~(19)F+~(27)Al耗散反应产物截面测量中的不重复性

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114MeV和118．75MeV的19F+27Al 耗散反应产物B,C,N,O,F,Ne,Na和Mg的微分截面测量．条形27Al同位素靶的大小尺寸为 10mm×50mm,平均厚度约67μg／cm2．固定入射束流19F的能量,通过移动靶位,先后轰击了靶上20个不同的位置．实验结果表明,在弹靶系统、入射能量以及探测系统都相同的多次独立的微分截面测量中,截面的涨落不呈现高斯型几率分布．截面测量的这种不重复现象难以用有限计数率的统计性质来解释．

(19)~F+(27)~Al耗散反应中双核系统的转动与衰变

测量了19F+27Al耗散反应产物B,C,N,O,F和Ne的激发函数,入射束流的能量从110.25MeV 到118.75MeV,能量步长为250keV.用能量自关联函数方法从激发函数中提取了各反应产物的平均衰变宽度,利用同时考虑反应中所形成的中间双核系统的转动特性和衰变特性而发展了的Ericson核反应统计理论,讨论了19F+27Al耗散反应中双核系统随时间的演化过程.

~(19)F+~(27)Al反应产物的角分布、角分散与耗散机制

完成了114MeV19F+27Al深部非弹性碰撞产物的角分布测量.分析了反应产物B,C,N,O,F,Ne,Na,Mg和Al的实验室系角分布,讨论了反应形成的中间双核系统随时间演化过程中角分布所表现出的耗散特点.从实验上提取了反应产物各元素的角分散参数并作了角分散参数的理论拟合,讨论了角分散参数的物理意义以及角分散参数与耗散反应产物的电荷数Z之间的依赖关系.

~(19)F+~(27)Al深部非弹性碰撞产物的角分布

完成了19F+27Al深部非弹性碰撞产物的角分布测量.初步分析了反应产物B,C,N,O,F,Ne,Na,Mg和Al的实验室系角分布,展现出深部非弹性反应机制的特点,显示了反应系统随时间的演化过程.

~(19)F+~(93)Nb耗散反应产物不重复截面的分析

完成了19F +93 Nb耗散反应产物激发函数的两次独立测量 ,入射束流的能量从 10 2MeV到10 8MeV ,步长 2 5 0keV .实验结果在一些相同能量点两次测量的截面不能重复 .分析表明 :能量自关联函数的离散程度大约相当于随机计数率引起的离散程度的 3倍 ;激发函数曲线相对于能量平均本底的几率分布 ,有大约 2 1髎超出了标准高斯分布宽度的 3倍 ;两次测量得到的截面之差的几率分布大约有 18髎也超出了标准高斯分布宽度的 3倍 .可见 ,两次测量的19F +93 Nb耗散反应产物激发函数的截面不重复性具有明确的统计意义 ,其来源不是计数率的随机涨落 .

~(19)F+~(93)Nb耗散反应的相互作用时间

测量了1 9F + 93Nb耗散反应产物的激发函数与角分布 .从角分布的斜率提取的该反应系统的平均寿命在对称性较大的入射系统中反映了系统中耗散产物的特征时间 ;通过能量自关联函数方法从激发函数提取的反应时间不论在对称的还是在非对称的入射系统中都反映了耗散产物的特征时间 .能量自关联函数还可以给出双核系统的转动角速度以及表征转动阻尼的退相干宽度 ,更好地描述双核系统随时间的整个演化过程 .

~(19)F+~(93)Nb耗散反应产物激发函数中截面测量的不重复性

完成了 1 9F + 93Nb重离子耗散碰撞激发函数的两次独立测量 .束流的入射能量为 1 0 0— 1 0 8MeV ,步长 2 50keV .两次测量的宏观条件几乎完全一样 ,惟一的差别是使用了厚度分别为 70和 71 μg cm2 的两块 93Nb同位素靶 .实验结果表明 :( 1 )两次测量所得到的耗散反应产物激发函数的涨落具有不可平滑的结构 ;( 2 )这种不平滑的涨落截面有不重复的迹象 .着重从实验的角度对这一结果进行了讨论 .

