共查询到20条相似文献,搜索用时 125 毫秒
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高效率的正电子湮没2γ和3γ寿命谱仪 总被引:1,自引:0,他引:1
用大体积BaF2 (φ40mm×30mm)探测器组装正电子湮没的2γ和3γ寿命谱仪,在2γ方式下,两个BaF2探测器构成双重符合,得到系统的时间分辨为FWHM=212ps,计数效率比塑料闪烁探测器组装的谱仪估计高10倍以上.在3γ方式下,NaI(Tl)探测器与两个BaF2构成三重符合,合理安排三探头的几何及合理选择各能窗的位置以优化对3γ湮没事例的测量,实验表明,新系统可用于研究强度微弱的电子偶素在固体中湮没的3γ寿命谱. 相似文献
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BGO高能γ探测器性能测定与效率模拟 总被引:1,自引:0,他引:1
实验测定了两套新制作的φ75×100 BGO高能γ探测器的能量分辨与时间分辨,根据BGO晶体中Ge的热中子俘获所释放的2条高能γ射线对γ能谱作能量刻度.模拟计算了4—30MeV能量区间BGOγ探测器的全能峰效率、单逃逸率与双逃逸率,计算了入射γ光子在0—30MeV区间均匀分布时BGO探测器的实际计数响应与计数效率随γ光子能量的变化,分析了γ光子在探测介质中的能损向下延展造成的能谱扭曲. 相似文献
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To improve the via fill capability of electroless (EL) Cu, we explored the influence of the Pd activation process prior to EL Cu deposition. We found that EL Cu roughness is closely related to the Pd nuclei size range and density, which are functions of Pd activation time. With activation time, Pd deposition goes through the sequential stages of growth, secondary nucleation, and ripening. The smoothest EL Cu film can be achieved with a Pd nucleation time that corresponds to the beginning of the ripening stage. A Pd activation process that leads to the smoothest EL Cu deposit also yields the most conformal via filling. 相似文献
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采用基于密度泛函理论的第一性原理,研究了稀土La对bcc-Fe中Cu析出行为的影响.计算了α-Fe中La原子和Cu原子与空位之间,以及La原子和Cu原子之间的点缺陷结合能;在此基础上,讨论了α-Fe中La对Cu扩散激活能的关系.结果表明:La原子与空位之间有较强的相互吸引作用,且对近邻Cu原子也有一定的束缚.此外,La的加入使Cu原子近邻的空位形成能显著升高,这表明La,Cu偏聚区形成空位较为困难.与此同时,由于La原子对近邻空位和Cu原子的吸引作用,使Cu原子向近邻空位跳跃的迁移能有所升高.迁移能与空位形成能变化的计算结果显示,La原子的加入能够使α-Fe中Cu的扩散激活能显著升高,从而延缓了铁素体区富铜相的偏聚和析出. 相似文献
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介绍了铜活化诊断氘氚中子产额的测量原理,分析了62 Cu和64 Cu两种活化核素在符合测量中的贡献。针对不同范围内的中子产额测量,提出了系统灵敏度相对标定法和64 Cu活化核标定法。通过添加中子屏蔽锥测量了标定场所散射中子影响。计算评估了63 Cu(n,γ)64 Cu反应过程对活化测量的影响。在神光Ⅲ主机装置上,利用该系统测量了直接驱动氘氚中子产额。实验结果表明:氘氚中子产额在109~1013范围采用相对标定方法较为合适,64 Cu活化核的标定方法适用于1012~1016范围内产额测量。标定场所散射中子对灵敏度标定因子影响约0.4%。63 Cu俘获辐射反应在64 Cu活化核标定中贡献小于1%。目前神光Ⅲ主机装置直接驱动氘氚中子产额约8×1012。 相似文献
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本文提出了衍射分析用的X射线管谱线纯度的定量测定方法。在国产衍射仪上用石英单晶作分光晶体进行展谱测定。实验测得的各种波长X射线的强度应还原为X射线管窗口处的出射强度。对影响强度的各种因素作了详细的理论分析,给出了对应于不同靶、不同杂质元素的强度还原换算因子表。X射线管阳极靶元素主特征谱线强度用铜或铝吸收箔进行衰减,以避免计数损失造成的误差。用这一方法,对许多X射线管进行了测定。
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The present paper is aimed mainly to investigate theoretically the diffusion of Ag, Cu, Au and Pt adatoms on the (1 × 1) unreconstructed geometry for Ag, Cu and Pt (110), and reconstructed geometries ((1 × 2), (1 × 3) and (1 × 4)) for Pt and Au (110) surfaces. We consider the single adatom diffusion when additional atoms are deposited in adjacent row. For this study, we have used the molecular statics simulations combined with the embedded atom method. For several systems, we have calculated the activation barriers for hopping mechanism. For the diffusion on the unreconstructed surfaces, the trends for the activation barriers are the same for all considered systems except for Cu/Ag (110) system, where the activation barrier do not change. Further, our results indicate that additional atoms lead to a small decreasing of activation barriers for diffusion on reconstructed surfaces for some systems, while for other systems; the activation barrier remains practically unchanged. 相似文献
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Masaki Tanaka Daichi Izumi Nobuyuki Yoshimura Genichi Shigesato Manabu Hoshino Kohsaku Ushioda 《哲学杂志》2013,93(31):2915-2930
