Study of fusion Q-value rule in sub-barrier fusion of heavy ions

A vast body of fusion data has been analyzed for different projectiles and target nuclei. It is indicated that the sub-barrier fusion depends on the fusion Q-value. In terms of a recently introduced fusion Q-value rule and an energy scaling reduction procedure, the experimental fusion excitation functions are reduced and compared with each other. It is found that the reduced fusion excitations of selected fusion systems show a similar trend. The fusion data for massive nuclei are in agreement with the Q-value rule. In the fusion process, the Q contribution should be considered. Within this approach, the sub-barrier fusion cross sections of most fusion systems can be predicted without involving any structure effects of colliding nuclei. Instances of disagreement are presented in a few fusion systems. The use of the energy scaling as a criterion of possible experimental data inconsistency is discussed. More precise experimental fusion data need to be measured.     

蒙特卡罗方法计算铅玻璃探测器对高能γ射线探测效率

本文使用蒙特卡罗方法模拟了铅玻璃中发生的电磁簇射过程, 考虑了光收集效应, 给出了铅玻璃探测器对能量为8—300MeV入射γ射线的探测效率函数、能量分辨曲线及光电子数目分布(脉冲辐度谱)结果满意.     

用于测量熔合反应的静电偏转板介绍

An electrostatic deflector for separating the fusion evaporation residues from the beam-like products in heavy ion reactions was installed. The evaporation residue separation and identification with the electrostatic deflector setup was tested with the reaction ^32S＋^96Zr at several energies. The fusion evaporation residues and the beam-like particles were well separated after the electrical separation and the experimental fusion cross section obtained from the angular distribution is in good agreement with the calculated value well above the Coulomb barrier. This confirms the reliability of the setup.     

替代反应法测量锕系核(n,f)和(n,xn)截面

对于某些中子反应截面,在直接测量上存在困难。为了获得那些对核能发展极其重要的核数据,人们提出替代反应法,即利用带电粒子代替中子进行反应,从而实现中子反应截面间接测量的方法。现有替代反应一般采用非弹激发、转移等周边反应,涉及的角动量远比中子反应的大,需要理论修正,这造成了一定的困难。有鉴于此,提出利用轻带电离子的俘获反应作为替代反应,其复合核自旋与中子反应的相当,有效避免了自旋修正的困难。根据这个思路,采用236U的（α,f）和（α,2n）反应作为替代反应,成功提取了239Pu的（n,f）和（n,2n）反应截面,与ENDFB7评价库数据在误差范围内符合较好,表明了替代反应法的优越性,可以在核数据测量中推广应用。There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.     

引领我步入科学研究之门的何泽慧先生

1956年秋,我被分配到中国科学院物理研究所,有幸在钱三强、何泽慧先生领导的中子物理研究室工作,当时在戴传曾先生研究组里参加建立中子晶体谱仪的工作,并准备中子截面测量的知识。可一开始何先生就提醒我,除了准备中子截面测量外,还要及早学习中子衍射方面的知识,为中子晶体谱仪的进一步发展做准备,使我在组里较早地开始了这方面的学习。1958年9月何先生作为我们的室主任,通知我去苏联实习。我到了莫斯科库尔恰托夫原子能研究所,     

Three-Body Faddeev Approach to Two-Proton Emissions from iSNe Excited State

The proton drip line nucleus 18Ne is considered as a system of two protons and a 160 core. The excitation-energy spectrum of 18Ne and the relative-momentum distribution of the two protons emitted from the 6.15 MeV level of 18Ne are calculated using the Faddeev approach.     

垒下熔合的实验现状

引言本文讨论垒下熔合的实验现状。给出几个新近垒下熔合研究的结果,强调一些突出的问题和提出一些见解及回答。讨论垒下熔合过程已持续近三十五年之久。但是,随着新加速器能力和实验技术的发展,仅在过去五年左右的时间里,我们才能研究重原子核的这一基本过程。从这些研究我们了解到:(Ⅰ)垒下熔合的成份远大于用简单量子隧道所能解释的,在重系统中,能标可能偏移隧道值达10—20MeV。(Ⅱ)垒下熔合截面是碰撞体价结构的灵敏函数;当碰撞体的中子数改变时,在闭壳附近的截面特别灵敏,截面大小可能呈现复杂(非单调)的变化。     

杨立铭先生简历

【编者按】在我国著名理论物理和核物理学家杨立铭院士80岁寿辰之际,北京大学物理系和理论物理教研室举行庆祝会,表彰杨先生在科学研究和培养人才上的贡献．到会的有北京和各地的科学界和教育界人士100多人．会上北京大学校长陈佳洱院士和北京大学物理系主任甘子钊院士讲话祝贺,苏肇冰院士等10多人代表个人或单位讲话祝贺．庆祝会上还举行了学术研讨会,张焕乔院士和张宗烨院士等10多人作了学术报告．本期《原子核物理评论》作为祝贺杨先生80岁寿辰的论文集,刊登了杨先生的简历以及研讨会上的报告,其中有些报告因文稿未寄来,未能包括在内．此外,还刊登了艾小白先生以及马维兴先生和美国卡内基梅隆大学物理系Kisslinger教授为了庆贺杨先生寿辰而写的论文． 　　杨立铭先生,江苏溧水人,汉族,1919年2月5日出生． 　　杨先生从小勤奋好学,成绩优异,热爱祖国．在读高中的时候,家乡被日本侵略者占领,经过半年多的流离颠沛,逃难到了四川,痛感国家和民族所受的屈辱．1938年被保送入中央大学,他选择了机械系,希望对于发展工业振兴中华作出贡献．在大学学习过程中,又开始感到自己更向往于学习物理学、探索自然规律．于1942年大学毕业后,去昆明中央机械厂工作了一年,后又回到中央大学机械系任助教,同时学习数学和物理方面的课程．     

Dynamical Effects on Sub-barrier Fusion of ^40,48Ca＋^90,96Zr

We have measured the fusion cross sections for ^48Ca＋^90,96Zr around the Coulomb barrier and presented them along with the experimental data of ^40Ca＋^90,96Zr. The experimental results are compared with the improved quantum molecular dynamics model calculations. It is shown in comparison that the dynamical effects play an important role in the sub-barrier fusion reaction     

超重核合成的新进展

介绍了在充气分离器上用２４４Ｐｕ（４８ Ｃａ，３ｎ）２８９１１４和２０８ Ｐｂ（８４ Ｋｒ，ｎ）２９３１１８反应分别合成超重核２８９１１４和２９３１１８的新发现． Introduction of the first synthesis of new superheavy nuclei 289114 and 293118 in reactions of 48Ca+244 Pu and 86 Kr+ 208 Pb.