实验物理考核方法研究与实践

对实验物理课程教学效果的检查和评价方法进行了研究，提出了物理实验分类考核及等级证制度及具体考核方法和实施步骤，力求形成一套比较规范化的实验物理考核办法，能客观的反映出实验物理课程教学效果，促进教学改革。     

The formation of different structures in the interaction between a single femtosecond laser pulse and a thin Au film

The interactions between femtosecond (fs) laser pulses and a thin Au film deposited on a silica glass substrate were systematically investigated based on experimental data. Different structures, including microholes, nanoholes, and nanobumps, are obtained when pulses with different energies are incident on the surface of a gold film. The experimental results are discussed according to specific experimental parameters. Two physical models were constructed in order to explain the experimental results. The formation of nanoholes in a silica substrate is attributed to etching by higher order harmonic generations (HHG) when the femtosecond laser pulse interacts with the generated plasma layer, while the formation of nanobumps on the surface of an Au film is attributed to the elastic and plastic characteristics of the metal film under laser pulse irradiation.     

Investigating the temperature dependence of elastic constants by thermal fluctuation formula

The differences between the calculated values of elastic constants of materials and the experimental data are consistently restricting the application of thermal fluctuation formula to the mechanical properties of materials. In this work, the temperature dependence of elastic constants of many-body potentials is studied by thermal fluctuation formula. The differences between the calculated values and the experimental data are investigated in detail. Our studies show that the differences come from the thermal expansion of the materials: the calculated zero-stress states are bigger than the experimental zero-stress states of the materials, and this deviation makes Born terms of the thermal fluctuation formula decrease sharply as the temperature increases, while the fluctuation terms and the kinetic terms change little. As a result, the elastic constants, which are the sum of these three terms, decrease faster than the experimental data as the temperature increases. Our studies show that when the experimental zero-stress states are used as the reference states in constant volume and constant energy (NVE) simulations, the elastic constants calculated by thermal fluctuation formula are in good agreement with the experimental values.     

Quarkonium polarization in pp and p-nucleus collisions

The existing measurements of quarkonium polarization in proton-antiproton and proton-nucleus collisions are puzzling. We highlight issues which are often underestimated in the experimental analyses: the importance of the choice of the experimental acceptance on the comparison between experimental measurements and theoretical calculations. New measurements must provide more detailed information, such that physical conclusions can be derived without relying on model-dependent assumptions. We also describe a frame-invariant formalism which minimizes the dependence of the measurements on the experimental acceptance, facilitates the comparison with theoretical calculations, and probes systematic effects due to experimental biases.     

Noise-Limitations of Coherence Imaging Based on Wavefront Folding Interferometry

Noise-limitations of the coherence imaging system based on the wavefront folding interferometer are studied. The signal-to-noise ratio SNR in two kinds of noise-limiting cases, the photon-noise-limit and the detector-noise-limit, is derived and are compared with the experimental results. The experimental demonstration is conducted using a wavefront folding interferometer and a single slit that provides the light source. An ensemble of ten sets of data are measured under the same conditions and the statistics of the retrieved images are computed from them. It is verified that the experimental results generally agree with the theoretical expectations.     

Modular system for studying tonal sound excitation in resonators with heat addition and mean flow

An educational experimental system has been developed for studying tonal sound generation in acoustic resonators. Tones are excited by either heat addition or vortex shedding in the presence of mean flow. The system construction is straightforward and inexpensive. Several test arrangements and experimental data are described in this paper. The experimental setups include a modified Rijke tube, a standing-wave thermoacoustic engine, a baffled tube with mean flow, and an acoustic energy harvester with a piezoelement. Simplified mathematical models for interpreting data are discussed, and references are provided to literature with more advanced analyses. The developed system can assist both graduate and undergraduate students in understanding acoustic instabilities via conducting and analyzing interesting experiments.     

The determination of the nuclear charge distribution of 208Pb from elastic electron scattering and muonic X-rays

An iterative procedure is presented for determining a static nuclear charge distribution from experimental electron scattering cross sections and muonie atom X-ray transition energies. The errors and error correlations implied by the independent statistical errors in the experimental data are expressed in coordinate space, and kernels are derived which specify the linear constraints imposed on the charge density by the experimental data. Pseudo-experimental data for ²⁰⁸Pb, generated from a known charge distribution, are used to demonstrate the validity of the procedure. A detailed analysis of experimental data for ²⁰⁸Pb is presented, utilizing electron scattering data at five different energies and six muonic energy levels. The theoretical implications of this work concerning quantum density fluctuations and the possible existence of a central depression are discussed.     

