Half-life measurement of 133mCe with $ \gamma$ -spectrometry

In this paper we describe our experiment determining the half-life of ^133mCe . An activation-based nuclear-reaction cross-section measurement has been carried out for the ¹³⁰Ba(a \alpha, n)^133mCe reaction, in order to improve our knowledge of the astrophysical p-process. For the analysis of such a measurement, the precise knowledge of the decay half-life of the reaction product is desired. In the case of ^133mCe the literature half-life value has only been known with a high relative uncertainty. A measurement utilizing g \gamma -spectrometry has been carried out to refine the half-life of ^133mCe . As a result, the new recommended half-life is t _1/2 = (5.326±0.011) h. This value has been found to be consistent with the previous literature value, while its uncertainty has been reduced by more than a factor of 30.     

激光跟踪测量系统自校正方法研究

建立了测量系统运动学模型。针对以往在球坐标激光跟踪系统中参考点只能借助于外部更高精度的仪器来校正的缺点,提出了平面约束自校正方法,并对系统进行了自校正研究。仿真结果表明了该方法的有效性。     

γ光闪烁体阵列的非均匀响应相对校正方法

 闪烁体阵列常用于辐射图像探测,基于闪烁体阵列存在严重的响应非均匀性,提出了相对校正方法,在无需知道光源参数、CCD相机参数及光学系统参数的前提下,利用本底图像、空场图像和被测样品辐射图像,得到被测物体对γ光的衰减分布。并进行了验证实验,结果表明：此方法不但可以消除响应的非均性的影响,而且可以消除辐射源固有分布的影响。     

Half-life and α-ray energy of146Sm

Up-to-date α-decay data of the double-even,N=84 isotones are presented, including the presently remeasured values for¹⁴⁶Sm. For this nuclide a half-life,T _1/2 =1.031 (45) ×10⁸ y, and α-ray energy, E_α=2455(4) keV, were measured. The significance of these data for the subshell closure atZ=64 observed in α-decay is discussed.     

Inclusive D production in $\gamma \gamma$ collisions: including the single-resolved contribution with massive quarks

We have calculated the next-to-leading order cross section for the inclusive production of charm quarks as a function of the transverse momentum p_T and the rapidity in two approaches using massive or massless charm quarks. For the single-resolved cross section we have derived the massless limit from the massive theory. We find that this limit differs from the genuine massless version with factorization by finite corrections. By adjusting subtraction terms we establish a massive theory with subtraction which approaches the massless theory very fast with increasing transverse momentum. With these results and including the equivalent results for the direct cross section obtained previously as well as double-resolved contributions, we calculate the inclusive cross section in collisions using realistic evolved non-perturbative fragmentation functions and compare with recent data from the LEP collaborations ALEPH, L3 and OPAL. We find good agreement. Received: 14 February 2003 / Published online: 5 May 2003     

Vision of nuclear physics with photo-nuclear reactions by laser-driven $\sf \gamma$ beams

A laser-accelerated dense electron sheet with an energy \(E=\tilde{\gamma} mc^2\) can be used as a relativistic mirror to coherently reflect a second laser with photon energy ?ω, thus generating by the Doppler boost [A. Einstein, Annalen der Physik 17, 891 (1905); D. Habs et al., Appl. Phys. B 93, 349 (2008)] brilliant high-energy photon beams with \(\hbar\omega^{\prime}=4\tilde{\gamma}^2\hbar\omega\) and short duration for many new nuclear physics experiments.While the shortest-lived atomic levels are in the atto-second range, nuclear levels can have lifetimes down to zeptoseconds. We discuss how the modulation of electron energies in phase-locked laser fields used for as-measurements [E. Goulielmakis et al., Science 317, 769 (2007)] can be carried over to the new direct measurement of fs–zs nuclear lifetimes by modulating the energies of accompanying conversion electrons or emitted protons. In the field of nuclear spectroscopy we discuss the new perspective as a function of increasing photon energy. In nuclear systems a much higher sensitivity is predicted to the timevariation of fundamental constants compared to atomic systems [V. Flambaum, arXiv:nucl-th/0801.1994v1 (2008)]. For energies up to 50 keV Mössbauer-like recoilless absorption allows to produce nuclear bosonic ensembles with many delocalized coherent polaritons [G.V. Smirnov et al., Phys. Rev. A 71, 023804 (2005)] for the firsttime. Using the (γ,n) reaction to produce cold, polarized neutrons with a focusing ellipsoidal device [P. Böni, Nucl. Instrum. Meth. A 586, 1 (2008); Ch. Schanzer et al., Nucl. Instrum. Meth. 529, 63 (2004)], brilliant cold polarized micro-neutron beams become available. The compact and relatively cheap laser-generated γ beams may serve forextended studies at university-based facilities.     

