The 10B(n, αγ)7Li cross-section between 0.1 and 2.2 MeV

The shape of the excitation function for the standard neutron reaction ¹⁰B(n, αγ)⁷Li in the energy range from 0.1 to 2.2 MeV has been determined relative to the angular distribution of the neutron source reaction T(p, n)³He at 1.6, 2.3, and 3.0 MeV proton energy. The 478 keV γ's produced in a 3-mm thick boron carbide sample were observed in a Ge(Li)-detector. The time-of-flight method was used to discriminate against events from neutrons of degraded energy.     

Investigation of excited states of 7Li by means of thermal neutron capture

Capture of unpolarized thermal neutrons has been used to gain information on the ⁷Li level scheme. Two reactions have been investigated. Firstly, a study has been made of the decay scheme of ⁷Li through the ⁶Li(n, γ)⁷Li reaction. Three γ-transitions were observed and placed. The binding energy value of this reaction turned out to be Q = 7251.02(9) keV. Secondly, investigation of radiation from excited Li produced by the ¹⁰B(n,α)⁷Li reaction, made it possible to deduce a more precise lifetime of the 478 keV level of ⁷Li; namely τ = 102 ± 5 fs. This value is compared with existing data; it agrees with previous less accurate independent values and an average could be made in order to reduce the error further. As a byproduct the analysis of the peak shape of the 478 keV transition offered a new method for estimating the size of boron grains embedded in other materials.     

Bulk-compositional changes of Ni2Al3 and NiAl3 during ion etching

Bulk-compositional changes of Ni₂Al₃ and NiAl₃ in a Ni-50 wt% Al alloy during ion etching have been investigated by transmission electron microscopy and energy dispersive X-ray spectroscopic analyses. After etching with 7, 5 and 3 keV Ar⁺ ions for 15, 24 and 100 h nickel contents in both Ni₂Al₃ and NiAl₃ exceeded greatly those in the initial compounds and increased with the decrement of the sputtering energy. After 100 h etching with 3 keV Ar⁺ ions the compositions of these two compounds reached a similar value, about Ni_80-83Al_12-15Fe_3-4Cr_1-2 (at%). A synergistic action of preferential sputtering, radiation-induced segregation and radiation-enhanced diffusion enables the altered-layers at the top and bottom of the film extend through the whole film. The bulk-compositional changes are proposed to occur in the unsteady-state sputtering regime of ion etching and caused by an insufficient supply of matter in a thin film.     

替代241Am低能光子源的准单色X射线机的研制

研究了用滤光片法产生50～60 keV的准单色X射线的条件,对输出的X射线进行了数种金属滤光片实验研究,选出合适的滤光片,通过实验对准直器的机械结构进行了确定。采用自行设计委托加工的X射线管、准直器和购买的高压电源,组装成符合实验要求的X射机。该装置输出了50～60 keV能量段的准单色光谱,在料位计上能替代²⁴¹Am低能光子源。     

Neutron production cross sections and energies for the reactions 7Li(p,n)7Be and 7Li(p,n)7Be1

Center-of-mass best values for the normalized Legendre coefficients and the 0° differential cross sections as functions of input energy have been derived from various experimental results for the reactions ⁷Li(p,n)⁷Be and ${}^7\text{Li}\text{(p,n)}{}^7\text{Be}{}^1$ (431 keV). This information has been used to calculate laboratory differential cross sections as functions of the laboratory proton energy and neutron emission angle which are given in tabular form together with the corresponding neutron energies.     

Cross section measurements of the 23Na(n, 2n)22Na, 58Ni(n, 2n)57Ni and 115In(n,n′)115mIn reactions

Cross sections for two high energy threshold reactions ²³Na(n, 2n)²²Na and ⁵⁸Ni(n, 2n)⁵⁷Ni were measured by the activation method in the neutron energy range from 14 to 18 MeV. Inelastic scattering cross section for ¹¹⁵In was measured in the threshold region, i.e. from 0.5 to 1.3 MeV. The results of measurements are compared with scarce and divergent earlier data.     

Cross sections for K-shell ionization by 1H, 2H, 3He,and 4He ion impact

Cross section for K-shell ionization derived from experimental measurements with the light ions ¹H, ²H, ³He, and ⁴He are tabulated according to projectile energy and target atomic number.     

K-shell X-ray cross-section ratios for 1H, 4He and 6Li projectiles on targets from fluorine to titanium

Experimental K X-ray emission ratios have been measured for nine elements ranging from F to Ti (9 ? Z₂ ? 22) using ¹H⁺, and ⁶Li⁺ projectiles. The experimental ratios are in fair agreement with theoretical predictions for the velocity range studied, $\text{?}{}_{\mathrm{k}}\text{\$}\text{?}\text{1}$.     

