Proton elastic scattering and proton induced γ-ray emission cross-sections on Na from 2 to 5 MeV

Differential cross-sections for proton elastic scattering on sodium and for γ-ray emission from the reactions ²³Na(p,p′γ)²³Na (E_γ = 440 keV and E_γ = 1636 keV) and ²³Na(p,α′γ)²⁰Ne (E_γ = 1634 keV) were measured for proton energies from 2.2 to 5.2 MeV using a 63 μg/cm² NaBr target evaporated on a self-supporting thin C film.The γ-rays were detected by a 38% relative efficiency Ge detector placed at an angle of 135° with respect to the beam direction, while the backscattered protons were collected by a Si surface barrier detector placed at a scattering angle of 150°. Absolute differential cross-sections were obtained with an overall uncertainty estimated to be better than ±6.0% for elastic scattering and ±12% for γ-ray emission, at all the beam energies.To provide a convincing test of the overall validity of the measured elastic scattering cross-section, thick target benchmark experiments at several proton energies are presented.     

Tables for reaction gamma-ray spectroscopy part II. A = 21 to A = 32

Observed γ-ray transitions from bound and nearly bound levels of all known nuclides in the mass range A = 21 to A = 32 are tabulated for use in reaction (on-line, in-beam) γ-ray spectroscopy. The tables present energies, spins, and parities of the nuclear levels, the transition (photopeak) energy corrected for recoil, the corresponding Compton edge and escape peaks, as well as competing decays, mean lives, and branching ratios when known. The information is arranged in order of both increasing γ-ray energy and nuclide mass number. The literature cutoff date is Aug. 15, 1974.     

Tables for reaction gamma-ray spectroscopy part III. A = 33 to A = 44

Observed γ-ray transitions from bound and nearly bound levels of all known nuclides in the mass range A = 33 to A = 44 are tabulated for use in reaction (on-line, in-beam) γ-ray spectroscopy. The tables present energies, spins, and parities of the nuclear levels, the transition (photopeak) energy corrected for recoil, the corresponding Compton edge and escape peaks as well as competing decays, mean lives, and branching ratios when known. The information is arranged in order of both increasing γ-ray energy and nuclide mass number. The literature cutoff date is Oct. 15, 1975.     

Tables for reaction gamma-ray spectroscopy part I. A = 6 to A = 20

Observed and possible γ-ray transitions from bound and nearly bound levels of all known nuclides up to A = 20 are tabulated for use in reaction (on-line, in-beam) γ-ray spectroscopy. The tables present energies, spins and parities of the nuclear levels, the transition (photopeak) energy corrected for recoil, the corresponding Compton edge and escape peaks, as well as competing decays, mean life and branching ratios when known. The information is arranged in order of both increasing γ-ray energy and nuclide mass number.     

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of 167 Er

The neutron capture cross sections and capture γ-ray spectra of ¹⁶⁷Er were measured in the neutron energy region of 10 to 90keV and at 550 keV. Using a neutron time-of-flight method with a 1.5-ns pulsed neutron source by the ⁷Li(p, n)⁷Be reaction, the measurement was performed by detecting prompt γ rays from an enriched capture sample with a large anti-Compton Nal(Tl) spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using the standard capture cross sections of ¹⁹⁷Au. The present results were compared with the evaluated values of ENDF/B-VI and the previous measurement. The present measurement at 550 keV was the first one. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was clearly observed around 3 MeV in the γ-ray spectra and the energy position of the shoulder was consistent with the systematics obtained in our previous work. The multiplicities of the observed γ rays were derived from the γ-ray spectra.     

Method of Measuring Boron-10 Depletion in Control Blade

The neutron capture cross sections and capture γ-ray spectra of ^143,145,146Nd were measured in the neutron energy region of 10 to 90 keV and at 550 keV. A neutron time-of-flight method was adopted with a 1.5-ns pulsed neutron source by the ⁷Li(p, n)⁷Be reaction and with a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained with the error of about 5% by using the standard capture cross sections of ¹⁹⁷Au. The evaluated values of JENDL-3.2 and previous measurements were compared with the present results. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was observed around 2 MeV in the γ-ray spectra of ^145,146Nd, and the energy position of the shoulder was consistent with the systematics obtained in our previous work.     

