Resonance scattering of γ-rays in Mg24

Resonance scattering of -rays With energies E₁=1.38 Mev, corresponding to the transition to the ground state in Mg²⁴. have been observed in metallic magnesium. The energy given off by the -ray (E₁=1.38 Mev) in emission and collision with the nucleus, is compensated for by the energy obtained due to recoil associated with the emission of the preceding -ray with an energy E₂ = 2.76 Mev. Using a fast coincidence method and amplitude discrimination, coincidences were recorded between the -rays with energies E₁=1.38 Mev and E₂=2.76 Mev. Scattercrs of magnesium and aluminum were alternately placed in the path of the 1.38 Mev -rays. The source was radioactive Na²⁴ in a water solution of NaOH. At an angle of 120 ° between the -rays a strong attenuatlon of the 1.38 Mev -rays was observed; this is attributed to resonance scattering. When the angle between the -rays was varied by 5 °. the strong attenuation of the flux disappeared. The width of the level at 1.38 Mev in Mg²⁴ has been estimated at > 1.6· in^–4 Mev.     

0.70～2.48 MeV质子在F和Mg上160°背散射截面测量

应用北京师范大学2×1.7MV串列静电加速器提供的质子束,采用相对测量方法测量了0.70～2.48MeV宽能区质子在轻核F和Mg上160°（实验室坐标系）背散射截面。测量得到F、Mg各自对应能区的质子共振背散射截面数据,为含F、Mg轻元素的新型薄膜材料的高灵敏分析提供了实验数据。     

Determination of Astrophysical ^26Si（p, γ）^27p Reaction Rate From Asymptotic Normalization Coefficients of ^27Mg →^26Mg ＋ n

The 1.809 MeV T-ray from the decay of ^26Al is an excellent observable for some astrophysical events, such as novae and X-ray burst. The nucleosynthesis of ^26A1 is dominated by the reaction chain ^24Mg（p,γ）^25Al（β＋）^25Mg（p,γ）^26Al, however,     

Investigation of Orbits and Stability of Negative Ions of Hydrogen (H<Superscript>−</Superscript>) in Simulated Main Magnetic Field of AVF Cyclotrons

This paper describes equilibrium orbit and stability of negative hydrogen ions (H⁻) on a four sector of tight design giving 30 MeV protons. We simulated radial and vertical changes of main magnetic field of Cyclone-30 by multi degree and Fourier functions. Based on measured main magnetic field by IBA (Ion Beam Application), we calculated coefficients of these functions and investigate equilibrium orbit and stability includes Betetatron frequency, radial and vertical motion and etc. Advanced graphical tools of MATLAB give good visualization features to created models. The simulation results are in good agreement with experimental data.     

同位素Mg靶的制备

文章介绍了＾２４ＭｇＯ转换成金属小球的还原技术以及同位素Ｍｇ的３种制备方法，即轧法，电阻加热法和聚焦重离子溅射法。滚轧法适用于制备〉０．１５ｍｇ／ｃｍ＾２的自支撑＾２４Ｍｇ靶，而后２种方法主要用来制作有衬底靶。     

Experimental stopping powers of Al,Mg, F and O ions in ZrO2 in the 0.1–0.6 MeV/u energy range

The study of the stopping and range of heavy ions (Z > 3) in matter isdsc cfddc of both fundamental and practical interest as heavy ions find increasing usage in a wide range of ion beam based techniques. While semi-empirical formulations like the widely used SRIM code can predict the stopping powers of hydrogen and helium in many elemental and compound targets over a wide range of energies quite well, their predictive accuracy for heavy ions is not as good. This is mainly due to the lack of heavy ion experimental stopping power data on which such codes are based. We present results of measurements performed using a Time of Flight–Energy spectrometer to determine the stopping powers of O, F, Mg and Al ions in the oxide ceramic ZrO₂ within the 0.1–0.6 MeV/u energy range. Possible SRIM correction (or correlation) factors for F, Mg and Al ions were extracted from quantitative comparisons of experimental and predicted stopping power values.     

β Decay Study of T_z=-2 Proton-rich Nucleus ~(20)Mg

正For explosive hydrogen burning environments such as classical novae and typeⅠX-ray bursts,our current understanding of nucleosynthesis and energy generation in these astrophysical scenarios is limited by the uncertainties in particular thermonuclear reaction rates.The     

Parameters of <Emphasis Type="Italic">s</Emphasis>-resonances in <Superscript>246–248</Superscript>Cm fission cross sections

The fission cross sections of ²⁴⁶Cm, ²⁴⁷Cm, and ²⁴⁸Cm isotopes measured with an SVZ-100 spectrometer, based on neutron moderation in lead, at the Institute of Nuclear Research of the Russian Academy of Sciences are analyzed. The area of the resolved resonances is calculated, and their neutron and fission widths are determined. The results are compared with existing data and recommended evaluations.     

