Clover探测器的极化测量

介绍了利用Colver探测器测量γ射线的线性极化方法. 用⁶⁰Co源对其进行测试, 有效地测量了γ射线的电磁属性, 从而确定了能级的宇称.     

Investigation of add-back effects in a segmented Clover detector

The resolution and the summing characteristics of an EXOGAM segmented Clover germanium detector has been studied for use it in y spectroscopic experiments. The measurements have been performed with standard radioactive sources of ^152Eu, ^133Ba and β-delayed γ-rays from 176Ir decay. The data analytic results, realized by software, are presented in this paper.     

Investigation of add-back effects in a segmented Clover detector

The resolution and the summing characteristics of an EXOGAM segmented Clover germanium detector has been studied for use it in γ spectroscopic experiments. The measurements have been performed with standard radioactive sources of 152Eu, 133Ba and β-delayed γ-rays from 176Ir decay. The data analytic results, realized by software, are presented in this paper.     

An actively vetoed Clover \gamma -detector for nuclear astrophysics at LUNA

An escape-suppressed, composite high-purity germanium detector of the Clover type has been installed at the Laboratory for Underground Nuclear Astrophysics (LUNA) facility, deep underground in the Gran Sasso Laboratory, Italy. The laboratory $ \gamma$ -ray background of the Clover detector has been studied underground at LUNA and, for comparison, also in an overground laboratory. Spectra have been recorded both for the single segments and for the virtual detector formed by online addition of all four segments. The effect of the escape suppression shield has been studied as well. Despite their generally higher intrinsic background, escape-suppressed detectors are found to be well suited for underground nuclear-astrophysics studies. As an example for the advantage of using a composite detector deep underground, the weak ground-state branching of the E _p = 223 keV resonance in the ²⁴Mg(p, $ \gamma$ )²⁵Al reaction is determined with improved precision.     

Spontaneous ternary fission of 252Cf: New experiment with GSI super clover detectors

A new multiparameter experiment on ternary fission of ²⁵²Cf has recently been successfully performed by using the CODIS2 detector system and two GSI segmented Super Clover Ge γ-ray detectors. The experimental setup and the main subjects of interest are briefly described.     

Parity of the band head at 3710 keV in 99Rh using clover detector as compton polarimeter

Clover detector has been used as a Compton polarimeter to measure the linear polarization of γ-rays produced in heavy ion fusion reaction. The polarization sensitivity of the clover detector has been measured over γ-ray energies ranging from 386 to 1368 ke V. The E1 multipolarity of the 1117 keV transition in ⁹⁹Rh has been established using this polarimeter. This has resulted in the assignment of negative parity to the band head at 3710 keV in ⁹⁹Rh.     

Gamma-ray spectroscopy with relativistic exotic heavy-ions

Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.     

HIO3分子的密度泛函理论研究

利用密度泛函理论对于HIO3分子的异构化及其消去反应势能面进行了细致的研究.B3LYP结合混合基组,对于O和H原子使用6-311 G(3df,3pd)基组,对于I原子使用3-21G基组,进行结构优化,振动频率计算以及电子拓扑学分析.在势能面上八个稳定的异构体结构被找到,经过计算稳定性如下:HOIO2-1>HOOOI-2>HOOOI-1>HOIOO-1>HOIOO-2>HOIO2-2>HIO3-1>HIO3-2,此外,势能面上存在三种稳定的松散复合物.对于势能面上IO HO2,OIO OH和IOO OH的反应机理进行了详细的讨论.利用振动模式分析的方法对于反应物,中间体,过渡态以及产物之间的关系进行明确的分析.此外,还应用电子密度拓扑学对于异构化及其消去过程进行分析.     

