Measurement of (d,p) and (d,α) differential cross-sections for aluminum

The differential cross-sections for ²⁷Al(d,p_{0+1,2+3,4,5+6})²⁸Al and ²⁷Al(d,α_0,1,2,3,4)²⁵Mg have been measured in the energy ranges from 1.3 to 2.3 MeV and from 1.5 to 2.4 MeV, respectively at the laboratory angle of 150°. The obtained results are compared with data published in the literature. Discrepancies between new and previously acquired data are discussed. The cross-sections measured in the present work were uploaded to the IBANDL data base (www-nds.iaea.org/ibandl/).     

Measurement of differential cross-sections and widths of resonances in S(p,p′γ) S reaction in the 3.0-4.0 MeV region

The paper reports the widths and differential cross-sections of resonances at 3.089, 3.379 and 3.717 MeV in the ³²S(p,p′γ)³²S nuclear reaction. The cross-sections are computed at 0° and 90° angles (relative to the beam direction) from thick target excitation curves constructed by measuring 2230 keV γ-rays, characteristic of the reaction. The differential cross-sections of resonances are about 18, 64 and 70 mb/sr respectively at 0° angle and decrease by about half around an angle of 90°. The first resonance, the sharpest among the three, exhibits a width of about 400 eV while those at 3.379 and 3.717 MeV are in 1.0-1.5 keV range. The widths of the resonances are extracted from the respective thick target excitation curves by an interquartile separation method and also by simulating their leading edges. A study of thick target yields in the 3.0-4.0 MeV proton energy region for several sulphide forming elements shows the absence of any significant interference. These resonances, as a result, can be effectively utilised for sensitive and high resolution depth profile measurements of sulphur in films and materials surfaces.     

Depth-profiling of implanted 28Si by (α,α) and (α,p0) reactions

Silicon nanocrystals enclosed in thin films (Si quantum dots or Si QDs) are regarded to be the cornerstone of future developments in new memory, photovoltaic and optoelectronic products. One way to synthesize these Si QDs is ion implantation in SiO₂ layers followed by thermal annealing post-treatment.Depth-profiling of these implanted Si ions can be performed by reactions induced by α-particles on ²⁸Si. Indeed, for high incident energy, nuclear levels of ³²S and ³¹P can be reached, and cross-sections for (α,α) and (α,p₀) reactions are more intense. This can help to increase the signal for surface silicon, and therefore make distinguishing more easy between implanted Si and Si coming from the SiO₂, even for low fluences.In this work, (α,α) and (α,p₀) reactions are applied to study depth distributions of 70 keV ²⁸Si⁺ ions implanted in 200 nm SiO₂ layers with fluences of 1 × 10¹⁷ and 2 × 10¹⁷ cm^?2. Analysis is performed above E_R = 3864 keV to take advantage of resonances in both (α,α) and (α,p₀) cross-sections. We show how (α,p₀) reactions can complement results provided by resonant backscattering measurements in this complex case.     

Semi-empirical systematics for the cross-sections of the reactions (n,α), (n,p) and (n,2n) at 14.5 MeV neutrons on the basis of experimental data measured by Lanzhou University

Three new semi-empirical formulae for the calculation of the (n,α), (n,p) and (n,2n) cross-sections at neutron energy 14.5 MeV were obtained on the basis of experimental data measured by Lanzhou University. Derived from the statistical model with consideration of the Q-value dependence, the new formulae include three, three and four parameters for (n,α), (n,p) and (n,2n) reactions, respectively. The obtained relations are compared with other recently proposed systematics based on the statistical model as well as on the asymmetry parameter dependence.     

Measurements of activation cross sections for Lu(n, α)Tm,Lu(n, α)Tm and Lu(n, p)Yb reactions induced by neutrons around 14 MeV

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

The 11B(p,α0)8Be nuclear reaction and 11B(p,p)11B backscattering cross sections for analytical purposes

The ¹¹B(p,α₀)⁸Be nuclear reaction and the ¹¹B(p,p)¹¹B backscattering cross sections were measured at a laboratory scattering angle of 165° in the energy range from 1700 to 2700 keV with an absolute accuracy of about 7%. The cross section values were derived by using the simultaneously measured RBS spectra of the protons backscattered from a thin gold layer. The measured cross section values are compared with X-ray photoelectron spectroscopy (XPS) and heavy ion elastic recoil detection analysis (HERDA) results of amorphous hydrogenated boron/carbon (a-B:C:H) layers. The cross section data are presented in graphical and tabular form.     