Calculation of Cross-sections and Astrophysical S-Factors for <Superscript>62</Superscript>Ni(α,n) and <Superscript>62</Superscript>Ni(α,γ) Reactions of Structural Fusion Material Nickel

Nickel is an important element in fusion reactor technologies and astrophysical applications. Therefore, the knowledge of astrophysical S-factors and cross-sections on nickel isotopes is needed. In this work, the cross sections of the ⁶²Ni(α,n) and ⁶²Ni(α,γ) reactions have been calculated. The alpha capture cross sections was calculated up to 10 MeV. In these theoretical calculations, the TALYS 1.6 and NON-SMOKER codes were used. Also for the ⁶²Ni(α,n) and ⁶²Ni(α,γ) reactions, we calculated the astrophysical S-factors that determine the probability of reaction in low energies. Results of our calculations were checked to the experimental data obtained from EXFOR database.     

高功率Mg反应靶的研制

<正>在未来锦屏深地核天体物理实验研究中,所测量的天体核反应在伽莫夫能量窗口内的截面极低。只能依靠强地下较低的本底水平,并配合使用强流加速器和高效率的探测器才能完成对这些反应的直接测量。而在强束流实验中,反应靶的辐射损伤会造成材料和组分发生变化,会进一步影响实验测量的精度。因此,采取措施维持反应靶的稳定性是强流束实验中的关键。     

Determination of Astrophysical ~(26)Si(p, γ)~(27)P Reaction Rate From Asymptotic Normalization Coefficients of ~(27)Mg → ~(26)Mg n

The 1.809 MeV γ-ray from the decay of 26Al is an excellent observable for some astrophysical events, such as novae and X-ray burst. The nucleosynthesis of 26Al is dominated by the reaction chain 24Mg(p,γ)25Al(β )25Mg(p,γ)26Al, however, it is complicat…     

Calculations of Excitation Functions of Some Structural Fusion Materials for (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">t</Emphasis>) Reactions up to 50 MeV Energy

Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, the working out the systematics of (n, t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. In this study, (n, t) reactions for some structural fusion materials such as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn, and ⁵⁶Fe have been investigated. The new calculations on the excitation functions of ²⁷Al(n, t)²⁵Mg, ⁵¹V(n, t)⁴⁹Ti, ⁵²Cr(n, t)⁵⁰V, ⁵⁵Mn(n, t)⁵³Cr and ⁵⁶Fe(n, t)⁵⁴Mn reactions have been carried out up to 50 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model, hybrid model and the cascade exciton model. Equilibrium effects are calculated according to the Weisskopf–Ewing model. Also in the present work, we have calculated (n, t) reaction cross-sections by using new evaluated semi-empirical formulas developed by Tel et al. at 14–15 MeV energy. The calculated results are discussed and compared with the experimental data taken from the literature.     

自支撑Mg靶膜的制备

用真空蒸发法成功制备了１７０．０～１９６．１μｇ／ｃｍ＾２的薄自支撑Ｍｇ靶膜和９０～９５μｍ的厚自支撑Ｍｇ靶膜。甜菜碱是制备Ｍｇ靶膜有解离剂，讨论了真空蒸发制靶过程中的主要技术难点。     

Measurement of neutron capture cross-section of the Ga(n, γ)Ga reaction at 0.0536 eV energy

The neutron capture cross-section for the ⁷¹Ga(n,  γ)⁷²Ga reaction at 0.0536 eV energy was measured using activation technique based on TRIGA Mark-II research reactor. The ¹⁹⁷Au(n, γ)¹⁹⁸Au monitor reaction was used to determine the effective neutron flux. Neutron absorption and γ-ray attenuation in gallium oxide pellet were corrected in determination of cross-section. The cross-section for the above reaction at 0.0536 eV amounts to 2.75 ± 0.14 b. As far as we know there are no experimental data available at our investigated energy. So far we are the first, who carried out experiment with 0.0536 eV neutrons for cross-section measurement. The present result is larger than that of JENDL-3.3, but consistent within the uncertainty range. The value of ENDF/B-VII is higher than this work. The result of this work will be useful to observe energy dependence of neutron capture cross-sections.     

