Measurement of Be-profiles by the 9Be(p,α)6Li reaction

The use of the ⁹Be(p,α)⁶Li (E_p = 330 keV) reaction as a tool for the profiling of implanted Be is described.Pile-up problems, caused by elastically scattered particles, requires a mylar foil to be introduced in front of the particle detector. This causes severe straggling and thus loss of depth resolution. A deconvolution technique, which is based on an iterative procedure, is described. With it, profiles are reconstructed with a depth resolution of 300 Å.The present technique was used to assess the diffusion of Be implanted into InSb and GaAs during annealing. Pronounced diffusion accompanied by Be loss was found for GaAs (T_ann = 1113 K, T_melt = 1511 K), while hardly any changes in Be profiles for InSb (T_ann = 670 K, T_melt = 798 K) could be detected.     

Calculation of cross sections for metastable state production in the (n, γ), (n,n′), (n, 2n) and (n, 3n) reactions of 93Nb

Toward the revision of ⁹³Nb data in the Japanese Evaluated Nuclear Data Library JENDL-4.0, we calculated cross sections for metastable state production (MSP) in the (n, γ), (n, n′), (n, 2n) and (n, 3n) reactions in the incident energy (E_n) range from 7 keV to 20 MeV. The cross sections were evaluated using nuclear reaction models such as the spherical optical model, the multi-step statistical model, preequilibrium models, and the distorted-wave Born approximation (DWBA). By adjusting parameters of nuclear level densities, we could obtain the MSP cross sections which are almost consistent with the experimental data.     

Measured activation cross-section ratios for 7Li(n,n′t)4He and 60Ni(n,p)60Co relative to 27Al(n,p)27Mg and 27Al(n,α)24Na in the 9Be(d,n)10B thick-target neutron spectrum at 7-MeV deuteron energy

The activation method is used to measure integral cross-section ratios for ⁷Li(n,n′t)⁴He and ⁶⁰Ni(n,p)⁶⁰Co relative to ²⁷Al(n,p)²⁷Mg and ²⁷Al(n,α)²⁴Na in the neutron spectrum produced by bombarding a thick Be metal target with 7-MeV deuterons. The results of these measurements are found to support the evaluated differential cross-section values from ENDF/B-V (1979, 1981).     

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.     

Three-dimensional lithium microanalysis by the 7Li(p, α) reaction

In order to investigate the corrosive behaviour of lithium in stainless steel, an analysis method is required, which gives concentrations of lithium as well as the heavier constituents of the attacked steel with a positional resolution in the micrometer range. In the Karlsruhe ion microprobe the combination of the ⁷Li(p, α) reaction with PIXE (for heavier elements) and with RBS (for carbon and oxygen) covers all interesting elements. With 3 MeV proton impact energy, which is just above the broad reaction cross-section maximum, the alpha particle count rate is optimized. The horizontal and vertical sweeping of the proton microbeam ( ⋍ 2.5 μm diameter) across the specimen together with the energy loss of the alpha particles on their way through the specimen to the detector reveals a three-dimensional lithium concentration distribution in the micrometer range. In the investigated samples of stainless steel the positional correlation of lithium with oxygen and chromium indicates the formation of lithium chromate complexes at the expense of the chromium content in the neighbouring zone.     

Astrophysical S-factor for ~8B(p, γ)~9C via a Study of the ~8Li(d, p)~9Li Reaction

The 8B(p, γ)9C reaction plays a key role in the 7Be(p, γ)8B(p, γ)9C(α, p)12N chain which is believed to be a breakout path into the hot CNO cycles. 8B(p, γ)9C might be of importance for the evolution of massive stars with very low metallicities where     

Indirect Measurement of Cross Section of ~9Be(p,α)~6Li

The cross section of 9Be(p,α)6Li at low energies is important for nuclear astrophysics. But it is difficult for direct measurement because of the Coulomb barrier and electron screening effect. In order to measure the 9Be(p,α)6Li bare nucleus cross secti…     

Measurement of absolute reaction rates in Be,Pb and Fe spherical systems

The absolute reaction rates in Be,Pb and Fe have been measured by using the activation foil technique with different reaction energy thresholds.Thicknesses of Be,Pb and Fe spheres were 5.3,19.1 and 31.9cm.respectively,Eight kinds of activation folis were used for Fe,and four kinds each for Be and Pb,The total experimental er5ror was about 5-7%.The measured results were compared to the values calculated with the 1-D ANISN code and the ENDF/B-VI library data.The average ratio of the experimental to the calculational is less than 7% for Be and Pb,about 5-30% for Fe.     

Measurement of the 77Se(γ, n) cross section and uncertainty evaluation of the 79Se(n, γ) cross section

The ⁷⁷Se (γ, n) cross section was measured for the energy range from 7.6 to 13.8 MeV by using quasi-monochromatic laser-Compton scattering γ-rays. The advanced method to deduce γ-ray strength functions from (γ, n) cross section was developed. By utilizing the method, the γ-ray strength functions of ^{77, 78, 80}Se were deduced so as to reproduce the ^{77, 78, 80}Se (γ, n) cross sections measured in this work and previous systematic measurements. The inverse (n, γ) cross sections for ^{76, 77, 79}Se isotopes were calculated using the statistical model calculation code CCONE with the deduced γ-ray strength functions. The uncertainty of the calculated ⁷⁹Se(n, γ)⁸⁰Se cross section was evaluated by comparing the calculations and the experimental data on ^{76, 77}Se (n, γ) cross sections.     