Applications of (n,p) and (n, α) reactions and a backscattering technique to fusion reactor materials,archeometry, and nuclear spectroscopy

Depth profiles of He, Li and B are determined by ³He(n, p)T, ⁶Li(n, α)T and ¹⁰B(n, α)⁷Li reactions with thermal neutrons at the high flux reactor of the ILL, Grenoble. The behaviour of Li in Be is examined with respect to future fusion reactors. Range profiles of 70–300 keV Li⁺ are measured and found to agree with theory based on Lindhard-Scharff electronic stopping and Molière potential. Li becomes mobile in Be above 100°C. Further, B and Li distributions in glaze of ancient pottery are examined for studying ancient production techniques. It is found that all examined samples (of Islamic, Thai and North American provenience) show Li and B concentrations which are enriched relative to the original material. Li is mostly depleted in a surface layer of 0.1–1.6 μm half-width due to various burning conditions.In experimental nuclear physics, gas cells are now often replaced by thin foils with implanted gas. In many cases the knowledge of the concentration profile is required, and is presently evaluated for the case of ³He in Ni and Au with the (n, p) reaction. This is compared to results obtained by a special Rutherford backscattering technique yielding good agreement.     

Cross-section measurements for the (n,p) and (n,α) reactions on 23Na and for the (n,p) reaction on 26Mg at the neutron energies from 13.6 to 14.9 MeV

Cross sections were measured at neutron energies from 13.6 to 14.9 MeV for the reactions ²³Na(n,p)²³Ne and ²³Na(n,α)²⁰F, and ²⁶Mg(n,p)²⁶Na leading to short-lived products. The production of short-lived nuclei and the spectra accumulation have been carried out by cyclic activation method. Corrections were made for the effects of gamma ray attenuation, coincidence summing, pulse pile-up, dead time, neutron flux fluctuations and scattered low energy neutrons.     

Isomeric yield ratios for the formation of Sc in the Sc(γ,n), Ti(γ,xnp), Fe(γ,xn5p) and Cu(γ,xn8p) reactions with 2.5 GeV bremsstrahlung

We measured the isomeric yield ratios for the ^44m,gSc isomeric pairs produced from four different photonuclear reactions ⁴⁵Sc(γ,n)^44m,gSc, ^natTi(γ,xn1p)^44m,gSc, ^natFe(γ,xn5p)^44m,gSc, and ^natCu(γ,xn8p)^44m,gSc by using the activation method. The high purity natural Sc, Ti, Fe, and Cu metallic foils in disc shape were irradiated with uncollimated 2.5 GeV bremsstrahlung beams of the Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometry with a calibrated high-purity Germanium (HPGe) detector. In order to improve the accuracy of the experimental results the necessary corrections were made in the gamma activity measurements and data analysis. The obtained isomeric yield ratios for the ⁴⁵Sc(γ,n)^44m,gSc, ^natTi(γ,xn1p)^44m,gSc, ^natFe(γ,xn5p)^44m,gSc and ^natCu(γ,xn8p)^44m,gSc reactions are 0.25 ± 0.03, 0.43 ± 0.05, 1.38 ± 0.14, and 1.89 ± 0.21, respectively. The present result for the ^natCu(γ,xn8p)^44m,gSc reaction is in good agreement with the existing data. Our results for the ⁴⁵Sc(γ,n)^44m,gSc, ^natTi(γ,xn1p)^44m,gSc, and ^natFe(γ,xn5p)^44m,gSc reactions are the first measurements at 2.5 GeV bremsstrahlung. The obtained results are compared with the corresponding values found in the literature. The relation between the isomeric yield ratios and the complexity of the photonuclear reactions is discussed.     