Variation of γ-ray spectra with the energy of channeled electrons

The spectral dependence of the γ-radiation produced by channeled electrons of different energies, E = 600, 750 and 900 MeV in 0.35 mm thick diamond was measured with a NaI(Tl) photon spectrometer. The energy dependences of the basic spectral features of the channeling radiation were determined.     

Application of α——β——γ filtering to real-time atmosphere methane concentration measurement

A real time $\alpha$--$\beta$--$\gamma$ filtering technique is applied to the monitoring of atmosphere CH可调二极管激光吸收光谱 谐波检测 物理光学 激光技术tunable diode laser absorption spectroscopy, multi-pass cell, harmonic detectionProject supported by the National Natural Science Foundation of China (Grant No 10274080) and the National High Technology Research and Development Program of China (Grant No 2003AA641010).8/5/2005 12:00:00 AM2005-08-052006-01-19A real time α-β-γ filtering technique is applied to the monitoring of atmosphere CH4 based on a tunable diode laser spectrum system operating at 1.654μm. This technique is developed for improving the sensitivity and precision of CH4 concentration measurement with slow concentration change. The effectiveness of this technique is evaluated by performing CH4 concentration measurement and using it to monitor the varying methane level in the atmosphere. It was proved that signal noise ratio enhancement factor is 4.25. The comparison between this filter and moving average is also included in this article. It indicates the advantage of the α-β-γ real time filter.     

导弹跟踪能力的目标源与条件保障车的设计

为了验证实验室环境下红外导引头跟踪能力的精度,设计了一套模拟飞行目标能量分布的目标源以及一款能够满足相应姿态条件的保障车。采用焦距为700 mm的离轴抛物面反射镜,满足2′束散角的要求,利用多个反射镜及离轴镜构成反射式平行光管,模拟空间距离,通过1%和10%两片衰减片与光阑孔调节,实现三档能量的需要。采用微调升降机构实现0°~10°俯仰角的调节,滚转机构用以满足0°~10°的滚转角调节,运用液压升降机构达到0~1 000 mm升降指标。依靠力学计算和静力学分析,得出升降臂的最大变形量为0.11 mm,最大应力为111.6 MPa,能够满足1 000 kg负载的要求,同时车架的模态分析所得到的一阶振型的固有频率为25.355 Hz,远大于产生共振的条件,满足所设计的目标源和条件保障车指标要求。     

Controlling the charging energy of arrays of tunnel junctions

We describe a new technique to control in situ charging energy of systems of coupled metallic or superconducting islands. To illustrate the technique, we have fabricated two-dimensional arrays of Al islands on GaAs/AlAs heterostructures. Each island is coupled to its nearest-neighbor by a submicron Al/AlO_x/Al tunnel junction and to the three-dimensional electron gas (3DEG) located below the surface of the heterostructure by a capacitance C_g. We vary C_g, which dominates the charging energy of the array, by depleting the electrons in the 3DEG by means of a negative voltage applied to the array. With the array driven normal by a magnetic field, a decrease in C_g increases in both the offset voltage and the period of the Coulomb blockade oscillations.     

