启明星Ⅱ次临界非稳态热中子注量率测量

中子注量率及分布是反应堆的重要参数，本工作通过核数守恒在非稳态情况下的推导和求解，从理论上论证了次临界反应堆非稳态情况下中子注量率测量的可行性。将活化法和固体径迹法有机结合，利用固体径迹探测器标定活化片的测量数据，测量了启明星Ⅱ零功率装置的He-3管实验孔道内及反应堆外壁的中子注量率的分布，并与模拟计算结果进行了比较，利用MCNPX程序得到的模拟计算结果与实验结果的趋势一致，证明了该测量方法可以测量低通量的中子注量率，可实现反应堆不同时刻、不同位置的中子注量率测量，为CiADS技术的研发提供了实验数据与技术支撑。Neutron flux measurements were carried out at VENUS-Ⅱ lead-based zero power reactor by neutron activation method combined with solid-state nuclear track detectors (SSNTD). This experimental method was proposed based on the principle of nuclear number conservation when a foil was irradiated in an unsteady-state neutron field. By this method, thermal neutron flux distributions inside the He-3 duct were measured when VENUS-Ⅱ was operated under unsteady-state. The neutron flux distributions were also calculated with MCNPX code and were consistent with the experimental data. In addition, the neutron fluxes in the outer layer of VENUSⅡ were measured under steady-state. These results would benefit the further study of experimental methods for neutron flux measurement and provide important support for the design of CiADS.     

利用α关联衰变链鉴别新同位素_(107)~(265)Bh

主要介绍了合成和鉴别107号元素的新同位素265Bh的实验装置、实验方法以及实验结果.目标核265Bh是由能量为135MeV的26Mg离子轰击243Am靶,通过融合蒸发反应而产生.反应产物首先由He jet系统传输到装有数个探测器对的转轮收集测量系统,然后依靠母子核遗传关系通过观察新同位素和它们已知子核261Db和257Lr之间的α衰变的关联,来实现对新核素的鉴别.实验测得265Bh的α衰变能量为(9.24±0.05)MeV, 半衰期为0.94+0.70-0.31s.从该实验得出的265Bh的α衰变能量和半寿命能够与理论预言一致.     

High-Spin States in Odd-Odd ^140Pr Nucleus

High-spin level structure of doubly odd nucleus ^140Pr has been investigated via the ^130Te(^14N,4n)^140Pr reaction at beam energies from 55 to 65 MeV. Measurements of γ-ray excitation functions, γ-ray singles and γ-γ-t coincidences were performed with twelve BGO(AC)HPGe detectors. The level scheme of ^140Pr, including 27 new levels and 42 new γ rays, has been established for the first time. The level structure is compared with those in the neighbouring odd-odd nuclei, and interpreted qualitatively.     

134Ba能级结构的在束γ谱学研究

利用在束γ谱学技术,通过¹²⁸Te(¹⁰B,1p3n)¹³⁴Ba反应研究了¹³⁴Ba的中、高自旋激发态.实验中采用9套BGO(AC)HPGe探测器进行了γγt符合测量.基于γγ符合关系、γ射线的相对强度和各向异性度的测量结果建立了¹³⁴Ba的能级纲图.比较N=78的同中子素链的负宇称能级结构的系统性,发现激发能位于4142keV,Jπ值为11^－的能级很可能是与¹³⁶Ce具有相似内禀结构特征的相似态     

~(190)Tl的πh_(9/2)νi_(13/2)扁椭球转动带的旋称反转研究(英文)

利用能量为 1 6 7— 1 75MeV的35Cl束流 ,通过16 0 Gd(35Cl,5n)熔合蒸发反应研究了190 Tl的高自旋态能级结构 .实验建立了190 Tl基于πh9/2 　 　νi13/2 组态的转动带 .在束测量结果和194 Biα衰变的α γ测量结果确定地指定了190 Tl的πh9/2 　 　νi13/2 转动带的自旋值 .基于自旋指定 ,发现了190 Tl的πh9/2 　 　νi13/2 扁椭球转动带在低自旋时旋称反转 .这是首次在基于πh9/2 　 　νi13/2 组态的扁椭球转动带中观测到旋称反转 .考虑了质子 -中子剩余相互作用的粒子 -转子模型能够解释πh9/2 　 　νi13/2 扁椭球转动带的低自旋旋称反转 .     

