Γ-ray Intensities Research Articles

Recommended Nuclear Structure and Decay Data for A=202 Isobars

Evaluated nuclear structure and decay data for all nuclei with mass number A=202 (202Os, 202Ir, 202Pt, 202Au, 202Hg, 202Tl, 202Pb, 202Bi, 202Po, 202At, 202Rn, 202Fr and 202Ra), are presented. All available experimental data are compiled and evaluated, and best values for level and γ-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, as well as other nuclear properties, are recommended. Inconsistencies and discrepancies that exist in the literature are discussed. A number of computer codes (https://www-nds.iaea.org/public/ensdf_pgm/) developed by members of the NSDD network were used during the evaluation process. This work supersedes the earlier evaluation by F.G. Kondev (2007Ko42), published in Nuclear Data Sheets108, 1471 (2007).

Excitation functions for [formula omitted]Ag(α,x) reactions with detailed covariance analysis

Natural silver targets were irradiated using an alpha particle beam to measure the activation cross sections of radioisotopes within the energy range of 23–40 MeV. The newly obtained cross section data, compared with previous experimental results, underline the importance of this work in the context of nuclear reactions and medical applications. Alpha particle induced reaction with natAg involved the production of radioisotopes such as 111In, 105Ag, 106mAg. In this study, we focused on calculating correlation matrices for the natAg(α,x) nuclear reactions. These matrices were generated by considering various interconnected variables, such as decay constants, particle number densities, γ-ray intensities and detector efficiencies for both monitor and sample nuclear reaction products.

Recommended Nuclear Structure and Decay Data for A = 200 Isobars

Evaluated nuclear structure and decay data for all nuclei with mass number A=200 (200Os, 200Ir, 200Pt, 200Au, 200Hg, 200Tl, 200Pb, 200Bi, 200Po, 200At, 200Rn, and 200Fr), are presented. All available experimental data are compiled and evaluated, and best values for level and γ-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, as well as other nuclear properties, are recommended. Inconsistencies and discrepancies that exist in the literature are discussed. A number of computer codes (https://www-nds.iaea.org/public/ensdf_pgm/) developed by members of the NSDD network were used during the evaluation process. This work supersedes the earlier evaluation by F.G. Kondev and S. Lalkovski (2007Ko42), published in Nuclear Data Sheets108, 1471 (2007).

Comparison between CLYC-6 and 3He for thermal neutron detection.

A Cs2LiYCl6:Ce crystal, enriched in 6Li to > 95% (CLYC-6), was investigated for thermal neutron detection: it was characterised in terms of intrinsic efficiency and γ-ray discrimination capability and compared with a 3He counter (partial 3He pressure 2.3atm). The intrinsic efficiency was determined by irradiating the detectors with thermal neutrons. The γ-ray discrimination capability was evaluated in a mixed neutron/137Cs field. The intrinsic efficiency per unit volume is about a factor of 6.45 larger for CLYC-6 than for the 3He counter. The detectors' performances in the presence of an intense γ-ray background are comparable: up to γ-ray fluence rates of the order of 105cm-2·s-1, both detectors correctly reject γ-rays. At fluence rates of the order of 106cm-2·s-1, CLYC-6 starts being affected by count losses due to γ-ray-induced dead time, while the 3He counter starts suffering from pile-up. Above this γ-ray intensity, both detectors are not reliable.

Determination of absolute Np L x-ray emission intensities from 241Am decay using a metallic magnetic calorimeter

