长焦距光学系统杂光系数测试仪

报告了一种新的长焦距光学系统杂光系数测量装置,该装置除具有避免了制作大直径积分球的优点外,还能精确测量轴外杂光系数,分析各部分杂光源对杂光系数的影响.     

重复频率纳秒脉冲源程控脉冲发生器

介绍了一种可以完成脉宽、幅值、频率可调、十路脉冲输出且延时可调功能的程控脉冲发生器。硬件主要包括主电源和辅助电源、功率放大电路、控制系统处理器、数字键盘和液晶显示屏。该脉冲发生器输出脉冲宽度可在1~30 s间调节,脉冲幅值在1~15 V间调节,输出脉冲频率范围为1 Hz~30 kHz,十路脉冲输出中每路脉冲之间可以在0~1 ms范围内精确调节。该脉冲发生器可为多个脉冲源的并联运行提供延时触发,为多个绝缘栅双极型晶体管(IGBT)开关串联提供同步触发。     

用地面阵列寻找TeV能区γ点源的方法探讨

文中探讨搜寻TeV能区γ点源的方法.讨论利用student变量t判断来自源区及背景区宇宙线事例的统计差别,并由Bayes定理与MonteCarlo模拟相结合计算源区各能段的信号数,推算蟹状星云在TeV能区的γ射线微分能谱     

利用网络资源进行四级物理实验的科研设计

以科研实验为主题的大学四级物理实验,其目的是引导学生科研入门以及培养锻炼其科研能力。中国科学技术大学物理实验中心在这方面做了许多有益的探索。     

The REX-ISOLDE project

The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE. This revised version was published online in July 2006 with corrections to the Cover Date.     

红外无损探测中多宗量多热源反演问题的研究

为研究红外无损探测稳态多热源反演逆问题, 建立不同形状的均质与非均质稳态热传导模型, 其中内热源个数、位置、强度、面积均为未知项. 基于数值算法中有限元算法对模型进行离散分析, 化简有限元矩阵方程, 最终转化为对Ax = b高度欠定方程的求解. 首次利用分段多项式谱截断奇异值分解法处理内热源逆问题, 并对算法进行改进, 有效改善了该算法在处理多热源反演时存在的严重的热源叠加效应. 根据反演出的内热源信息, 利用有限元算法计算重构出整个模型内所有节点的温度分布. 运用数值仿真Comsol软件和具体实物实验对算法进行有效性评估, 并验证算法在不同热传导模型中的表现. 结果表明, 算法能够准确反演出多热源各参量信息, 在非均质材料模型中仍能准确地反演出热源项, 并有效重构出模型内温度场. 该算法可应用于材料无损检测及人体红外医学成像等领域.     

Effect of source strength on dislocation pileups in the presence of stress gradients

The behaviour of a dislocation pileup with a finite-strength source is investigated in the presence of various stress gradients within a continuum model where a free-dislocation region exists around the source. Expressions for dislocation density and stress field within the pileup are derived for the situation where there are first and second spatial gradients in applied stress. For a pileup configuration under an applied stress, yielding occurs when the force acting on the leading dislocations at the pileup tips reaches the obstacle strength, and at the same time, it is required that the source be at the threshold stress for dislocation production. A numerical methodology is presented to solve the underlying equations that represent the yielding conditions. The yield stress calculated for a pileup configuration is found to depend on stress gradients, obstacle spacing and source/obstacle strengths. It increases with increasing the first stress gradient, yet dependent on the second stress gradient. Furthermore, while the dependency of yield stress on the obstacle spacing intensifies with increasing the first stress gradient, it diminishes with an increase of second stress gradient. Therefore, the second stress gradient, as a newly introduced parameter, can provide a new physical insight into the size-dependent plasticity phenomena at small length scales.     

Kinetic energy spectrum and polarization of neutrons from the reaction 12C(p,n)X at 590 MeV

Abstact: The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction ¹²C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is observed which was not expected at the time the neutron beam was built. Received: 3 April 1998     

Stability of the conditions for excitation of atomic spectra in plasma produced on exposure of copper alloys to laser radiation

We show that the temperature of plasma produced by exposure of copper-zinc alloy specimens to laser radiation changes little (within the limits of random errors) with a change in the conditions of the laser effect and chemical composition of the specimens. With use of electric discharges (a low-voltage spark), systematic changes in the temperature of the plasma are observed when the chemical composition of copper-zinc alloys changes. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 319–321, May–June, 1998.     

Isotope shift and hyperfine structure measurements for 155Yb by laser ion source technique

The change in the mean square charge radius and electromagnetic moments of the neutron deficient ¹⁵⁵Yb isotope have been determined using resonance ionization spectroscopy in a laser ion source. The data point to an absence of a marked deformation change for Yb isotopes with N=84−86. Received: 2 October 1997 / Revised version: 24 October 1997