Stopping cross sections and backscattering factors for 4He ions in matter Z = 1–92, E(4He) = 400–4000 keV

A table is presented of semiempirical values of stopping cross sections [expressed in eV/(atom/cm²)] for ⁴He ions in every element (1 ≤ Z ≤ 92) for ion energies from 400 to 4000 keV. The semiempirical results have been fitted with polynomial expansions whose coefficients are also tabulated. The stopping cross sections provide parameters for the interpretation of backscattering experiments, for example factors for converting backscattering-peak widths to areal density (atoms/cm²). The semiempirical results are based on recent experimental measurements and on theoretical values calculated in the Lindhard-Winther formalism with Hartree-Fock-Slater elemental wavefunctions. Comments are included on combining the specific energy loss tables for compound backscattering analysis by using Bragg's Rule, and also on the effects on backscattering of target tilt and of the finite thicknesses of targets.     

Ar-ion-milling-induced structural changes of Cu50Zr45Ti5 metallic glass

We have systematically studied Ar-ion-milling-induced microstructural evolution in Cu₅₀Zr₄₅Ti₅ metallic glass (MG) during specimen preparation for transmission electron microscopy (TEM). We have observed the formation of a Cu₁₀Zr₇ intermetallic phase in samples prepared using low energy ion milling (2 keV) but without evident crystallization. We also observed the formation of nanocrystalline Cu₁₀Zr₇ phase (with a possibility of being mixed with other minor phases) in samples prepared using high energy ion milling (?3 keV). In contrast, the MG samples remained in the glassy state without any microstructural changes when prepared by either electropolishing or low energy ion milling with liquid nitrogen cooling (2 keV). Further, our study suggests that chemical decomposition might be a necessary intermediate stage for crystallization. In situ TEM electron irradiation shows ion-milling-induced phase segregation and preferred nanocrystallization in the precipitated regions.     

α能谱法测量222Rn/220Rn气体活度浓度过程中的拖尾修正

α能谱法是环境中²²²Rn/²²⁰Rn气体活度浓度测量的重要方法之一。吸收层及探测器能窗等导致的α能谱低能拖尾是影响²²²Rn/²²⁰Rn活度浓度准确测量的重要因素。为修正α能谱法对²²²Rn/²²⁰Rn气体活度浓度的测量结果,本文从原理上探讨了拖尾形成的原因及其对²²²Rn/²²⁰Rn气体活度浓度测量的影响。结合商用测氡仪,实验修正了²²²Rn/²²⁰Rn气体活度浓度的测量结果,对修正前后的结果进行了实验比对。研究表明,经准确刻度后的修正因子和刻度因子能很好地用于修正²²²Rn/²²⁰Rn气体活度浓度的测量结果,保证了测量结果的准确性。建议在对α能谱法测量²²²Rn/²²⁰Rn气体活度浓度的仪器进行刻度检定时,必要情况下需对拖尾修正因子和刻度因子进行适当刻度。     

On the investigation of alpha-particle resonance elastic scattering from the 16O nucleus

Solid target measurements are conducted in order to investigate ¹⁶O(α, α₀)¹⁶O resonances in the energy region 2.0–3.6 MeV. Excitation functions are reported for scattering angles of 145° (θ_cm = 153°) and 165° (θ_cm = 168°), and resonances are observed at 2.522, 3.042, 3.082 and 3.372 MeV. The deduced widths of these resonances in the centre-of-mass frame are 19.00, 8.20, 3.36, and 15.10 keV respectively. It is reported that the widths of the first three resonances are in agreement with previous data, but the width of the 3.372 MeV resonance exceeds an early gas target result due to Cameron [5]. In addition, elastic scattering cross sections are compared with the gas target data and found to be consistent. It is concluded that the width of the 3^? resonance at 3.042 MeV is in agreement with the prediction due to multiparticle cluster calculations for ²⁰Ne.     

Depth distribution of rare earth ions implanted into KTiOPO4 determined by the Rutherford backscattering technique

Potassium titanyl phosphates (KTiOPO₄ or KTP) samples were implanted with rare earth ions such as Tm⁺, Er⁺, and Yb⁺. The ion energy implanted was varied from 100 keV up to 400 keV. The fluence was 1–2 × 10¹⁵ ions/cm². The depth distributions of the implanted rare earth ions were determined using the Rutherford backscattering technique. The experimental data were compared with TRIM (transport of ions in matter) code. It is found that for Tm⁺ and Er⁺ the experimental mean projected ranges are in relatively good agreement with values calculated by the TRIM code after taking into account inelastic effects in the energy transfer. But that in the case of Yb⁺ the ranges are overestimated by theory, anyway the deviation of experimental values from calculated one is less than 9% for all cases. The deconvoluted experimental range stragglings are in all cases higher than the calculated values.     