Photon emission intensities of radionuclides, i.e. the number of emitted photons per decay, are the single most important decay data when the photon spectrometry technique is employed in ionizing radiation metrology. However, their precise measurement is problematic because they are usually determined by photon spectrometry with spectrometers having a detection efficiency calibrated with x-ray and γ-ray emission intensities from other radionuclides. Therefore, these intensities are ultimately interdependent and correlated to some extent. A novel method was applied to determine the photon intensities of α-emitting radionuclides by measuring the ratio between the rate of photons in the full energy peaks and the rate of detected α-particles with the same detection set-up. Thus, there is no need to calibrate the detection efficiency and to standardize calibration sources by primary methods. The main condition to reach low uncertainties is to have a spectrometer with an intrinsic detection efficiency close to unity for the measured photons and α-particles. This condition was fulfilled by a metallic magnetic calorimeter (MMC) with an intrinsic efficiency of around 99% between 5 keV and 25 keV. In addition, the MMC provides an ultra-high energy resolution of 28 eV (full width at half maximum), facilitating the processing of the spectrum. The method was applied to determine L x-ray emission intensities from the decay of 241Am(α) → 237Np emitted between 11.9 keV and 22.4 keV. A total L x-ray emission intensity of 37.90 (12) per 100 disintegrations was obtained; the value agrees well with previous measurements and has a lower uncertainty. The uncertainties of the L x-ray groups Lα, Lηβ and Lγ were improved by a factor of two. Moreover, due to the high-energy resolution of 28 eV, a detailed set of 33 L x-ray emission intensities are provided.

Nuclear Data Sheets for A=201

Evaluated nuclear structure and decay data for all nuclei with mass number A=201 (201Os, 201Ir, 201Pt, 201Au, 201Hg, 201Tl, 201Pb, 201Bi, 201Po, 201At, 201Rn, 201Fr, 201Ra) are presented. All available experimental data are compiled and evaluated, and best values for level and γ-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, as well as other nuclear properties, are recommended. Inconsistencies and discrepancies that exist in the literature are discussed. A number of computer codes (https://www-nds.iaea.org/public/ensdf_pgm/index.htm) developed by members of the NSDD network were used during the evaluation process. For example, the reported absolute γ-ray emission probabilities and their uncertainties in various decay data sets were determined using the GABS code. This work supersedes the earlier evaluation by F.G. Kondev (2007Ko06), published in Nuclear Data Sheets 108, 365 (2007).

The ASTRAL database for neutron-capture nucleosynthesis studies

Present nuclear reaction network computations for astrophysical simulations involve many different types of rates, including neutron-capture reactions of interest for the modeling of heavy-element nucleosynthesis. While for many of them we still have to rely on theoretical calculations, an increasing number of experimentally-determined cross sections have now become available. In this contribution, we present “ASTrophysical Rate and rAw data Library” (ASTRAL), a new online database for neutron-capture cross sections based on experimental results, mainly obtained through activation and timeof-flight measurements. For the evaluation process, cross sections were re-calculated starting from raw data and by considering recent changes in physical properties of the involved isotopes (e.g., half-life and γ-ray intensities). We show the current status of the database, the techniques adopted to derive the recommended Maxwellian-averaged cross sections, and future developments.

Gamma intensities for the [formula omitted]-decay of 97Zr

To determine the neutron flux in activation experiments, a commonly used monitor is zirconium and in particular the stable isotopes 94,96Zr. 96Zr is very sensitive to epithermal neutrons. Despite its widespread application, most gamma intensities of the radioactive neutron capture product, 97Zr, yield large uncertainties. With the help of a new γ spectroscopy setup and GEANT simulations, we succeeded in determining a new set of γ-ray intensities with significantly reduced uncertainties.

Thick-target yield of [formula omitted][formula omitted] ray from the resonant reaction [formula omitted]Li[formula omitted]Be at E[formula omitted] = [formula omitted

High energy γ-ray plays an important role in the study of the nuclear industry and nuclear physics. (p,γ) resonant reaction is a classic way to produce quasi-monochromatic γ-ray. The determination of (p,γ) yield is an important prerequisite for using this γ-ray source to carry out subsequent work. In this work, the 7Li(p,γ)8Be resonant reaction at Ep = 441 keV is utilized to produce 17.6 MeV γ-ray using the 2×1.7 MV tandem accelerator at CIAE. The full yield curve is measured for the first time. The maximum thick-target-yield of 17.6 MeV γ-ray is determined to be (3.2 ± 0.2)×10−9γ/p. This would lead to the γ-ray intensity of 2×108 /s when using 10 mA proton beam which has been typically available to date. This intensity is comparable to the one from the laser-Compton scattering facilities in operation. Thus can be used for study of photonuclear reactions.

