Cross Section Σ0 Research Articles

Integrated photonuclear cross sections in the giant dipole resonance of odd-mass actinide nuclei

This study explores the integrated total photonuclear cross section (σ0) within the context of the giant dipole resonance (GDR) in odd-mass actinide nuclei. Using artificial neural networks (ANNs) and adaptive neuro-fuzzy ınference system (ANFIS) machine learning algorithms, we analyze the GDR behaviors associated with the σ0 values in these nuclei. The modeling results obtained from ANFIS and ANN are compared among themselves and with the Translational Galilean Invariant Quasiparticle Phonon Nuclear Model (TGI-QPNM) and experimental data. Machine learning analysis and TGI-QPNM results provide valuable insights into the GDR characteristics of odd-mass actinides, shedding light on their photonuclear properties. The ANFIS model has achieved an R2 value of 0.98 and an RMSE of 0.19, while the ANN model (LM) has yielded an R2 value of 0.95 and an RMSE of 0.24. These findings deepen our understanding of nuclear physics, underscoring the role of artificial intelligence techniques in deciphering complex phenomena within nuclear structures. In conclusion, our study suggests that the ANFIS model, in agreement with TGI-QPNM results, generally outperforms the ANN (LM) method and could be a more effective tool for estimating the energy-weighted sum rule for GDR.

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.

Study and analysis of the optical absorption cross section and energy states broadenings in quantum dot lasers

In this report, we measured experimentally the modal absorption spectra of the InP and InAsP quantum dot (QD) lasers using multi-section device technique. The optical absorption cross section (σ0) and inhomogeneous broadening for the ground state (GS) and excited state (ES) were analyzed and calculated theoretically from the absorption spectra. The results showed that the InP QD laser exhibited σ0 to be 1.347×10−14 ​cm2.eV and 3.016×10−14 ​cm2eV for GS and ES respectively, whereas for the InAsP QD material it was found as 0.511×10−14cm2eV and 3.099×10−14cm2.eV for GS and ES respectively. Moreover, the inhomogeneous broadening in the GS increases from 35.6 eV to 63.6 eV when As was added to InP QD, similarly, the inhomogeneous broadening of ES increases from 46.9 eV to 103.8 eV. The alloying InP QDs with arsenic decreases the σ0 of the ground state (lasing state) and increases both inhomogeneous and linewidth broadenings. This finding may help the grower to control the growth conditions and the molecule fractions of the crystal to improve the spectral properties of the optoelectronics devices.

Thermal-neutron capture cross sections and resonance integrals of the 243Am(n,γ)244gAm and 243Am(n,γ)244m+gAm reactions

ABSTRACT The thermal-neutron capture cross sections (σ0) and resonance integrals (I0) were measured for the 243Am(n,γ)244gAm and 243Am(n,γ)244m+gAm reactions by a neutron activation method. Americium-243 samples were irradiated with a pneumatic tube and a hydraulic conveyer installed in the research reactor in Institute for Integral Radiation and Nuclear Science, Kyoto University. Alloy wires of Au/Al, Co/Al or Co foils were used as neutron monitors to measure thermal-neutron fluxes and epi-thermal Westcott’s indexes at irradiation positions. A 25-μm-thick gadolinium foil was used to separate reactions due to thermal- and epi-thermal neutron components, and a value of 0.133 eV was taken as a corresponding cut-off energy. Gamma-ray spectroscopy was applied to measure radioactivity of neutron monitors and the ground state of reaction products, while alpha-ray spectroscopy was applied to measure that of target 243Am and final reaction product 244Cm through the decay of 244m, 244gAm. By utilizing Westcott’s convention, the σ0 and I0 values were derived as 4.73 ± 0.27 barn and 96.5 ± 8.9 barn for the 243Am(n,γ)244gAm reaction, and 88.5 ± 4.0 barn and 2.30 ± 0.20 kilobarn for the 243Am(n,γ)244m+gAm reaction, respectively. The present result of σ0 for the production of 244m+gAm agreed with the reported value of 87.7 ± 5.4 barn measured with a time-of-flight method within the limits of uncertainties.