Measurement of ke V-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of 147,148,149,150,152,154Sm

The neutron capture cross sections and capture γ-ray spectra of ^{147,148,149,150,152,154}Sm were measured in the neutron energy region of 10 to 90 keV and at 550 keV. A neutron time-of-flight method was adopted with a 1.5-ns pulsed neutron source by the ⁷Li(p, n)⁷Be reaction and with a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained with the error of about 5% by using the standard capture cross sections of ¹⁹⁷Au. The present results were compared with the evaluated values of JENDL-3.2 and previous measurements. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was clearly observed around 3 MeV in the γ-ray spectra of ^150,152,154Sm, and the energy position of the shoulder was consistent with the systematics obtained in our previous work.     

Measurement of Gamma-Ray Production Cross Sections of Iron for Incident Neutron Energies between 6 and 33 MeV

Measurement of differential γ-ray production cross sections, i.e. (n, x γ) cross sections, of Fe was made for neutron energies from 6 to 33 MeV. Neutrons used in the experiment were white neutrons produced with (p, n) reactions by 35 MeV protons using a thick Be target. The neutron energy was analyzed by the time-of-flight method and bunched into 3 MeV wide energy bins, for each of which the spectrum of secondary γ-rays produced in an Fe sample was measured by a BGO scintillator at an angle of 144° to the neutron beam direction.

The obtained (n, xγ) cross sections agreed well with other data and the evaluated data file of ENDF/B-IV at neutron energies below 15 MeV where data were existing. The JENDL-3 file overestimated the γ-ray spectra at γ-ray energies of 3 to 7 MeV. The present work newly provided the data in the neutron energy range above 20 MeV. The GNASH calculation made by Young reproduced the measured data fairly well even at these higher energies.     

Strengths of gamma-ray transitions between bound states of A = 21–44 nuclei

The present tables classify the strengths of about 600 γ-ray transitions between bound states according to character (electric or magnetic), multipolarity, and isospin forbiddenness. The input material (energies, J^π-values, isobaric spins, lifetimes, branching and mixing ratios) has been provided by a recent review of the A = 21–44 nuclei. The transitions listed here are restricted to those for which the J^π- and T-values of initial and final state have been determined unambiguously (on a 99.9% probability basis) and for which the error in the strength does not exceed 50%.From a comparison of mirror transitions, additional information has been obtained on isoscalar M1 and isovector E2 transitions.From the strength distributions, a set of recommended upper limits for γ-ray strengths has been derived.     

Calculation of Gamma-Ray Production Cross Sections at Neutron Energies of 1–20 MeV

In order to prepare the p-ray data library requested in a design of fission and fusion reactors, γ-ray production cross sections and spectra of Al, Si, Ca, Fe, Ni, Cu, Nb, Ta, Au and Pb have been obtained at the neutron energies of 1–20 MeV, using a spin-dependent multi-step evaporation model. Calculations include dipole and quadrupole transition without the distinction between electric and magnetic process, and take explicit account of the role of yrast levels. The effects of the yrast levels and γ-ray strength function upon γ-ray production are also investigated in relation to particle emission. At the incident neutron energies where (n,n^γ ) and/or (n,2^nγ ) reactions are dominant, the present model is shown to be able to predict the production of secondary γ-rays (<9.0 MeV) from medium-heavy to heavy nuclei with reasonable accuracy.     

Albedo Component of Gamma-Ray Streaming through Straight Cylindrical Ducts

An experimental study was performed to investigate the effect of γ-ray streaming through cylindrical steel and lead ducts having various lengths and radii. In the experiment, ⁶⁰Co and ¹³⁷Cs point sources, and small sized detector (pulse dosimeter with plastic scintillator) was adopted, source and detector being located at the centers of opposite duct mouths. The albedo-to-direct component ratio is about 30% for steel ducts and 10% for lead at γ-ray energies of 1.25 and 0.661 MeV, with L/R ₀~10.

The measured results were compared with those calculated by the Monte Carlo method; they showed a good agreement. Consequently, the prediction of doses for straight cylindrical ducts having various length-to-radius ratios can be made by the procedures based on the Monte Carlo calculations.     