AbstractThe temperature dependence of the yield stress, effective stress and activation volume on the Cu content in steel was assessed using polycrystalline ultra-low carbon steels with 0.5, 1 and 2 mass% Cu added. A small hump was seen in the effective stress–temperature curve for ultra-low carbon steel, which has also been reported for high-purity single-crystal iron. The effective stress was found to decrease with increasing the Cu content. The activation volume was found to be linearly related to the temperature at low temperatures for all types of specimens considered. The activation volume was found to increase abruptly at a certain temperature, which increased with increasing the Cu content. The change in the relationship of the activation volume to temperature is discussed in this paper with respect to the thermally activated process of dislocation glide from the Peierls mechanism to the interaction between dislocations and solute Cu atoms. 相似文献
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Grain boundary (GB) motion in high-purity Cu material (5N8 and 5N Cu) is investigated using the results of radiotracer GB diffusion measurements with tracers exhibiting fundamental differences in the solute-matrix atom interactions. The results on GB solute diffusion of Ag (revealing a miscibility gap in the Ag-Cu phase diagram) and Au (forming intermetallic compounds with Cu) in Cu and on Cu self-diffusion are analyzed.The initial parts of the Ag and Cu penetration profiles turned out to be substantially curved. The profile curvature is explained via the effect of GB motion during 110m
Ag and 64Cu GB penetration. The activation enthalpies of GB motion in these two independent measurements occurred to be very close, 95 and 103 kJ/mol, respectively. Moreover, these values turn out to be close, but still somewhat larger than the activation enthalpy of Cu GB self-diffusion in Cu material of the same very high purity, Q
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gb = 72 kJ/mol. Although tracer diffusion measurements of Au GB diffusion in Cu yielded only limited information on GB motion, the absolute values of GB velocities are consistent with those calculated from the Ag and Cu GB diffusion data. 相似文献
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Triton-emission cross sections were measured for Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ag, Ta, Tl, Pb and Bi with a 30 MeV d(Be) break-up neutron spectrum characterized by a multiple-foil activation technique. The accumulated tritium was separated by vacuum extraction and measured by low-level gas-phase β? counting. The systematic trend in the cross sections is somewhat similar to that in the 53 MeV d(Be) break-up neutron spectrum; apart from some initial decrease as a function of Z, the cross section is almost constant over the entire range of Z = 22 to 83. The magnitudes of the cross sections lie between those with 14 MeV neutrons and 53 MeV d(Be) break-up neutrons. Hauser-Feshbach calculations show that the statistical model describes the triton-emission cross sections for nuclei in the (2s, ld) shell within a factor of 2; for the heavier nuclei, however, the calculated cross sections are much smaller than the experimental values. 相似文献
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液态固体电解质材料的离子电导率低,安全性问题在一定程度上限制了其发展与应用,而固体电解质材料在室温下具有很好的稳定性和高的离子电导率值,具有较好的应用前景.本文采用机械化学球磨法制备固体电解质Rb4Cu16I7Cl13粉末,探索制备工艺和球磨参数,对其晶体结构进行解析、观察粉体微观结构、通过交流阻抗谱及等效电路分析得到了离子电导率与活化能、并详细探讨其离子传导性能与晶体结构的关系以及化学成分稳定性进行研究.实验结果表明,在480 rpm转速下球磨6 h时可得到纯的固体电解质Rb4Cu16I7Cl13物相.粉体晶粒尺寸分布均匀,均在20 nm-400 nm之间,室温下固体电解质Rb4Cu16I7Cl13离子电导率可达到0.213 S/cm且活化能为0.087(9)eV.在真空干燥条件下存放5天和12天后观察了微观形貌和化学稳定性... 相似文献