Measurement of the thermal neutron cross section and resonance integral of the 187Re(n,γ)188Re reaction

We measured the thermal neutron capture cross sections (σ0) and resonance integral (I0) of the 187Re(n,γ)188Re reaction relative to that of the 197Au(n,γ)198Au monitor reaction using neutron activation with the Cd ratio method. The investigated samples and monitors were irradiated with and without a 0.5-mm-thick Cd cover for the pulsed neutron source based on the 100-MeV electron linac at the Pohang Accelerator Laboratory (PAL). The induced activities for the reaction products were measured using a high-purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results, the necessary corrections were made. The thermal neutron capture cross sections and resonance integral of the 187Re(n,γ)188Re reaction were determined relative to reference values of σo,Au = 98.65 ± 0.09 barn and Io,Au = 1550 ± 28 barn from the 197Au(n,γ)198Au reaction, respectively. The corresponding values for the 187Re(n,γ)188Re reaction were determined to be σ0,Re = 75.6 ± 3.4 barn and I0,Re = 317 ± 22 barn, respectively. The obtained results are compared with the literature data and discussed.

Can GNSS Reflectometry Detect Precipitation Over Oceans?

AbstractFor the first time, a rain signature in Global Navigation Satellite System Reflectometry (GNSS‐R) observations is demonstrated. Based on the argument that the forward quasi‐specular scattering relies upon surface gravity waves with lengths larger than several wavelengths of the reflected signal, a commonly made conclusion is that the scatterometric GNSS‐R measurements are not sensitive to the surface small‐scale roughness generated by raindrops impinging on the ocean surface. On the contrary, this study presents an evidence that the bistatic radar cross section σ0 derived from TechDemoSat‐1 data is reduced due to rain at weak winds, lower than ≈ 6 m/s. The decrease is as large as ≈ 0.7 dB at the wind speed of 3 m/s due to a precipitation of 0–2 mm/hr. The simulations based on the recently published scattering theory provide a plausible explanation for this phenomenon which potentially enables the GNSS‐R technique to detect precipitation over oceans at low winds.

The electron trap parameter extraction-based investigation of the relationship between charge trapping and activation energy in IGZO TFTs under positive bias temperature stress

Experimental extraction of the electron trap parameters which are associated with charge trapping into gate insulators under the positive bias temperature stress (PBTS) is proposed and demonstrated for the first time in amorphous indium-gallium-zinc-oxide thin-film transistors. This was done by combining the PBTS/recovery time-evolution of the experimentally decomposed threshold voltage shift (ΔVT) and the technology computer-aided design (TCAD)-based charge trapping simulation. The extracted parameters were the trap density (NOT) = 2.6×1018 cm−3, the trap energy level (ΔET) = 0.6 eV, and the capture cross section (σ0) = 3 × 10−19 cm2.Furthermore, based on the established TCAD framework, the relationship between the electron trap parameters and the activation energy (Ea) is comprehensively investigated. It is found that Ea increases with an increase in σ0, whereas Ea is independent of NOT. In addition, as ΔET increases, Ea decreases in the electron trapping-dominant regime (low ΔET) and increases again in the Poole–Frenkel (PF) emission/hopping-dominant regime (high ΔET). Moreover, our results suggest that the cross-over ΔET point originates from the complicated temperature-dependent competition between the capture rate and the emission rate. The PBTS bias dependence of the relationship between Ea and ΔET suggests that the electric field dependence of the PF emission-based electron hopping is stronger than that of the thermionic field emission-based electron trapping.

Theoretical electronic structure of the cadmium monohalide molecules CdX (X = F, Cl, Br, I)

The potential energy and dipole moment curves for the lowest electronic states in the representation 2s+1Λ(±) of CdX (X = F, Cl, Br, I) molecules are investigated via complete active space self-consistent field (CASSCF) and multi-reference configuration interaction MRCI (single and double excitation with Davidson correction). For the bound states of CdX diatomic molecules the bond distances Re, the vibrational harmonic frequencies ωe, the rotational constants Be, the electronic energies relative to the ground state Te, and the permanent and transition dipole moments have been computed. The dissociation energy limits of the atomic levels of CdX compounds are also calculated. The transition dipole moment between the ground state X2Σ+ and (2)2Σ+ is investigated. Consequently, the transition dipole moment values of the upper state at its equilibrium position μ21, the emission angular frequency ω21, the Einstein coefficients of spontaneous and induced emissions (A21 and B21ω), the spontaneous radiative lifetime τspon, the emission cross section σ0, the line strength and the emission oscillator strength f21 are calculated along with the ionicity of the X2Σ+ and (2)2Σ+ states. The eigenvalues Ev, the rotational constants Bv, the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax of X2Σ+ states of the CdX diatomics are computed. The comparison of the results with those available in literature shows a very good agreement.