190Tl的πh9/2⊙νi13/2扁椭球转动带的旋称反转研究

利用能量为167—175MeV的35Cl束流,通过160Gd(35Cl,5n)熔合蒸发反应研究了190Tl的高自旋态能级结构.实验建立了190Tl基于πh9/2 νi13/2组态的转动带.在束测量结果和194Biα衰变的αγ测量结果确定地指定了190?Tl的πh9/2 νi13/2转动带的自旋值.基于自旋指定,发现了190Tl的πh9/2 νi13/2?扁椭球转动带在低自旋时旋称反转.这是首次在基于πh9/2 νi13/2?组态的扁椭球转动带中观测到旋称反转.考虑了质子–中子剩余相互作用的粒子–转子模型能够解释πh9/2 νi13/2扁椭球转动带的低自旋旋称反转.     

双奇核170Re中πh11/2⊙νi13/2带的实验观测及其系统学分析

通过束流能量为166MeV的重离子熔合蒸发反应¹⁴²Nd(³²S,1p3nγ)¹⁷⁰Re, 用在束γ谱学方法研究了¹⁷⁰Re的高自旋激发态, 首次观测到了双奇核¹⁷⁰Re的转动带能级纲图. 应用推转壳模型的基本理论, 进行了简要讨论. 在系统学上发现该转动带与A=170核区双奇核中πh_11/2⊙νi_13/2组态带的旋称劈裂特征及规律相符.     

Study of neutron spectra in a water bath from a Pb target irradiated by 250 MeV protons

Spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with a cadmium (Cd) cover. According to the measured activities of the foils, the neutron flux at different resonance energies were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code. The comparison showed that the simulation could give a good prediction for the neutron spectra above 50 eV, while the finite thickness of the foils greatly effected the experimental data in low energy. It was also found that the resonance detectors themselves had great impact on the simulated energy spectra.     

缺中子176Ir核β+/EC衰变研究

在210MeV的束流能量下, 利用重离子熔合蒸发反应¹⁴⁶Nd(³⁵Cl, 5nγ)¹⁷⁶Ir产生具有β⁺/EC衰变性质的核素¹⁷⁶Ir,由氦喷嘴快速带传输系统将反应产物传送到低本底区进行测量. 经过实验数据的离线处理分析,对早先发表的¹⁷⁶Ir衰变γ跃迁进行确认的同时又发现了3个新能级和10条新的γ射线, 丰富了¹⁷⁶Os核的低位激发态能级纲图. 并根据典型γ射线的衰变时间谱建议了¹⁷⁶Ir核的一个长寿命的低自旋同核异能态.     

奇奇核90Nb的高自旋态研究

用能量为80MeV的19F束通过反应76Ge(19F,5n)90Nb布居了90Nb的高自旋态.通过在束γ测量分析90Nb退激γ射线的符合级联关系,发现了19条新的属于90Nb的γ跃迁,建立了90Nb的高自旋态能级纲图.通过经验壳模型计算指定了部分能级的组态,并结合实验DCO比值和与相邻N=49核素的系统比较,确认了新能级的自旋和宇称. The high spin states of~(90)Nb have been populated via reaction~(76)Ge(~(19)F, 5n)~(90)Nb at beam energy of 80 MeV. The de-exciting γ-rays have been measured with in-beam γ-ray spectroscopy method. After γ-γ coincidence analysis, 19 new γ transitions were identified and assigned to~(90)Nb. The new level scheme of~(90)Nb was established. Based on the semi-empirical shell model calculations, the configurations of the levels have been suggested. In addition, the spins and parities of the new levels ...