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.     

Depth profiling of lithium by use of the nuclear reaction 7Li(p, α)4He

The nuclear reaction ⁷Li(p, α)⁴He induced by a primary beam of 1.5 MeV protons was used for measuring depth profiles of Li in Al. From the experiments with a detection angle of 90° a detection sensitivity of about 400 ppm was obtainable for a proton incidence at 30° from the surface. The best depth resolution was about 0.1 μm at 85° incidence. The sampling depth was over 17 μm at 50° incidence. These results are in good agreement with theoretical predictions. After the measurement of the reaction cross section, the applicability of the method to analyzing Li behaviour in solids was experimentally demonstrated on an AlLi (3.53 at.%) alloy.     

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.     

Reaction-yield dependence of the (γ, γ′) reaction of 238U on the target thickness

The dependence of the nuclear resonance fluorescence (NRF) yield on the target thickness was studied. To this end, an NRF experiment was performed on ²³⁸U using a laser Compton back-scattering (LCS) γ-ray beam at the High Intensity γ-ray Source facility at Duke University. Various thicknesses of depleted uranium targets were irradiated by an LCS γ-ray beam with an incident beam energy of ～2.475 MeV. The scattering NRF γ-rays were measured using an High-purity Germanium (HPGe) detector array positioned at scattering angles of 90° relative to the incident γ-beam. An analytical model for the NRF reaction yield (NRF RY model) is introduced to interpret the experimental data. Additionally, a Monte Carlo simulation using GEANT4 was performed to simulate the NRF interaction for a wide range of target thicknesses of the ²³⁸U. The measured NRF yield shows the saturation behavior. The results of both of the simulation and the analytical model can reproduce the saturation curve of the scattering NRF yield of ²³⁸U against the target thickness. In addition, we propose a method to deduce the precise integral cross section of the NRF reaction by fitting the NRF yield dependency on the target thickness without any absolute measurements.     

Measurement of thermal neutron cross-section and resonance integral for the Yb(n,γ)Yb reaction by the cadmium ratio method

The thermal-neutron cross-section and the resonance integral for the ¹⁷⁴Yb(n,γ)¹⁷⁵Yb reaction were measured by the activation method using a ⁵⁵Mn monitor as single comparator. Analytical grade MnO₂ and Yb₂O₃ powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three ²⁴¹Am-Be neutron sources. The gamma-ray spectra from the activated samples were measured with a calibrated n-type high-purity Ge detector. The experimental results were corrected for the correction factors calculated for thermal and epithermal neutron self-shielding effects, epithermal neutron spectrum shape and gamma-ray self attenuation. Thus, the thermal neutron cross-section for the ¹⁷⁴Yb(n,γ)¹⁷⁵Yb reaction is found to be 126.5 ± 6.6 b, relative to that of the ⁵⁵Mn monitor. The resonance integral value for the ¹⁷⁴Yb(n,γ)¹⁷⁵Yb reaction is found to be 59.6 ± 8.5 b, at cadmium cut-off energy of a 0.55 eV. Using the measured cadmium ratios of ⁵⁵Mn and ¹⁷⁴Yb, the result for resonance integral of the ¹⁷⁴Yb(n,γ)¹⁷⁵Yb reaction has also been obtained relative to the reference value of the ⁵⁵Mn monitor. The present results for the ¹⁷⁴Yb(n,γ)¹⁷⁵Yb reaction agree well only with the recent experimental ones obtained by Kafala et al. [1] and De Corte and Simonits [2] within uncertainty limits. However, the previously reported experimental data for the thermal neutron cross-section for this reaction are distributed between 24 and 141 b, and similarly the experimental values for the resonance integral value also show a large scatter in the range of 30-69 b.     

Measurement of Cross Sections for the Reaction ~(27)Al(n,p),~(56)Fe(n,p)and ~(64)Zn(n,2n)of 14.6MeV Neutrons and Simultaneous Evaluation of Some Cross Sections

1.Measurements The experiments were performed on 400 kV Cockcroft-Walton acceleratorof Nanjing University,using the T(d,n)~4He reaction to produce 14.6MeVneutrons.The energy of the incident deuterons was 200keV,the deuteroncurrent was 40μA,and the neutron yield was about 2×10~8 n/s.The ZnS neu-tron detector was used as flux monitor.Each sample to be measured was packedtogether in two standard sample foils of the same dimensions(2×1cm~2 rectang-lar foils and purities better than 99.5%)to form a sandwich so that they areirradiated in the same geometry.The γ-ray activities of the irradiated samplesand monitor foils were measured with a GEM-25210 type HPGe γ-spectrometer.The efficiency of this detector was determined with a ~(152)Eu standard γ source.