Neutron capture cross section measurements and theoretical calculation for the186W(n,γ)187W reaction

AbstractNeutron capture cross section (σ0) and resonance integral (I0) of the reaction186W(n,γ)187W were measured experimentally using the research reactor (ETRR-2) and an Am–Be neutron source, also calculated using TALYS-1.6 code. The present results ofσ0are (39.08±2.6, 38.75±0.98 and 38.33 barn) andI0are (418.5±74, 439.3±36 and 445.5 barn) by using the reactor, neutron source and TALYS-1.6, respectively. The present results are in acceptable agreement with most of the previous experimental and evaluated data as well as the theoretical calculations.

Threshold [formula omitted] photoproduction on transverse polarised protons at MAMI

Polarisation-dependent differential cross sections σT associated with the target asymmetry T have been measured for the reaction γp→→pπ0 with transverse target polarisation from π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σT have been used in combination with our previous measurements of the unpolarised cross section σ0 and the beam asymmetry Σ for a model-independent determination of S- and P-wave multipoles in the π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+ multipole.

Thermal neutron capture and resonance integral cross sections of 45Sc

The thermal neutron cross section (σ0) and resonance integral (I0) of the 45Sc(n,γ)46Sc reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (Gth) and resonance (Gepi) neutron self-shielding, the γ-ray attenuation (Fg) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the 45Sc(n,γ)46Sc reaction have been determined relative to the reference values of the 197Au(n,γ)198Au reaction, with σo,Au=98.65±0.09barn and Io,Au=1550±28barn. The present thermal neutron cross section has been determined to be σo,Sc=27.5±0.8barn. According to the definition of cadmium cut-off energy at 0.55eV, the present resonance integral cross section has been determined to be Io,Sc=12.4±0.7barn. The present results are compared with literature values and discussed.

Radar Remote Sensing Estimates of Waves and Wave Forcing at a Tidal Inlet

AbstractThe time and space variability of wave transformation through a tidal inlet is investigated with radar remote sensing. The frequency of wave breaking and the net wave breaking dissipation at high spatial resolution is estimated using image sequences acquired with a land-based X-band marine radar. Using the radar intensity data, transformed to normalized radar cross section σ0, the temporal and spatial distributions of wave breaking are identified using a threshold developed via the data probability density function. In addition, the inlet bathymetry is determined via depth inversion of the radar-derived frequencies and wavenumbers of the surface waves using a preexisting algorithm (cBathy). Wave height transformation is calculated through the 1D cross-shore energy flux equation incorporating the radar-estimated breaking distribution and bathymetry. The accuracy of the methodology is tested by comparison with in situ wave height observations over a 9-day period, obtaining correlation values R = 0.68 to 0.96, and root-mean-square errors from 0.05 to 0.19 m. Predicted wave forcing, computed as the along-inlet gradient of the cross-shore radiation stress was onshore during high-wave conditions, in good agreement (R = 0.95) with observations.

One-Group Cross-Section Generation for Monte Carlo Burnup Codes: Multigroup Method Extension and Verification

Allowing Monte Carlo (MC) codes to perform fuel cycle calculations requires coupling to a point depletion solver. In order to perform depletion calculations, one-group cross sections must be provided in advance. This paper focuses on generating accurate one-group cross-section values using Monte Carlo transport codes. The proposed method is an alternative to the conventional direct reaction rate tally approach, which requires substantial computational effort. The method presented here is based on the multigroup approach, in which pregenerated multigroup sets are collapsed with MC calculated flux. In our previous studies, we showed that generating accurate one-group cross sections requires their tabulation against the background cross section (σ0) to account for the self-shielding effect in the unresolved resonance energy range. However, in previous studies, the model used for the calculation of σ0 was simplified by relying on user-specified Bell and Dancoff factors.This work demonstrates that the one-group cross-section values calculated under the previous simplified model assumptions may not always agree with the directly tallied values. More specifically, the assumption is not universally applicable to the analysis of reactor systems with different neutron spectra and may be inaccurate when the number of energy groups is reduced (i.e., from tens of thousands to hundreds of groups). Therefore, the original background cross-section model was extended by implicitly accounting for the Dancoff and Bell factors.The method developed here reconstructs the correct value of σ0 by utilizing statistical data generated within the MC transport calculation by default. The proposed method was implemented in the BGCore code system. The one-group cross-section values generated by BGCore were compared with those tallied directly from the MCNP code. Very good agreement in the one-group cross-section values was observed. The method does not carry any additional computational burden, and it is universally applicable to the analysis of thermal as well as fast reactor systems. Adopting this multigroup methodology, which accounts for self-shielding, allows generation of highly accurate cross sections even if the number of energy groups is significantly reduced (to hundreds versus tens of thousands of groups). This reduction considerably improves the computational efficiency, which makes the analysis of large-scale reactor problems feasible.

