γ-ray spectrometry were employed for the measurements. The results were compared with previous experimental data and theoretical values deduced by TALYS (TENDL library). The production cross section data for 139gCe and 138mPr were determined for the first time.

An astronomical age-depth model and reconstruction of moisture availability in the sediments of Lake Chalco, central Mexico, using borehole logging data

Understanding the moisture history of low latitudes from the most recent glacial period of the latest Pleistocene to post-glacial warmth in continental tropical regions is hampered by the lack of continuous time series. We conducted downhole spectral gamma (γ) ray and magnetic susceptibility logs over 300 m of lacustrine deposits of Lake Chalco (Mexico City) to reconstruct an age-depth model using an astronomical and correlative approach, and to reconstruct long-term moisture availability. Our results suggest that the Lake Chalco sediments contain several rhythmic alternations with a quasi-cyclic pattern comparable to the Pleistocene benthic stack. This allows us to calculate a time span of about 500,000 years for this sediment deposition. We developed proxies for moisture, detrital input, and salinity, all based on the physical properties of γ-ray spectroscopy and magnetic susceptibility. Our results indicate that Lake Chalco formed during Marine Isotope Stage 13 (MIS13) and the lake level gradually increased over time until the interglacial MIS9. Moisture content is generally higher during interglacials than during glacials. However, two periods, namely MIS6 and MIS4, have higher moisture contents. We developed a model by comparing the obtained moisture proxy with climatic drivers, to understand how different climate systems drove effective moisture availability in the Chalco sub-basin over the past 500,000 years. Carbon dioxide, eccentricity, and precession are all key drivers of the moisture content of Lake Chalco over the past 500,000 years.

Performance tests of the B-RAD radiation survey meter

This article discusses performance tests of the B-RAD by ELSE NUCLEAR. The B-RAD is a portable survey meter for γ-ray spectrometry and γ-ray dose rate measurements able to operate in the presence of a strong magnetic field. The detector uses a 15 mm right cylinder LaBr 3 crystal coupled with a 16-pixel Silicon Photomultiplier array. The crystal, the photodetector and the front-end electronics (the probe) are enclosed in a case connected with a cable to a control unit. The latter includes the main electronics, a customised battery pack, two displays and a Faraday cage.More in detail, this paper investigates the instrument performance inside magnetic field, including linearity of its response and its angular response. An operational test is also reported to demonstrate a practical application. The performed tests show that the B-RAD can operate inside magnetic fields up to 2.5 T. Two small shortcomings were observed: a pulling force is felt especially on the control unit, which becomes rather intense for values of the magnetic fields above 1 T, and a slight reduction of the signal gain with increasing magnetic field intensity when the control unit is inside the field. The latter causes a variation of the measured dose rate of less than 10% at 1.5 T. The response of the B-RAD with dose rate is linear up to 20 mSv/h with discrepancies between the reference and the measured dose rate within 10%. The response is isotropic from −120° to ＋120°; beyond this limit the measured dose rate drops by 66% probably because of the scattering of the source photons with the case and some shielding effects.

Radium radioactivity in soil profiles following long term irrigation with high radioactivity fossil groundwater

High radioactivity in a relatively saline confined aquifer water in different locations of the Disi area (South East of Jordan) was reported by some authors who recommended further investigation on the impact of that water on irrigated soils. Five well water samples (jointly used for irrigation and drinking) and 28 surface and subsurface soil samples from five profiles were collected from that area for the purpose of this study. Selected mineralogical, chemical, and physical properties of the soil samples were determined. Mineralogical compositions of the 28 soil samples were identified using x-ray diffraction, x-ray fluorescence, and ICP-MS techniques. Determination of activity concentrations of 238U, 226Ra and 228Ra in the five well waters and 22 soil samples from 4 sites (including a native soil) were determined using γ-ray spectroscopy. The results showed low salinity levels of both soil and water samples and low clay and organic matter contents in all soil samples. Kaolinite and mica were the dominant clay minerals with Fe substituting Al in the octahedral layer of these minerals. The average activity concentration of 226Ra and 228Ra in the well-water samples were 0.31 ± 0.09 and 1.74 ± 0.12 BqL−1, respectively. Such a high specific activity could be ascribed to the water enrichment with 228Ra diffusing from 232Th-rich sandstone geologic strata. Average concentrations of 238U and 232Th in the soil samples (0–120 cm depth) were 1.48 ± 0.38 mg kg−1 and 4.78 ± 1.55 mg kg−1, respectively. High correlation between these two radionuclides (R2 = 0.90) indicated no specific enhancement of these two metals from external sources, especially through chemical precipitation from irrigation water. Average activity concentration of 238U, 226Ra, and 228Ra in the soil samples were substantially low (20.8 ± 5.6, 16.94 ± 4.48, and 20.7 ± 6.2 Bq kg−1, respectively). No particular changes were observed when comparing concentration or radioactivity of these radionuclides with depth of a given soil or between irrigated and native soil samples at comparable depths. This could lead to the conclusion that there was no appreciable precipitation or adsorption of these radioactive metals from the percolating irrigation water onto the sandy soil complex.