Evidence for spherical-oblate shape coexistence in Tc87

Excited states in the neutron-deficient nucleus Tc87 have been studied via the fusion-evaporation reaction Fe54(Ar36,2n1p)Tc87 at 115 MeV beam energy. The AGATA γ-ray spectrometer coupled to the DIAMANT, NEDA, and Neutron Wall detector arrays for light-particle detection was used to measure the prompt coincidence of γ rays and light particles. Six transitions from the deexcitation of excited states belonging to a new band in Tc87 were identified by comparing γ-ray intensities in the spectra gated under different reaction channel selection conditions. The constructed level structure was compared with the shell model and total Routhian surface calculations. The results indicate that the new band structure in Tc87 is built on a spherical configuration, which is different from that assigned to the previously identified oblate yrast rotational band.1 MoreReceived 10 September 2021Revised 24 January 2022Accepted 23 March 2022DOI:https://doi.org/10.1103/PhysRevC.106.034304Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsLow & intermediate energy heavy-ion reactionsNuclear structure & decaysNucleon distributionTransfer reactionsProperties59 ≤ A ≤ 89Nuclear Physics

Detection of Diffuse γ-Ray Emission toward a Massive Star-forming Region Hosting Wolf–Rayet Stars

Isotopic and elemental abundances seen in Galactic cosmic rays (GCRs) imply that ∼20% of the cosmic-ray (CR) nuclei are probably synthesized by massive Wolf–Rayet (W-R) stars. Massive star clusters hosting W-R- and OB-type stars have been proposed as potential GCR accelerators for decades, in particular via diffusive shock acceleration at wind termination shocks. Here we report the analysis of Fermi Large Area Telescope data toward the direction of Masgomas-6a, a young massive star cluster candidate hosting two W-R stars. We detect an extended γ-ray source with a test statistic = 183 in the vicinity of Masgomas-6a, spatially coincident with two unassociated Fermi 4FGL sources. We also present the CO observational results of molecular clouds in this region, using the data from the Milky Way Imaging Scroll Painting project. The γ-ray emission intensity correlates well with the distribution of molecular gas at the distance of Masgomas-6a, indicating that these γ-rays may be produced by CRs accelerated by massive stars in Masgomas-6a. At the distance of 3.9 kpc of Masgomas-6a, the luminosity of the extended source is (1.81 ± 0.02) × 1035 erg s−1. With a kinetic luminosity of ∼1037 erg s−1 in the stellar winds, the W-R stars are capable of powering the γ-ray emission via neutral pion decay resulted from CR proton–proton interactions. The size of the GeV source and the energetic requirement suggests a CR diffusion coefficient smaller than that in the Galactic interstellar medium, indicating a strong suppression of CR diffusion in the molecular cloud.

Intense gamma-ray source based on focused electron beams from a laser wakefield accelerator

Laser wakefield accelerators generate ultrashort electron bunches with the capability to produce γ-rays. Here, we produce focused laser wakefield acceleration electron beams using three quadrupole magnets. Electron beams are then focused into a 3 mm lead converter to generate intense, focused bremsstrahlung γ beams. Experimental results demonstrate the generation and propagation of focused γ beams to a best focus spot size of 2.3 ± 0.1 × 2.7 ± 0.2 mm2 using a copper stack calorimeter. Monte Carlo simulations conducted using GEANT4 are in good agreement with experimental results and enable detailed examination of γ-ray generation. Simulations indicate that the focused γ beams contained 2.6 × 109 photons in the range of 100 keV to 33 MeV with an average energy of 6.4 MeV. A γ-ray intensity of 7 × 1010 W/cm2 was estimated from simulations. The generation of focused bremsstrahlung γ-ray sources can have important applications in medical imaging applications and laboratory astrophysics experiments.

Nuclear Data Sheets for A=203

Evaluated nuclear structure and decay data for all nuclei with mass number A=203 (203Os, 203Ir, 203Pt, 203Au, 203Hg, 203Tl, 203Pb, 203Bi, 203Po, 203At, 203Rn, 203Fr, 203Ra) are presented. All available experimental data are compiled and evaluated, and best values for level and γ-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, as well as other nuclear properties, are recommended. Inconsistencies and discrepancies that exist in the literature are discussed. A number of computer codes (https://www-nds.iaea.org/public/ensdf_pgm/index.htm) developed by members of the NSDD network were used during the evaluation process. For example, the reported absolute γ-ray emission probabilities and their uncertainties were determined using the GABS code. The γ-ray transition probabilities were determined using the RULER code and the corresponding uncertainties were estimated by means of a Monte-Carlo approach. This work supersedes the earlier evaluation by F.G. Kondev (2005Ko20), published in Nuclear Data Sheets 105, 1 (2005).