Positron impact excitations of hydrogen atom embedded in weakly coupled plasmas: Formation of Rydberg atoms

Formation of Rydberg atoms due to 1s→nlm excitations of hydrogen, for arbitrary n, l, m, by positron impact in weakly coupled plasma has been investigated using a distorted-wave theory in the momentum space. The interactions among the charged particles in the plasma have been represented by Debye-Huckel potentials. Making use of a simple variationally determined wave function for the hydrogen atom, it has been possible to obtain the distorted-wave scattering amplitude in a closed analytical form. A detailed study has been made on the effects of plasma screening on the differential and total cross sections in the energy range 20–300 eV of incident positron. For the unscreened case, our results agree nicely with some of the most accurate results available in the literature. To the best of our knowledge, such a study on the differential and total cross sections for 1s→nlm inelastic positron-hydrogen collisions for arbitrary n, l, m in weakly coupled plasmas is the first reported in the literature.

Thermal neutron capture cross section and resonance integral of the 139La(n,γ)140La reaction

The thermal neutron capture cross section (σ0) and resonance integral cross section (I0) of the 139La(n,γ)140La reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural lanthanum and gold foils were exposed to pulsed neutrons at the Pohang neutron facility. One set of foils was irradiated directly and a second set of foils was shielded with a cadmium cover of 0.5mm thickness. The induced activities in the activated foils were measured by a γ-ray spectrometer based on a calibrated high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the epithermal neutron spectrum shape factor (α) was determined, and the corrections for the thermal neutron self-shielding (Gth), the resonance neutron self-shielding (Gepi), the γ-ray attenuation (Fg) and the γ-ray coincidence summing effects were made. The thermal neutron cross-section for the 139La(n,γ)140La reaction has been determined to be 9.16±0.36 barn, relative to the reference value of 98.65±0.09 barn for the 197Au(n,γ)198Au reaction. By assuming the cadmium cut-off energy of 0.55eV, the resonance integral cross section for the 139La(n,γ)140La reaction is 11.64±0.69 barn, which is determined relative to the reference value of 1550±28 barn for the 197Au(n,γ)198Au reaction. The measured results are compared with literature values and discussed.

Rydberg transitions for positron–hydrogen collisions: asymptotic cross section and scaling law

The dynamics of 1s → nlm excitations of hydrogen, for arbitrary n, l, m, by positron impact has been investigated using a distorted-wave theory in the momentum space. It has been possible to obtain the distorted-wave scattering amplitude in a closed analytical form. A detailed study has been made on the differential and total cross sections in the energy range 20–300 eV of incident positron. A simple law has been presented for obtaining asymptotic cross sections for excitation into different angular momentum states. To the best of our knowledge, such a study on the differential and total cross sections for 1s → nlm inelastic positron–hydrogen collisions using distorted-wave theory is the first reported in the literature.

Thermal neutron cross section and resonance integral measurements for the 133Cs(n,γ)134mCs reaction

The thermal neutron cross section (σ0) and the resonance integral cross section (I0) for the formation of the isomeric state 134mCs by the 133Cs(n,γ)134mCs reaction were experimentally determined by using an activation method with a single monitor 55Mn. In this study, each of analytical grade MnO2 and Cs2CO3 powders was diluted separately with Al2O3 powder to reduce neutron self-shielding effects, and then they were irradiated with and without a cadmium shield case in an isotropic neutron field of the 241Am–Be neutron source. The activities produced in the samples were measured by a high resolution γ-ray spectrometry with a calibrated HPGe detector. The necessary correction factors for γ-ray self-attenuation, true coincidence summing effects, thermal and resonance neutron self-shielding effects, and epithermal spectrum-shape factor were taken into account. The σ0 and I0 values were determined to be σ0=2.77±0.14b and I0=22.8±1.7b for the 133Cs(n,γ)134mCs reaction. These results are discussed and compared to the previous measurements and the evaluated data. The present σ0 value is close to some of the previously reported experimental and evaluated data within the uncertainty limits. However, the present I0 value was found to be about 28–51% smaller than other experimentally reported ones appeared in the literature. The measured resonance integral cross section value agrees well only with the newest experimental data obtained by Nakamura et al. (1999) for the 133Cs(n,γ)134mCs reaction.