Eigenvalues and eigenfunctions of a clover plate

We report a numerical study of the flexural modes of a plate using semi-classical analysis developed in the context of quantum systems. We first introduce the Clover billiard as a paradigm for a system inside which rays exhibit stable and chaotic trajectories. The resulting phase space explored by the ray trajectories is illustrated using the Poincare surface of section, and shows that it has both integrable and chaotic regions. Examples of the stable and the unstable periodic orbits in the geometry are presented. We numerically solve the biharmonic equation for the flexural vibrations of the Clover shaped plate with clamped boundary conditions. The first few hundred eigenvalues and the eigenfunctions are obtained using a boundary elements method. The Fourier transform of the eigenvalues show strong peaks which correspond to ray periodic orbits. However, the peaks corresponding to the shortest stable periodic orbits are not stronger than the peaks associated with unstable periodic orbits. We also perform statistics on the obtained eigenvalues and the eigenfunctions. The eigenvalue spacing distribution P(s) shows a strong peak and therefore deviates from both the Poisson and the Wigner distribution of random matrix theory at small spacings because of the C_4v symmetry of the Clover geometry. The density distribution of the eigenfunctions is observed to agree with the Porter-Thomas distribution of random matrix theory. Received 12 February 2001 and Received in final form 17 April 2001     

Euroball: Present status and outlook

Euroball is a European project to build a highly efficient and powerful gamma-ray spectrometer for nuclear structure spectroscopy. The project is an amalgamation of recent technical advances in detectors, electronics and data acquisition. In the first phase the spectrometer consists of 30 large single crystal Ge detectors, 26 Clover Ge detectors and 15 Cluster Ge detectors each with an associated suppression shield. The 239 individual Ge detector elements will have a total photopeak efficiency ∈ _p of ≈ 10% and will enable the properties of the atomic nucleus to be studied with a sensitivity up to or better than 10^?5 of the production cross-section. The elements of the spectrometer, including the detectors, the electronics and the data acquisition system, some of the planned ancillary detectors and the first results will be presented. Several developments are under investigation for the upgrade of Euroball for its second phase. These include an inner BGO ball for multiplicity and summed energy determination and inner particle detectors for charged particle identification. These developments will also be discussed.     

H2SiCl2 中 SiH 伸缩振动的泛频光谱

在2000 ～ 9000 波数 、 12000 ～12900 波数的光谱区间记录了室温下H2SiCl2气体分子的振动泛频光谱，所用的仪器分别是高分辨傅立叶变换光谱仪和高灵敏激光腔内吸收光谱仪。用局域模模型和包含达林－丹尼生共振的简正模模型，归属了SiH伸缩振动的基频和泛频，振动量子数的改变△VSiH=1, 2, 3, 4 and 6。通过对实验能级的非线性拟合，得到SiH伸缩振动的谐振频率ωm、非谐性常数χm、键间耦合系数λ、莫尔斯振子参数 De、α 和相互作用力常数 。实验发现，随着振动能量的增加，振动簇（manifold，两个SiH键的伸缩振动量子数m+n=常数 ）中能量最低的两个能级的间距逐渐减小。当△VSiH≥4时，在实验误差范围内这两个最低的振动态能级简并。这种简并的能级结构类似双原子莫尔斯振子，符合Birge-Sponer 关系。双原子莫尔斯振子直接描述了H2SiCl2分子中SiH 的高泛频伸缩振动，表明在高振动情况下振动能量已经集中到单个SiH键上。     

Gamma spectroscopy of neutron-rich nuclei with the CLARA-PRISMA setup

The CLARA-PRISMA experimental set-up combines the large acceptance magnetic spectrometer for heavy ions PRISMA with the highly efficient CLARA array of 25 Clover detectors. Selected results on the structure of neutron-rich nuclei, populated in multinucleon transfer and deep-inelastic reactions, are presented here. Some technical developments of the setup are also discussed.     

30MeV/u 40Ar+natAg反应中中等质量碎片的发射时标

采用强度干涉技术,研究了30MeV/u ⁴⁰Ar+^angAg反应中IMF-IMF关联的实验结果.利用三体弹道模型从约化速度关联函数提取了中等质量碎片的发射时间.中等质量碎片的平均发射时间随其能量而变化,从低能时的约300fm/c下降到高能时的约100fm/c.扣除类弹碎片的贡献后,得到此反应发射中途中等质量碎片的平均发射时间约为250fm/c,表明此反应发射的中等质皇碎片主要来自于相继两体衰变.     