~(19)F+~(93)Nb重离子耗散碰撞中截面测量的不可重复性(英文)

完成了１９Ｆ＋９３Ｎｂ重离子耗散碰撞激发函数的两次独立测量．束流１９Ｆ８＋的入射能量１００—１０８ＭｅＶ，能量步长２５０ｋｅＶ；两次测量中分别使用了厚度为７０和７１μｇ／ｃｍ２的９３Ｎｂ靶，其它宏观实验条件（例如，入射能量及能量步长，探测器及其探测角度，加速器、电子学以及数据获取系统的参数选取等等）则保持完全相同．实验结果表明，两次测量所得到的耗散产物截面的激发函数的不平滑结构具有不可重复性．这一实验结果支持了最近提出的理论预言：“在复杂量子碰撞中存在对初始条件的极端敏感性与混沌运动．”

同位旋相关的Boltzmann-Langevin方程及新核素~(19)Na产生截面的研究

介绍了一种同位旋相关的输运方程 ,研究了在入射能量为 2 8.7和 6 0 .0MeV/u时　 12 C +12 C的反应 ,对模型进行检验 ,发现计算结果较好地符合实验结果 ,说明了方程的可靠性 .利用该模型研究了在入射能量为 2 8.7MeV/u下反应系统17— 2 0 ,2 2 Ne+12 C中核素19Na的产生截面 ,发现缺中子核引起的反应 ,具有更大19Na的产生截面 ,为新核素的探测找到了理论依据 .

50MeV/u~(20)Na+~(208)Pb→p+~(19)Ne+~(208)Pb反应的探测效率模拟

用半经典模型考虑20Ｎａ＋２０８Ｐｂ→ｐ＋１９Ｎｅ＋２０８Ｐｂ的Ｃｏｕｌｏｍｂ解离过程。用ＭｏｎｔｅＣａｒｌｏ方法计算前角放置的望远镜阵列对Ｃｏｕｌｏｍｂ解离碎片的探测效率。讨论了天体环境下ｐ＋１９Ｎｅ→２０Ｎａ俘获反应道的低能级共振截面测量的可行性。

Cross-correlation of excitation functions for different fragments and different scattering angles in Al-27(F-19, x)y reactions

Excitation functions have been measured for different projectile-like fragments produced in Al-27(F-19,x)y reactions at incident energies from 110.25 to 118.75 MeV in 250 keV steps. Strong cross section fluctuations of the excitation functions are observed. The cross- correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle theta(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 Al-27(F-19,x)y.

Largely deformed dinuclear system formed in F-19+Al-27 dissipative collision

Excitation functions are measured for different charge products of the F-19+(27) Al reaction in the laboratory energy range 110.25-118.75MeV in steps of 250keV at theta(lab) = 57 degrees, 31 degrees and -29 degrees. The coherence rotation angular velocities of the intermediate dinuclear systems formed in the reaction are extracted from the cross section energy autocorrelation functions. Compared the angular velocity extracted from the experimental data with the ones deduced from the sticking limit, it is indicated that a larger deformation of the intermediate dinuclear system exists.

Rotation and deformation of the dinuclear system formed in dissipative reaction of F-19+Al-27

Excitation functions of the reaction products B, C, N, O, F and Ne emitted from the dissipative reaction of (19) F+(27) Al have been measured at incident energies from 110.25MeV to 118.75MeV in steps of 250keV. The moments of inertia of the intermediate dinuclear system formed in the reaction are extracted from the energy autocorrelation functions of the products. Comparing the moment of inertia extracted from the experimental data with the calculated one by using the sticking limit, it indicates that the formed dinuclear system has a large deformation in the reaction process.

Non-reproducibility of the cross sections of the products induced from dissipative reaction of F-19+Al-27

The differential cross sections of the dissipative products B, Q N, O, F, Ne, Na and Mg induced from the reactions of F-19+Al-27 at two incident energies have been measured at the HI-13 tandem accelerator, Beijing. In the case of a fixed beam incident energy 114MeV or 118.75MeV respectively, identical reaction system and the same detection system, 20 target points in steps of 2mm on(.)a 10mmx50mm rectangular Al foil have been bombarded. The experimental results indicate that the probability distribution of the cross sections is much wider than a standard Gaussian distribution. This non-reproducibility of the cross sections can't be interpreted by the statistical property of a finite count rate.

Thermal-shock resistance of LnMgAl(11)O(19) (Ln = La, Nd, Sm, Gd) with magnetoplumbite structure

Lanthanide hexaaluminates including LaMgAl11O19, NdMgAl11O19, SmMgAl11O19 and GdMgAl11O19 were synthesized via Sol-Gel method. Due to the anisotropic crystal growth, these oxides crystallize in the form of platelets and the platelet thickness increases with the decrease of rare-earth ionic radius. It was observed that the thermal-shock resistances of LaMgAl11O19, NdMgAl11O19 and SmMgAl11O19 oxides were superior to 8YSZ as proved by water quenching tests. In addition, the thinner the platelet. the more interstices are retained in the sintered specimen, and the better thermal-shock resistance the oxide has. Based on SEM images, it can be seen that the SmMgAl11O19 sample exhibits a mixture of the intergranular and transgranular fracture after thermal cycling failure.