Measurement of thermal neutron cross section and resonance integral for the 170Er(n, γ)171Er reaction by using a gold monitor

The thermal neutron cross section (σ0) and the resonance integral (I0) of the reaction 170Er(n,γ)171Er were measured by an activation method using a reaction 197Au(n,γ)198Au as a single comparator. The high-purity natural erbium (natEr) and gold (197Au) foils with and without Cd cover with the thickness of 0.5mm were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the activated foils were measured with a well calibrated coaxial HPGe detector. The thermal neutron cross section for the 170Er(n,γ)171Er reaction has been determined to be σ0=7.80±0.35 barn, relative to the reference value of 98.65±0.09 barn for the 197Au(n,γ)198Au reaction. By assuming the cadmium cut-off energy of 0.55eV, the resonance integral for the 170Er(n,γ)171Er reaction is I0=40.4±2.8 barn, which is determined relative to the reference value of 1550±28 barn for the 197Au(n,γ)198Au reaction. In order to improve the accuracy of the experimental results the epithermal neutron spectrum shape factor (α) was determined, and the necessary corrections for the counting loss caused by γ-ray attenuation (Fg), the thermal neutron shelf-shielding (Gth), the resonance neutron self-shielding (Gepi) effects, the γ-ray coincidence summing effect, as well as neutron flux fluctuation. The present results are compared with the reference data and discussed.

Comparison of IUPAC k 0 values and neutron cross sections to determine a self-consistent set of data for neutron activation analysis

Abstract Independent databases of nuclear constants for Neutron Activation Analysis (NAA) have been independently maintained by the physics and chemistry communities for many year. They contain thermal neturon cross sections σ 0, standardization values k 0, and transition probabilities P γ . Chemistry databases tend to rely upon direct measurements of the nuclear constants k 0 and P γ which are often published in chemistry journals while the physics databases typically include evaluated σ 0 and P γ data from a variety of experiments published mainly in physics journals. The IAEA/LBNL Evaluated Gamma-ray Activation File (EGAF) also contains prompt and delayed γ-ray cross sections σ γ from Prompt Gamma-ray Activation Analysis (PGAA) measurements that can also be used to determine k 0 and σ 0 values. As a result several independent databases of fundamental constants for NAA have evolved containing slightly different and sometimes discrepant results. An IAEA CRP for a Reference Database for Neutron Activation Analysis was established to compare these databases and investigate the possibilitiy of producing a self-consistent set of σ 0, k 0, σ γ , and P γ values for NAA and other applications. Preliminary results of this IAEA CRP comparison are given in this paper.

Relative Calibration Using Natural Terrestrial Targets: A Preparation Towards Oceansat-2 Scatterometer

Scatterometer instruments transmit a series of microwave pulses and measure the returned echo to determine the normalized radar cross section (σ0) over the target to derive the near-ocean-surface wind vector. Accuracy of the derived wind vector over the data sparse oceans therefore depends on the accuracy of σ0 measurement. For this purpose, accurate calibration of the scatterometer is required. As a preparation toward calibration of the Oceansat-2 mission, of the Indian Space Research Organisation, a relative calibration technique has been proposed in this study by selecting homogeneous areas over the globe with isotropic radar response and temporally stable signature of σ0. For this purpose, the daily averaged σ0 and Level-2A (L2A) σ0 measurements of the QuikSCAT scatterometer have been used. Analyzing the monthly mean and standard deviation in σ0 for the period of 2005-2006, several regions are chosen which have a quasi-isotropic radar response and minimal temporal variation in σ0. The analysis shows that the selected areas over Antarctica and Greenland with permanent ice covers have temporally stable signatures of σ0. The regions like the Amazon forests and parts of Australia also show high temporal stability of σ0 but greater standard deviation than the snow-covered areas. The QuikSCAT L2A data have also been used to study the day-night variation and azimuthal dependence of the σ0 over these targets. The present work demonstrated that quasi-uniform natural sites such as Sahara, Amazon forest, Kutch, Greenland region, and Antarctica region, covering wide dynamic range of σ0, can be used for the purpose of calibration.