Structure of collective states built on the 11/2+ isomer in Os187 : Quasiparticle-plus-triaxial-rotor model and interpretation as tilted-precession bands

Background: The shape of most nuclei is described by its quadrupole deformation (showing the deviation from spherical shape) and its triaxiality (showing the deviation from axial symmetry). Nuclei affected by triaxiality show additional collective rotational bands, called γ bands, that appear at low excitation energy. The γ bands can be caused by the precession of a nucleus with triaxial shape, but can also arise from small γ vibrations around an axially symmetric shape. Purpose: The aim of this work is to search for new collective excitations in Os187 in particular related with the γ degree of freedom. Methods: The rotational structures of Os187 were populated by the W186(He4,3n)Os187 reaction at a beam energy of 37 MeV. The measurements of γ - γ coincidences, angular distribution ratios and γ-ray intensities were performed using eleven Compton-suppressed Ge clover detectors. Results: The previously known positive-parity band built on the 11/2+ isomer has been extended up and a new excited positive-parity band built above a 15/2+ state has been observed. The 11/2+ band was assigned a νi13/2 configuration while the new 15/2+ band was associated with a coupling of the valence i13/2 neutron with the γ band of the even-even core. The quasiparticle-plus-triaxial-rotor model calculations provide a good agreement with the experimental data for both bands. They describe the 15/2+ band as a collective excitation with respect to the 11/2+ band that corresponds to a precession of the intermediate nuclear axis similarly to the precession of a rotating top. Conclusions: As shown by the calculations, the new rotational band can be understood as resulting from the three-dimensional rotation of a triaxially-deformed nucleus. However, a description based on the vibrations of a γ-soft nuclear shape should also be investigated in order to firmly establish the nature of the excited positive-parity band. Further studies able to distinguish between these alternative descriptions will be beneficial.8 MoreReceived 11 May 2021Revised 10 June 2021Accepted 5 October 2021DOI:https://doi.org/10.1103/PhysRevC.104.044326©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective levelsElectromagnetic transitionsIsomer decaysNuclear structure & decaysNucleon distributionProperties150 ≤ A ≤ 189Nuclear Physics

New approach to precisely measure [formula omitted]-ray intensities for long-lived fission products, with results for the decay of 95Zr

For many fission products, the γ rays emitted following β decay provide an easily-detectable signature that can be used to identify their quantities and distributions in a sample. As a result, γ-ray spectroscopy is often exploited to study fission-product yields, provided sufficiently accurate information on the γ-ray intensity is available. However, in many cases, the uncertainties in the existing nuclear data are large enough that they compromise the precision achievable for modern experiments and applications. To address this need, we have developed a new experimental method that is well suited to precisely measure absolute γ-ray intensities in the β decay of long-lived fission products. The approach involves the production of a radiopure sample by implantation of a mass-separated ion beam from the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) facility on a thin carbon foil. The emitted β-decay radiation is detected with a 4π gas proportional counter and a meticulously efficiency-calibrated high-purity germanium (HPGe) detector. As a first measurement to demonstrate the approach, we studied the absolute γ-ray intensities of the strongest transitions following the β decay of 95Zr and its decay-daughter 95Nb, and determined them to fractional precisions of better than 1–2%. In addition, with a larger sample of activity produced through neutron irradiation of an isotopically-enriched Zr foil, we performed a high-precision measurement of the relative γ-ray intensities following the decay of 95Zr with just the HPGe detector. The sample-production method at CARIBU and the coincidence detection approach demonstrated here can be applied to study fission products with half-lives longer than a day, which includes isotopes important not only for nuclear-energy and national-security applications, but also for medical-isotope research and environmental monitoring.