Measurement of keV-neutron capture cross-sections and capture γ-ray spectra of Fe and Fe

The neutron capture cross-sections and the capture γ-ray spectra of ⁵⁶Fe and ⁵⁷Fe have been measured in the neutron energy range from 10 to 90 keV. Pulsed keV-neutrons were produced from the ⁷Li(p,n)⁷Be reaction by bombarding a lithium target with a 1.5-ns bunched proton beam from a 3 MV Pelletron accelerator. The incident neutron spectrum on the capture sample was measured using a time-of-flight method with a ⁶Li-glass detector. The capture γ-rays emitted from an iron or standard gold sample were detected with a large anti-Compton NaI(Tl) spectrometer. The capture yield of the iron or gold sample was obtained by applying a pulse-height weighting technique to the corresponding capture γ-ray pulse-height spectrum. The capture cross-sections of ^56,57Fe were derived with errors less than 5% using the standard capture cross-sections of ¹⁹⁷Au. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. The present results for the capture cross-sections were compared with the previous measurements and the evaluated values of ENDF/B-VII.0 and JENDL-3.3. The Maxwellian-averaged capture cross-sections of ⁵⁶Fe and ⁵⁷Fe at 30 keV are derived as 12.22 ± 2.06 mb and 44.48 ± 7.56 mb, respectively.     

Evaluation of Neutron Capture Gamma-Ray Spectra in Hafnium and Tantalum

A method has been developed for evaluation of neutron capture γ-ray spectrum. It couples measured intensities of primary and secondary discrete—-ray with a γ-ray cascade model to calculate the unresolved part of the capture spectrum, and adds the discrete part and the unresolved part to obtain the whole spectrum. The cascade model uses the level density formula proposed by Gilbert & Cameron and the Brink & Axel form of El γ-ray profile function with a modification. This method was applied to thermal neutron capture spectra in six hafnium isotopes and ¹⁸¹Ta and was extended also to non-thermal capture spectra in ¹⁸¹Ta for 0.25 and 0.5 MeV neutrons with empirical assumptions. The calculated results were compared with experiments and agreement was good not only in terms of the gross structure, but also in terms of the fine structure which appears at high and low γ-ray energies.     

Studies on absorption coefficients of dual-energy γ-rays and measuring error correction for multiphase fraction determination

In tiffs article, principle and mathematical method of determining the phasc fractions of multiphase flows by using a dual-energy γ-ray system have been described. The dual-energy γ-ray device is composed of radioactive isotopes of ^241Am and ^137Cs with γ-ray energies of 59.5 and 662 keV, respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The modified arithmetic is beneficial to removing the extra Compton scattering from the measured value. The result shows that the dual-energy γ-ray technique can be used in thrce-phase flow with average accuracy greater than 95%, which enables us to determine phase fractions almost independent of the flow regime. Improvement has been achicved on measurement accuracy of phase fractions.     

Calculation and analysis of n+Zr reactions in the En ⩽ 250 MeV energy range

All of reaction cross sections, angular distributions, energy spectra, γ-ray production cross sections, and the double differential cross section for neutron, proton, deuteron, triton, helium and alpha emission are calculated and analyzed for n+^{90,91,92,94,96,nat}Zr at incident neutron energies from 0.1 to 250 MeV. The optical model, intranuclear cascade model, the unified Hauser–Feshbach theory and the exciton model which included the improved Iwamoto–Harada model are used. Theoretical calculated results are compared with existing experimental data and other evaluated data from ENDF/B-VI.8, ENDF/B-VII.0 and JENDL-3.3. The optical model potential parameters are obtained according to the experimental data of total, nonelastic cross sections and elastic scattering angular distributions.     

Strengths of gamma-ray transitions in A = 6–44 nuclei (III)

The present tables list the strengths (in Weisskopf units) of over 2400 γ-ray transitions in A = 6–44 nuclei, classified according to character (electric or magnetic, multipolarity, isospin forbiddenness). Selected transitions from unbound states are included. The strengths for isovector E1 and M1 transitions (E1_IV and M1_IV) show a marked decrease with A. Strengths depended very little on the excitation energy of the initial state. The new data incorporated in the table haave not given rise to changes in the recommended upper limits (RUL) for γ-ray strengths presently in use. The only exception is the (spectroscopically unimportant) RUL for E1_IV transitions which should be raised from 0.1 to 0.3 W.u. for A = 6–20 nuclei.     