Masses and couplings of vector mesonsfrom the pion electromagnetic,weak, and $\pi\gamma$ transition form factors

We analyze the pion electromagnetic, charged-current, and transition form factors at timelike momentum transfers q, GeV², using a dispersion approach. We discuss in detail the propagator matrix of the photon-vector meson system and define certain reduced amplitudes, or vertex functions, describing the coupling of this system to final states. We then apply the derived analytic expressions to the analysis of the recent , , and data. We find the reduced amplitudes for the coupling of the photon and vector mesons to two pseudoscalars to be constant, independent of s, in the range considered, indicating a freezing of the amplitudes for GeV. The fit to the form factor data leads to the following values of the Breit-Wigner resonance masses MeV, MeV and MeV, where the errors are only statistical.Received: 8 December 2003, Published online: 23 March 2004T. Paulus: Now at Philips     

Solving the coincidence problem: tracking oscillating energy

Recent cosmological observations strongly suggest that the Universe is dominated by an unknown form of energy with negative pressure. Why is this dark energy density of order the critical density today? We propose that the dark energy has periodically dominated in the past so that its preponderance today is natural. We illustrate this paradigm with a model potential and show that its predictions are consistent with all observations.     

A windowless hydrogen gas target for the measurement of 7Be(p, $ \gamma$ )8B with the recoil separator ERNA

Using the Coulomb and proximity potential model (CPPM) we have investigated the cluster decays of the isotopes ^212-240Pa, ^219-245Np, ^228-246Pu, ^230-249Am and ^232-252Cm leading to doubly magic ²⁰⁸Pb and its neighboring nuclei, which are not experimentally detected but which may be detectable in the future. It is found that most of the decays are favourable for experimental measurements (i.e., $T_{1/2}<10^{30}$ s) and this observation will serve as a guide to future experiments. Our study reveals the role of doubly magic ²⁰⁸Pb daughter nuclei and near doubly magic nuclei in the cluster decay process. In order to make a comparison with CPPM we also calculated the logarithmic half-lives using the Universal formula for the cluster decay (UNIV) by Poenaru et al., the Universal Decay Law (UDL) and the Scaling Law of Horoi et al., and they are found to be in good agreement. The Geiger-Nuttall plots of $log_{10}(T_{1/2})$ versus $Q^{-1/2}$ for various clusters from different isotopes of heavy parent nuclei have been studied and are found to be linear.     

基于方位-频率及多阵方位的无源目标跟踪性能研究

研究了两种利用多维信息的目标运动分析(TMA)方法:方位-频率TMA和多阵联合纯方位TMA,应用Gauss-Newton(G-N)和Levenberg--Marquardt(L-M)相结合的最优化方法,分析了最大似然估计(MLE)算法的跟踪性能,进行了仿真实验.研究结果表明利用多维信息的TMA虽然克服了常规纯方位TMA需要观测平台机动的限制,但其应用并不具备普遍性。     

一种多基阵机动目标被动跟踪算法

由多部声纳基阵获取的方位信息对水中机动目标的跟踪实质上是一个非线性状态估计问题,文中首先依据各基阵的方位信息,采用最小二乘法得到目标位置在各采样时刻的初步估计,然后将其作为测量值用于交互多模型算法(IMM)并结合线性卡尔曼滤波(KF)得到目标运动速度和轨迹,避免了应用非线性估计算法直接进行多个方位数据融合过程中存在的各种问题。仿真结果表明这一算法简便,与双基阵纯方位机动目标被动跟踪相比具有较快的收敛速度和较高的跟踪精度。     

单光子探测器量子效率的绝对自身标定方法

提出一种单光子探测器量子效率的绝对自身标定方案，利用光参量下转换过程中产生的光子对在时间上的相关性，先将参量光束分为两路，然后引入相对延时，使同时产生的孪生光子先后进入单光子探测器，然后将探测器之后的电路分为三路，其中一路直接进入计数器得到探测器所探测到的光子的总计数率，另两路用电路方法引入和光路相当的相对延时，经符合电路后进入计数器，得到前后到达探测器的光子对之间的符合计数率.这样，从符合计数率与总光子计数率之比即可在不需要任何其他探测器或者参照标准的情况下获得探测器的量子效率.文中给出两种方案，分别适