Measurement of the 239Pu(n,f) cross section from thermal up to 30 keV neutron energy

At GELINA measurements of the ²³⁹Pu fission cross-section were performed covering the neutron energy region from thermal up to 30 keV. Fission fragment as well as fission neutron detection techniques were used. Also for the neutron flux determination different methods were applied. From the σ_f-data, several fission integrals were calculated and compared with other results.     

Double electron capture by protons in collisions with H2

Double electron capture of protons in collisions with molecular hydrogen in the energy range 1.5-10 keV was studied by measuring the resulting H^- velocity distributions. In this paper, a technique that provides experimental evidence about double capture mechanisms is proposed. In addition, cross-sections for this process were measured in the energy range of 1-5 keV.     

Effect of the laser focus position on characteristics of X-ray and ion emission from gold plasmas generated by a sub-nanosecond laser

X-ray and ion emission from gold plasma produced by a sub-nanosecond Nd:glass laser has been studies as a function of distance of the target from the best focus position. Thermal ion (kinetic energy <19 keV) signals and soft X-ray flux (photon energy >0.7 keV) measurements decrease as the target is moved closer to the best focus position in spite of an increase in laser intensity. We observe simultaneously a strong correlation between the onset of this drop in the flux of soft X-ray and the growth of harder X-ray (photon energy 3–5 keV), alongside a growth in fast ion (energy >67 keV) numbers. This is indicative of the onset of non-linear processes at the higher irradiances (～10¹⁴ W/cm²) associated with the best focus position. Our results show that when using laser plasmas as X-ray or ion sources, X-ray and ion emission in a desired spectral range can be optimized by adjusting the focusing on the target.     

Dissolution of precipitates in Al-Ge during 200 keV Al + ion irradiation

The effect of recoil dissolution on precipitate stability during irradiation has been studied in an Al-Ge alloy. Two-phase samples of Ge precipitates in an Al matrix have been irradiated at ? 100°C with 200 keV Al⁺ ions to doses between 6 and 122 dpa. Transmission electron microscopy observations have shown that individual precipitates are replaced by families of precipitates as a result of low-temperature irradiation and warming to room temperature. The microstructure at room temperature following low-temperature irradiation is thought to be determined by the amount of cascade mixing of solute atoms and solvent atoms during irradiation and the degree of re-nucleation in the solute-enriched region surrounding the original precipitate site during warming to room temperature.     

Design of the thermal neutron beam for neutron radiography at the Syrian MNSR

Neutron beam design was studied at the Syrian reactor (MNSR, 30 kW) with a view to generating thermal neutron beam in the vertical irradiation sites for neutron radiography. The design of the neutron collimator was performed using MCNP4C and the ENDF/B-V cross-section library. Thermal, epithermal and fast neutron energy ranges were selected as <0.4 eV, 0.4 eV–10 keV, >10 keV, respectively. To produce a good neutron beam quality, bismuth was used as photon filter. In this design, the L/D ratio of this facility had the value of 125. The thermal neutron flux at the beam exit was about 2.548 × 10⁵ n/cm² s. If such neutron beam were built into the Syrian MNSR many scientific applications would be available using the neutron radiography.     

Hydrogen backscattering from TiN,TiC and TiB2

Particle reflection coefficients, R_n, for H⁺ and H₂⁺ bombarding TiN, TiC and TiB₂ targets were determined by measurement of the energy distributions of neutral and charged particles backscattered at 135°. The values of R_n were determined for incident energies between 2.5 and 10 keV and were found to decrease with increasing energy. The reflected fractions were also found to decrease in going from TiN to TiC to TiB₂ at any given incident energy. The angular distribution of particles backscattered from TiC bombarded by 10 keV H₂⁺ was measured and found to agree well with a cosine distribution.     

Range distributions of 50–400 keV Hg+in amorphous silicon and Si-Ar binary targets

Range distributions of 50–400 keV Hg⁺ in amorphous Si and Si-Ar binary targets have been investigated by Rutherford backscattering spectrometry. The Si(100) wafers were amorphized by means of 150 keV Ar⁺ irradiation to a dose of 2 × 10¹⁵ ions/cm². To produce Si-Ar binary targets, the Si(100) wafers were implanted with 150 keV Ar⁺ to a dose of 3 × 10¹⁷ ions/cm². 50–400 keV Hg⁺ were introduced into amorphous Si and Si-Ar binary targets in increments of 50 keV. Parallel scanning of the Hg⁺ beams was used. The measured ranges and range stragglings have been compared to the Biersack theory. The results show that good agreements are found between the experimental and theoretical projected ranges for both Si and Si-Ar, but the predicted range straggling for both Si and Si-Ar are systematically lower than the experimental results in the case of a first order treatment. After correcting for second order energy loss terms, a better agreement for the range straggling is obtained.