Proton induced γ-ray emission yields for the analysis of light elements in aerosol samples in an external beam set-up

The PIXE technique is a reliable tool for the characterisation of thin aerosol samples, but it can underestimate the lightest measurable elements, like Na, Mg, Al, Si and P, owing to the absorption of their X-rays inside the sample. The PIGE technique is a valid help to determine corrections for such effect: in order to perform PIGE measurements relative to thin reference standards in an external beam set-up, we measured, at the external beam facility of the Tandetron accelerator of the LABEC laboratory in Florence, the γ-ray yields as a function of the proton beam energy for the reactions ¹⁹F(p,p′γ)¹⁹F (E_γ = 110 and 197 keV), ²³Na(p,p′γ)²³Na (E_γ = 440 keV) and ²⁷Al(p,p′γ)²⁷Al (E_γ = 843 and 1013 keV), in the proton energy range from 3 to 5 MeV. The measured yields are shown, and the determined most suitable energies for performing PIGE quantification of Na and Al are reported, together with the corresponding minimum detection limits (MDLs). The results of some test on PIGE accuracy and an evaluation of self-absorption effects in PIXE measurements on thin aerosol samples are also presented.     

Decay Heat Calculations Based on Theoretical Estimation of Average Beta- and Gamma-Energies Released from Short-Lived Fission Products

Fission product decay heat of ²³⁵U was calculated for short cooling-time on the basis of a preliminary version of a new decay data library recently completed by the Japanese Nuclear Data Committee. It was shown that a full adoption of recent publications of decay schemes to derive average energies of β- and γ-rays, ē_β, and ē_γ, leads to a large underestimation of the γ-ray component of the decay heat and to an overestimation of the β-ray component. In order to remedy this, theoretical values of ē_β and ē_γ were introduced for high Q-value decays, which were obtained with a gross theory of β-decay. It improved remarkably the agreement between calculation and experiment not only for the ²³⁵U decay heat but for ²³⁹Pu and ²⁴¹Pu as well. It was concluded that a large part of decay schemes recently published for high Q-value nuclides are inappropriate to use in calculations of ē_β and ē_γ, because they fail to reproduce the effect of β- strengths at high excitations, which makes ē_β small and ē_γ large. The use of the gross theory introduces this effect correctly into the values of ē_β and ē_γ and, hence, leads to a quite good prediction of both β- and γ-ray components of the decay heat.     

Novel methodology for the quantitative assay of fissile materials using temporal and spectral β-delayed γ-ray signatures

An analytical model for the generation of β-delayed γ-ray spectra following thermal-neutron-induced fission of mixed samples of ²³⁵U and ²³⁹Pu is presented. Using an energy-dependent figure-of-merit to designate the spectral regions employed in the assay, the unique temporal β-delayed γ-ray signatures are utilized to determine the fraction of ²³⁹Pu in a mixed U-Pu sample. By evaluating the β-delayed γ-ray temporal signatures of both ²³⁵U and ²³⁹Pu within a 3 keV energy bin, traditional sources of systematic uncertainty in quantitative assay using β-delayed γ-ray signals, such as self-attenuation of the sample and energy-dependent γ-ray detection efficiency, are significantly reduced. The effects of the time-dependent Compton-continuum and growth of longer-lived nuclides on the quantitative assessment are explored. This methodology represents a promising extension of the conventional means of analysis for quantitative assay of fissile materials using β-delayed γ-ray signatures.     

Prompt gamma rays from thermal-neutron capture

A catalog of γ-rays emitted following thermal-neutron capture in natural elements is presented. In Table I, γ-rays are arranged in order of increasing energy. Each line contains the γ-ray energy, intensity, element identification, thermal-neutron radiative-capture cross section, and the energies and intensities of two of the more abundant γ-rays associated with that element. In Table II, γ-rays are arranged by element and γ-ray energy; energy uncertainty and γ-ray intensity are given. The catalog is designed for use in high-resolution analytical prompt γ-ray spectroscopy.