Reassigning the shapes of the 0+ states in the 186Pb nucleus

Across the physics disciplines, the 186Pb nucleus is the only known system, where the two first excited states, together with the ground state, form a triplet of zero-spin states assigned with prolate, oblate and spherical shapes. Here we report on a precision measurement where the properties of collective transitions in 186Pb were determined in a simultaneous in-beam γ-ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the {0}_{2}^{+} state and the interband {2}_{2}^{+}to {2}_{1}^{+} transition have been observed. We also present direct measurement of the energies of the electric monopole transitions from the excited 0+ states to the 0+ ground state. In contrast to the earlier understanding, the obtained reduced transition probability B(E2;{2}_{1}^{+}to {0}_{2}^{+}) value of 190(80) W.u., the transitional quadrupole moment | {Q}_{t}({2}_{1}^{+}to {0}_{2}^{+})| =7.7(33) eb and intensity balance arguments provide evidence to reassign the {0}_{2}^{+} and {0}_{3}^{+} states with predominantly prolate and oblate shape, respectively. Our work demonstrates a step-up in experimental sensitivity and paves the way for systematic studies of electric monopole transitions in this region. These electric monopole transitions probe the nuclear volume in a unique manner and provide unexploited input for development of the next-generation energy density functional models.

Ultrasensitive Radionuclide Analysis in Water and Sediments for Environmental Radiological Assessment near the Decommissioning Garigliano Nuclear Power Plant (Italy)

We report a high sensitivity study of actinides content in water and sediment matrices performed for the first time along the Garigliano river, near the nuclear power plant currently undergoing decommissioning, and in the marine environment surrounding the river mouth up to a depth of 100 m. Ultrasensitive accelerator mass spectrometry measurements were carried out to estimate the absolute values of 236U, 238U, 239Pu, and 240Pu concentrations and 236U/238U, and 239Pu/240Pu ratios. The accuracy of the measurements and the spatial distribution of the radionuclides enable us to discriminate the anthropogenic from the natural radionuclide’s contribution to the environmental radioactivity. The results indicate that the contribution to the anthropogenic contamination of past power plant operations is, in most of the examined environmental compartments, negligible compared to fallout. High resolution γ-ray spectrometry measurements for 137Cs and 40K show interesting correlations with the actinides results.

The upgraded low-background germanium counting facility Gator for high-sensitivity γ-ray spectrometry

We describe the upgrade and performance of the high-purity germanium counting facility Gator, which is dedicated to low-background γ-ray spectrometry. Gator is operated at the Gran Sasso Underground Laboratory in Italy, at an average depth of 3600 meter water equivalent, and employed for material screening and selection in ultra-low background, rare-event search experiments in astroparticle physics. The detector is equipped with a passive shield made of layers of copper, lead and polyethylene, and the sample cavity is purged with gaseous nitrogen maintained at positive pressure for radon suppression. After upgrading its enclosure, the background rate is (82.0 ± 0.7) counts/(kg·day) in the energy region 100 keV to 2700 keV, a 20% reduction compared to the previously reported rate. We show the stability of various operation parameters as a function of time. We also summarize the sample analysis procedure, and demonstrate Gator's sensitivity by examining one material sample, a candidate photosensor for the DARWIN experiment.

Calibration of an airborne γ-ray spectrometer based on an unmanned aerial vehicle using a point source

Due to the lack of physical calibration models of artificial radionuclides for airborne γ-ray spectrometers, it is difficult to accurately deduce the content of artificial radionuclides on the ground based on airborne γ-ray spectrometry. According to the airborne radiation monitoring standard of the International Atomic Energy Agency (IAEA) and domestic and foreign industry experience, a calibration method for an airborne γ-ray spectrum survey system (AGS) based on an unmanned aerial vehicle (UAV) using point source is proposed in this paper. After calibrating the system with general methods and obtaining satisfactory test results, four artificial radioactive point sources were selected to calibrate the developed AGS and then obtain the calibration parameters for these point sources. Based on the calibration parameters of these four radionuclides, the calibration parameters of other artificial radionuclides can be estimated to realize the function of quantitative measurement of artificial radioactive sources by the AGS based on UAVs.