Measurements of activation cross sections of (n,p) and (n, α) reactions in the energy range of 3.5–5.9 MeV using a deuterium gas target

Activation cross sections of (n, p) and (n, α) reactions were measured by means of the activation method in the neutron energy range of 3.5–5.9 MeV using a deuterium gas target. The irradiated target isotopes were ²⁷Al, ^28,29Si, ⁴¹K, ⁵¹V, ⁶¹Ni, ⁶⁵Cu, ^64,67Zn, ⁶⁹Ga, ⁷⁹Br, ⁹²Mo and ⁹³Nb. The cross sections of the ²⁹Si(n, p) ²⁹Al, ⁶⁷Zn(n, p) ⁶⁷Cu, ⁶⁹Ga(n, p) ^69mZn, ⁷⁹Br(n, p) ^79mSe, and ⁶⁹Ga(n, α) ⁶⁶Cu reactions were obtained for the first time in the studied energy range. The d-D neutrons were generated by the deuterium gas target at the Van de Graaff accelerator (KN-VdG) at Nagoya University. All cross section values were determined relative to those of the ¹¹⁵In(n, n′)^115mIn reaction. The activities induced by the low-energy neutrons were corrected. For the corrections, the neutron spectra and mean neutron energies at the irradiation positions were calculated taking into account the energy loss of incident deuterons, the angular differential cross section of the d-D reaction and the solid angle subtended by the sample. The systematics of the (n, p) reactions at the neutron energy of 5.0 MeV in the mass range between 27 and 92 were proposed for the first time. This systematics can predict the cross sections within an accuracy of a factor of 1.6.     

Measurement of thick-target gamma-ray production yields of the 7Li(p,p′)7Li and 7Li(p, γ)8Be reactions in the near-threshold energy region for the 7Li(p,n)7Be reaction

The gamma-ray production reactions, ⁷Li(p, p′)⁷Li and ⁷Li(p, γ)⁸Be, occur along with the neutron production reaction ⁷Li(p, n)⁷Be in a p-Li neutron source. These gamma-ray production reactions contribute to a patient's absorbed dose in boron neutron capture therapy (BNCT) when using a neutron beam from the ⁷Li(p, n)⁷Be reaction. The present work experimentally determined the thick-target gamma-ray production yields of the ⁷Li(p, p′)⁷Li and ⁷Li(p, γ)⁸Be reactions at incident proton energies of 1.670 and 1.870 MeV. The present results were compared with previous measurements. The gamma-ray production yield of ⁷Li(p, p′)⁷Li was measured to be 30%–50% smaller than as reported by previous studies. For the ⁷Li(p, γ)⁸Be reaction, the present thick-target yield is 30% smaller than one estimated from cross-section data measured in previous studies. The results must be included in future dose evaluation for BNCT using a p–Li neutron source.     

Measurement of thermal neutron cross-sections and resonance integrals for Hf(n,γ)Hf and Hf(n,γ)Hf reactions at the Pohang neutron facility

The thermal-neutron cross-sections and the resonance integrals for the ¹⁷⁹Hf(n,γ)^180mHf and the ¹⁸⁰Hf(n,γ)¹⁸¹Hf reactions have been measured by the activation method. The high purity Hf and Au metallic foils within and without a Cd shield case were irradiated in a neutron field of the Pohang neutron facility. The gamma-ray spectra from the activated foils were measured with a calibrated p-type high-purity Ge detector.In the experimental procedure, the thermal neutron cross-sections, σ₀, and resonance integrals, I₀, for the ¹⁷⁹Hf(n,γ)^180mHf and the ¹⁸⁰Hf(n,γ)¹⁸¹Hf reactions have been determined relative to the reference values of the ¹⁹⁷Au(n,γ)¹⁹⁸Au reaction, with σ₀ = 98.65 ± 0.09 barn and I₀ = 1550 ± 28 barn. In order to improve the accuracy of the experimental results, the interfering reactions and necessary correction factors were taken into account in the determinations. The obtained thermal neutron cross-sections and resonance integrals were σ₀ = 0.424 ± 0.018 barn and I₀ = 6.35 ± 0.45 barn for the ¹⁷⁹Hf(n,γ)^180mHf reaction, and σ₀ = 12.87 ± 0.52 barn and I₀ = 32.91 ± 2.38 barn for the ¹⁸⁰Hf(n,γ)¹⁸¹Hf reaction. The present results are in good agreement with recent measurements.     