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基于托卡马克实验的L-H模转换过程中等离子体的输运特征,建立了一种简化的非线性等离子体输运模型。通过数值求解输运方程,得到了等离子体稳态温度分布剖面,成功模拟了托卡马克边缘输运势垒(ETB)的形成以及高辅助加热功率下的内部输运势垒(ITB)现象,并对比了有无输运势垒两种情况下托卡马克的能量约束效率。     

时间反演对称性破缺系统中的拓扑零能模

Su-Schreiffer-Heeger模型预测了在一维周期晶格的边缘处可能出现零维的拓扑零能模,其能量本征值总是出现在能隙的正中间.本文以半导体微腔阵列中光子和激子在强耦合情况下形成的准粒子为例,通过准粒子的自旋轨道耦合与Zeeman效应,研究了时间反演对称性破缺对拓扑零能模的影响.发现拓扑零能模的能量本征值可以随着自旋轨道耦合强度的变化在整个带隙内移动,自旋相反的模式移动方向相反;在二维微腔阵列中发现了沿着晶格边缘移动的拓扑零能模,提出了一维零能模的概念.由于时间反演对称性的破缺,这种一维拓扑零能模解除了在相反传输方向上的能级的简并,从而在传输过程中出现极强的绕过障碍物的能力.     

光纤回音壁模式激光产生长度的实验与理论研究

采用沿光纤轴向光抽运消逝场激励增益的方式,获得了沿光纤轴向较长范围的回音壁模式激光辐射.研究了这种激光器的激光产生长度与抽运能量间的关系.实验发现:当抽运能量刚超过激光产生阈值时,激光产生长度迅速增长;随抽运能量的继续增加,产生长度的增长趋势变缓;产生长度随抽运能量的变化关系决定于增益包层溶液的染料浓度和溶液折射率.根据抽运光沿光纤轴向以受抑全反射方式传播的物理特性,在抽运能量中引入了遵循比尔吸收定律的指数衰减函数,结合消逝场激励增益的回音壁模式激光理论,在分析系统增益和损耗的基础上由激光阈值条件推导出了 关键词： 回音壁模式 受抑全反射 消逝场 激光产生长度     

Scaling of Yb-doped photonic crystal fiber to 200 μm core diameter for high beam quality laser output

The rare earth-doped active fibers not only have ten thousands of square-micron core-area but also deliver a laser with near-diffraction-limited beam quality. However, they have been studied little. In this paper, we design a 200-μm-corediameter Yb~(3+)-doped photonic crystal fiber with a large pitch in the air-hole cladding region. Simulations demonstrate that only fundamental mode(FM) with a mode field area(MFA) of ～ 28000 μm~2 can be amplified and propagated at the gain saturation, and the beam quality M~2 is about 1.5. It is predicted that almost 105 m J single-pulse energy is available from such a 1.5-meter-length fiber.     

甲苯酚第一激发态的共振多光子电离谱

测量了间位甲苯酚和甲酚异构体混合物能量在３５１８０－３６００２ｃｍ＾－１范围的双光子共振四光子电离谱。对第一电子激发态振动带做了分析和归属，并对苯分子的不同取代对振动模的影响做了比较和分析。     

环内选模对撞锁模激光器能量输出特性研究

环内选模Nd:YAG激光器的输出能量比环外选模的输出能量提高了近一倍,而且激光器的其它性能也有了很大的改善．本文从理论和实验上对环内选模激光器的能量输出特性进行了分析和研究,该研究对激光器模式选择方式及方法具有指导意义．     

同轴虚阴极谐振效应研究

中国工程物理研究院应用电子学研究所的一些实验表明由阳极反射板、阳极网和阴极发射的电子束形成的环状虚阴极围成的准谐振腔是决定同轴虚阴极输出微波功率和传输模式的关键所在. 在二极管电压350kV，电流23kA条件下，获得了500MW的微波输出功率，能量转换效率约6.2％，工作频率3.3GHz，输出微波主要由TM₀₁模式和TE₁₁模式组成. 对同轴虚阴极的谐振效应进行了分析. 关键词： 高功率微波 同轴虚阴极 谐振腔 模式竞争