Gamma-ray irradiation effects on CdTe solar cell dosimeter

Compact and radiation-tolerant radiation dosimeter without bias voltage application using solar cells such as CdTe was proposed for severe radiation environment near a nuclear reactor pressure vessel. In this work, γ-ray tolerance and γ-ray detection characteristics of CdTe solar cells were investigated. It was found that the CdTe solar cell has sufficient tolerance against γ-ray exposure up to 3 MGy. It was demonstrated that γ-ray induced current density linearly increased with increasing γ-ray intensity in the range up to approximately 1.5 kGy h−1. This result indicates that high dose-rate radiation detection can be performed using solar cells without voltage application. In addition, γ-ray sensitivity was successfully improved by a stack of CdTe solar cells with parallel connections. Furthermore, γ rays can be detected with high responsivity and small noise even under a high flux neutron environment.

Probing the nuclear structure of candidates for neutrinoless double-beta decay with fast neutrons

The low-lying, low-spin levels of several nuclei which are either the possible parent or daughter for neutrinoless double-beta decay have been studied with the (n,n’γ) reaction. From these measurements, level spins, level lifetimes, γ-ray intensities, and multipole mixing ratios were determined; however, considerable effort must be expended in elaborating the level schemes before comparisons of the level characteristics with large-scale shell model calculations are meaningful.

Performance Analysis of Natural γ-Ray Coal Seam Thickness Sensor and Its Application in Automatic Adjustment of Shearer’s Arms

The technology of coal-rock interface recognition is the core of realizing the automatic heightening technology of shearer’s rocker. Only by accurately and quickly identifying the interface of coal and rock can we realize the fully automatic control of shearer. As the only one used in the actual detection of coal mining machine drum cutting coal seam after the thickness of the remaining coal seam detection method, natural γ-ray has a very practical advantage. Based on the relationship between the attenuation of the natural γ-ray passing through the coal seam and the thickness of the coal seam, the mathematical model of the attenuation of the natural γ-ray penetrating coal seam is established. By comparing the attenuation intensity of γ-ray with or without brackets, it is verified that the hydraulic girders will absorb some natural γ-rays. Finally, this paper uses the ground simulation experiment and the field experiment to verify the correctness of the mathematical model and finally develop the natural γ-ray seam thickness sensor. The sensor has the function of indicating the thickness of the coal seam, measuring the natural γ-ray intensity, and storing and processing the data.

Spectroscopy of Cd99 and In101 from β decays of In99 and Sn101

We report on new γ-ray spectroscopy results from β decays of In99 and Sn101. 30 new γ rays were observed following the β decay of In99, and inconsistencies in the literature with respect to the γ rays following the β decay of Sn101 were addressed with two confirmed cases and two new transitions. The experimental γ-ray energies, intensities, and coincidence relationships are discussed with shell model calculations, where theoretical β-decay branching ratios from the parent nuclei and γ-ray cascades of excited states from the daughter nuclei were combined to generate hypothetical βγ spectra and βγγ coincidence matrices. The most intense β-delayed γ-ray branches in both Cd99 and In101 were well reproduced with this approach, and several γ rays were assigned to new excited states based on their good agreement with shell model predictions.

Study of charged particle activation analysis (II): Determination of boron concentration in human blood samples

Boron Neutron Capture Therapy (BNCT) is a radiotherapy for the treatment of intractable cancer. In BNCT precise determination of 10B concentration in whole blood sample before neutron irradiation of the patient, as well as accurate neutron dosimetry, is crucial for control of the neutron irradiation time. For this purpose ICP-AES and neutron induced prompt γ-ray analysis are generally used. In Ibaraki Neutron Medical Research Center (iNMRC), an intense proton beam will be accelerated up to 8 MeV, which can also be used for Charged Particle Activation Analysis (CPAA). Thus, in this study, we apply the CPAA utilizing the proton beam to non-destructive and accurate determination of 10B concentration in whole blood sample.A CPAA experiment is performed by utilizing an 8 MeV proton beam from the tandem accelerator of Nuclear Science Research Institute in Japan Atomic Energy Agency. The 478 keV γ-ray of 7Be produced by the 10B(p, α)7Be reaction is used to quantify the 10B in human blood. The 478 keV γ-ray intensity is normalized by the intensities of the 847 keV and 1238 keV γ-rays of 56Co originating from Fe in blood. The normalization methods were found to be linear in the range of 3.27 μg 10B/g to 322 μg 10B/g with correlation coefficients of better than 0.9999.