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41.
慢速中子俘获过程(s过程)是合成比铁重元素的重要途径之一。22Ne(α,n)25Mg反应是大质量AGB星中s过程主要的中子源,其中的22Ne主要通过14N(α,γ)18F(β+)18O(α,γ)22Ne反应链合成。该反应链中关键反应18O(α,γ)22Ne在天体物理感兴趣能区的截面非常低,其天体反应率主要来自于22Ne α分离阈附近低能共振态的贡献,但目前相关能级的共振参数严重缺失。在HI-13串列加速器的Q3D磁谱仪上,通过测量18O(6Li,d)22Ne反应的角分布,利用DWBA分析确定了22Ne分离阈附近共振能级Eα=470 keV的自旋宇称为0+,为后续计算18O(α,γ)22Ne的天体反应率打下了基础。About a half of the abundances of elements heavier than iron comes from the so-called slowneutron capture process (s-process) in Asymptotic Giant Branch (AGB) stars, with the 22Ne(α, n)25Mg reaction as one of the main neutron sources. In the beginning phase of AGB thermal pulse, 22Ne is produced by the 14N(α, γ)18F(β+)18O(α, γ)22Ne reaction sequence, in which the 18O(α, γ)22Ne reaction plays a key role. While the reaction rate of the 18O(α, γ)22Ne is mainly affected by several resonant states lying closely to the α threshold in 22Ne, up to now, the relevant 22Ne parameters are fragmentary in the energy region corresponding to the typical temperatures of s-process. The direct measurement of the 18O(α, γ)22Ne reaction rate is extremely difficult due to the very low cross section. In this work, we investigated the 22Ne resonant states via the 18O(6Li, d)22Ne reaction at the Beijing HI-13 tandem accelerator of China Institute of Atomic Energy. Based on the DWBA analysis, preliminary results showed that the spin-parity of 22Ne Eα=470 keV resonant states was assigned as 0+, which would make contributions to subsequent calculation for the reaction rate of the 18O(α, γ)22Ne. 相似文献
42.
韩建龙 王琦 白真 董玉川 李松林 段利敏 徐瑚珊 徐华根 陈若富 吴和宇 李志常 路秀琴 赵葵 周平 刘建成 许国基 Sergey Yu Kun 《原子核物理评论》2008,25(4):322-326
在中国原子能科学研究院的HI 13串列静电加速器上完成了19F+27Al耗散反应产物的激发函数测量。 束流19F的入射能量从110.25 MeV到118.75 MeV, 步长250 keV, 测量了实验室系+57°, +31°, -15°和-29°出射的类弹产物B, C, N, O, F和Ne的激发函数。 观测到激发函数具有耗散反应的特征涨落结构, 分析了激发函数之间的长程角度关联以及强烈的电荷数关联。 Excitation functions have been measured for the projectile like fragments of B, C, N, O, F and Ne in the 27Al(19F,x)y reactions at incident energies from 110.25 MeV to 118.75 MeV in 250 keV steps. Strong cross section fluctuations in the excitation functions has been observed. The cross correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle θ cm have been deduced. These coefficients are much larger than the statistical theoretical calculated ones. This indicates that there are strong correlations between different exit channels in the dissipative heavy ion collision of 27Al(19F, x)y. 相似文献
43.
Statistical Significance of Non-Reproducibility of Cross Sections in Dissipative Reactions 下载免费PDF全文
Two independent excitation function measurements have been performed in the reaction system of ^19F ^93Nb using two target foils of the same nominal thickness. We measured the dissipative reaction products at incident energies of 102 through 108 MeV with a step of 250ke V. The variance of energy autocorrelation functions of the reaction products was found to be three times of that originated from the randomized counting rates. By analysing the probability distributions of the deviations in the measured cross sections, we found that about 20% of all the deviations exceeds three standard deviations. This indicates that the non-reproduclbility of the cross sections in the two independent measurements is of a statistical significance but not originated from randomized fluctuation of counting rates. 相似文献
44.
现代大型常规电站汽轮机所用的工质--高温高压过热蒸汽--在汽轮机通道中膨胀作功进入低压部分时,蒸汽中凝结出水滴,成为汽相和液相的两相介质,即所谓湿蒸汽。湿蒸汽中水滴的出现,一方面会引起动量 ... 相似文献
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Angular dependence of proton-induced single event transient in silicon-germanium heterojunction bipolar transistors 下载免费PDF全文
Jianan Wei 《中国物理 B》2022,31(8):86106-086106
We investigate the angular dependence of proton-induced single event transient (SET) in silicon-germanium heterojunction bipolar transistors. Experimental results show that the overall SET cross section is almost independent of proton incident angle. However, the proportion of SET events with long duration and high integral charge collection grows significantly with the increasing angle. Monte Carlo simulations demonstrate that the integral cross section of proton incident events with high ionizing energy deposition in the sensitive volume tends to be higher at larger incident angles, which is associated with the angular distribution of proton-induced secondary particles and the geometry of sensitive volume. 相似文献
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de Sitter空间中具有常数量曲率的完备类空子流形的间隙现象 总被引:1,自引:0,他引:1
设Mn是de Sitter空间Snp p(c)中具有常数量曲率R(≤c)的完备类空子流形.得到了Mn关于其第二基本形式模长平方‖h‖2的间隙性定理,如果n(c-R)≤‖h‖2≤2√n-1c,那么,或者‖h‖2=n(c-R)且Mn是全脐点子流形,或者‖h‖2=2√n-1c且Mn是全脐的或是双曲柱面Sn-1(c-tanh2r)×H1(c-coth2r). 相似文献
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50.
对于盐熔法合成的LiNdP4O12单晶进行了X射线衍射分析,该晶体属于单斜晶系,空间群为C2/c,z=4,晶胞参数为:α=16.486?,b=7.073?,c=9.775?,β=126.23°,全矩阵最小二乘法修正给出1251个独立反射的R=0.054,Rω=0.050,经吸收和次级消光校正后,R=0.048,Rω=0.043,基本的结构单位是(PO3)n的螺旋带,它们由共角
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