Hydrogen-induced disproportionation characteristics of Zr(1 − x)Hf(x)Co(x = 0, 0.1, 0.2 and 0.3) alloys

Doping hafnium to partially substitute zirconium in ZrCo is a promising strategy to improve the ability to resist hydrogen-induced disproportionation. Herein, Zr(1 ? x)Hf(x)Co(x = 0,0.1,0.2, and 0.3) alloys were fabricated by arc melting and the effect of hafnium substitution ratio and temperature on their hydrogen-induced disproportionation was studied. Additionally, the disproportionated products were characterized by XRD, DSC and TDS. Results showed that disproportionation rate and the extent of disproportionation decreased with hafnium substitution ratio increasing from 0 to 30% and increased with temperature increasing from 400 °C to 550 °C. It was exciting that Zr0.7Hf0.3Co alloy had much better ability of anti-disproportionation than ZrCo in hydrogen pressure of about 200 kPa when temperature increasing from 400 °C to 550 °C, which was practical for tritium application.     

Interaction of 〈1 0 0〉 loops with Carbon atoms and 〈1 0 0〉 dislocations in BCC Fe: An atomistic study

We apply atomistic simulations using the so called ‘metallic-covalent bonding’ interatomic model for the Fe–C system to study mobility of 〈1 0 0〉 interstitial dislocation loops, known to form in Fe and Fe-based ferritic alloys under irradiation, and their interaction with Carbon atoms. Carbon atoms represent an effective trap for the 〈1 0 0〉 loops with a binding energy of the order of 1 eV. The mobility of the loops is studied using the dislocation – loop drag model. From this model the activation parameters are identified and discussed.     

Measurement of isomeric yield ratios for 90Zr(γ, n)89m,gZr, natZr(γ, xn1p)86m,gY, and 89Y(γ, xn)87m,g,86m,gY reactions with 50-, 60-, and 70-MeV bremsstrahlung

We measured the isomeric yield ratios in the photonuclear reactions of ^natZr(γ, n)^89m,gZr, ^natZr(γ, xn1p)^86m,gY, and ⁸⁹Y(γ, xn)^87m,g,86m,gY by the activation method. The high-purity natural Zr and Y metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator at Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometric system consisting of a high-purity germanium detector and a multichannel analyzer. The obtained isomeric yield ratios in the formation of ^89m,gZr, ^87m,gY, and ^86m,gY are compared with the corresponding values found in the literature. The measured isomeric yield ratios at the bremsstrahlung energies of 50-, 60-, and 70-MeV are the first measurement except ⁸⁷Y at 50-MeV bremsstrahlung.     

Excitation functions of (n, α) reaction cross-sections for some important isotopes from threshold to 20 MeV

The (n, α) reaction cross-sections from threshold to ∼20 MeV on some important nuclides ⁴²Ca, ^50,53Cr, ^56,57Fe, ^58,62Ni, and ^63,65Cu involved in the reactor shielding design have been calculated using the Hauser–Feshbach statistical model with preequilibrium effects by involving PCROSS option in Empire 2.19. The transmission coefficients for neutrons in the entrance channel are calculated using the optical model potential of Koning. In the exit channel optical model potential of Avrigeanu has been used. The experimental values have been chosen carefully for all the isotopes, from EXFOR data base. The calculations are compared with existing experimental data as well as with evaluated data files (ENDF/B-VI.0 and JENDL-3.3). A good agreement between the calculated and experimental data validates the nuclear model approaches with increased predictive power to supplement and extend the nuclear database that is required for several applications.     

Measurement of Double Differential Cross Sections for ~(39)K(n,α)~(36)Cl Reaction

Introduction ~(39)K(n,α)~(36)Cl reaction data are important in nuclear engineering, nuclear medicine, astrophysics as well as in the study of nuclear mechanism. As we know, experimental data for ~(39)K(n,α)~(36)Cl reaction are scanty and there is no double differential datum. The double differential cross section data of ~(39)K(n,α)~(36)Cl reaction were measured at 4.41±0.26, 5.46±0.21 and 6.52±0.16 MeV using a gridded ionization chamber (GIC).