R&D on Agitator System of ф300mm CCM

正Agitating is a general operation in chemical industry,which can improve the mixing between the reagents and avoid side reaction occurring or organic material decomposition because of the heterogeneous of reagent concentration or uneven heating in the vessel.The stirrer can make the reagents concentration homogenous,even heated,and also shorten the reaction duration and     

Experimental determination of <Superscript>80,82,83</Superscript>Kr(α, <Emphasis Type="Italic">xn</Emphasis>)<Superscript>82</Superscript>Sr cross sections for reaction threshold to 60 MeV α-particles

The activation method has been used to determine the experimental cross sections of the nuclear reactions ⁸⁰Kr(α, 2n)⁸²Sr, ⁸²Kr(α, 4n)⁸²Sr, and ⁸³Kr(α, 5n)⁸²Sr for α-particle energies from the reaction threshold to E_α = 60 MeV on targets which are highly enriched with krypton isotopes. The structural and geometric parameters are established for a “thick” cascade target with krypton isotopes, which gives maximum ⁸²Sr yield for E_α ≤ 60 MeV. The ⁸²Sr yield in the indicated target for initial energy E_α = 60 MeV is estimated to be 3.4·10⁶ Bq/(μA·h), which gives a basis for commercial applications of this isotope in medium-energy accelerators.     

Comparison of Level Density Models for the <Superscript>60,61,62,64</Superscript>Ni(p,n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on ^60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for ^60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.     

Interaction of 〈1 0 0〉 and ½〈1 1 1〉 dislocation loops with point defects in ferritic alloys

The interaction between dislocation loops of interstitial nature with ½〈1 1 1〉 and 〈1 0 0〉 Burgers vectors and point defects in Fe has been studied molecular dynamics. Comparative calculations have been carried out using two interatomic potentials for pure Fe ([G.J. Ackland, M.I. Mendelev, D.J. Srolovitz, S. Han, A.V. Barashev, J. Phys.: Condens. Mater. 16 (2004) 1; S. Dudarev, P. Derlet, J. Phys.: Condens. Mater. 17 (2005) 7097]). The results of this study are range and energy of the interaction as functions of size and mutual position of defects. The applied potentials predict somewhat different strain field structure for 〈1 0 0〉 loops and therefore different lengths of interaction. However, both potentials suggest that, contrary to common belief, the distance of cluster-defect interaction within the glide prism of a ½〈1 1 1〉 cluster is significantly longer than that of a 〈1 0 0〉 cluster of similar size, in spite of the longer Burgers vector in the latter case.     

Effect of 1.25 MeV gamma irradiation in α-phased PVDF

The radiation induced changes taking place in α-phased poly(vinylidene fluoride) (PVDF) films exposed to gamma rays were investigated in correlation with the applied doses. Samples were irradiated in vacuum at room temperature by a 1.25 MeV Co⁶⁰ source with the doses in the range of 0–300 kGy. Optical and chemical properties of the irradiated as well as un-irradiated PVDF films were studied using UV–visible and FTIR techniques. Gamma irradiation was found to induce changes vary depending on the radiation dose.     

Determination of the neutron flux and <Emphasis Type="Italic">γ</Emphasis> radiation in the core of operating and shut-down reactors using quartz glasses and element monitors

The neutron fluxes and the intensity of γ radiation are measured in 26 channels of a VVR-SM reactor and its thermal column. The fast neutron fluxes in the channels are determined using Ni, Fe, Co, Au, and Mn element monitors with different threshold energies, together with a theoretical calculation using the MCNP-4C program. The energy distribution of the neutron flux inside the fuel assembly is obtained for selected channels around the core. The flux of neutrons with energies >1 MeV is in the range (0.5–43)·10¹² cm⁻²sec⁻¹, depending on the location of the channel. A linear correlation is discovered between the induced optical absorption at the 215 nm line (E′ center) of SiO₂–BaO glass and the fast neutron flux in the channels. The γ-ray intensity in the thermal channel is estimated for the reactor during operation (∼38.4 Gy/sec) and 24 hours after it is shut down (∼24.7 Gy/sec) using the E′ centers induced in pure quartz glasses. The observed difference in the efficiency with which oxygen defects are formed during dry and wet irradiation of glass owing to the radiolysis of water must be taken into account when developing radiation technology and during the burial of radioactive waste. Translated from Atomnaya énergiya, Vol. 105, No. 3, pp. 160–164, September, 2008.