Measurements of the Cross-sections of Produced Short-Lived Nuclei Induced by Neutrons around 14 MeV on Isotopes of Tungsten

New experimental cross-section data for the180 W(n,2 n)179 mW,186 W(n,2 n)185 mW and186 W(n,p)186 Ta reactions at the neutron energies of 13.5 and 14.4 MeV are obtained by the activation technique. The neutron beams are produced by means of the3 H(d,n)4 He reaction. The gamma activities of the product nuclei are measured by a high-resolution gamma-ray spectrometer with a coaxial high-purity germanium detector. The neutron fluence is determined using the monitor reaction93 Nb(n,2 n)92 mNb. The results in the current work are discussed and compared with the measurement results found in the literature. It is shown that these higher accuracy experimental cross-section data around the neutron energy of 14 MeV agree with some previous experimental values from the literature within experimental uncertainties.     

A full-field approach for the elastic characterization of anisotropic materials

In the paper a procedure is described whereby the characterization of isotropic and anisotropic laminae is carried out by full-field measurement of the surface rotations under proper flexural loads. The analytic formulation does not necessarily imply a numerical calibration and the elastic constants are determined by integrating the whole experimental data on the surface of the specimen. Measurements were carried out by phase-stepped speckle interferometry using a shearometer based on Michelson design. The experimental instrumentation, including the loading device, and the procedures for the manipulation of experimental data are detailedly described; experimental results obtained on a steel specimen and a composite laminate are also reported.     

Simulation of a CuBr laser in the presence and in the absence of hydrogen impurity

The generation characteristics of a CuBr laser are calculated using created model, which describes well the existing experimental data. The calculated and experimental time dependences of the atomic copper concentrations in the ground, metastable, and resonant states are compared.     

KLn Dielectronic Recombination Process of B- Through He-like Cu Ions

The KLn dielectronic recombination processes of trapped highly charged B-like through He-like Cu ions are studied theoretically, and the theoretical results are used to analyse our previous experimental data at Heidelberg electron beam ion trap （EBIT）. The theoretical resonant positions agree with the experimental resonant positions to a precision of 0.4%, in comparison with the resonant positions of those highest peaks between theory and experiment. The experimental spectra are then fitted using a formula with the theoretical resonant energies and strengths, the result shows good overall agreement between theory and experiment over a wide electron energy range. The distribution of highly charged states is obtained from the fitting parameters.     

Locally periodic Timoshenko rod: experiment and theory

The flexural vibrations of a locally periodic rod, which consists of N unit cells, are discussed both from the experimental and theoretical points of view. Timoshenko's beam theory and the transfer matrix method are used to calculate the normal-mode frequencies and amplitudes. The theoretical values are then compared with the experimental ones, which are obtained using an electromagnetic acoustic transducer (EMAT). Good agreement between the numerical results and the experimental measurements is obtained. It is shown that as N grows, a band spectrum emerges.     

A programmable electronic circuit for modelling CO2 laser dynamics

We introduce a programmable electronic circuit implementing the rich dynamics of CO2 laser models. The design and the implementation of the circuit are accomplished by using a programmable analog device, which permits an experimental characterization of the laser dynamics. The experimental results shown in the paper demonstrate that the circuit exhibits homoclinic chaos typical of CO2 laser with feedback modulation of cavity losses. Moreover, experimental results showing that noise regularizes the dynamical time scales of the system are reported.     

A quantum mechanical study of the He,H-, He-He and He-H systems

This paper applies the methods for treating diatomic molecules described in papers I and II of this series, to the interation of two normal helium atoms and the interaction of a normal helium atom and a hydrogen atom. The results are compared to the experimental results of Amdur and referred to other theoretical results where they exist. The results on the He-H interaction are in fair agreement with Amdur's experimental work. The repulsive potential of two normal helium atoms disagrees with Amdur's experimental results at the distances between 1 and 2 angstroms. The helium atom and negative hydrogen ion are also discussed.     

Mechanical characterization of polytetrafluoroethylene polymer using full-field displacement method

The aim of this work is to estimate two important material properties of the polytetrafluoroethylene (PTFE) polymer by means of a single experimental test. The displacement fields around a crack tip are used for estimating the modulus of elasticity (or, Young's modulus) and Poisson's ratio. These parameters are evaluated by fitting linear fracture mechanic expression of displacement fields in the vicinity of the crack, for mode I, to the experimental data. Measurements of these displacements are carried out using digital image correlation (DIC) method. In this way, the experimental procedure is conducted by loading a double-edge-cracked plate specimen. In order to validate the results, two available experimental tests have been performed. The modulus of elasticity is determined by means of the tensile test, using a standard test machine. Moreover, the Poisson's ratio is obtained by measuring lateral compressive and longitudinal extensional strain using DIC method.     

高功率超宽谱脉冲产生实验

 介绍了纳秒传输线充电技术的原理,利用该原理设计了高功率超宽谱脉冲产生实验装置,通过电路模拟计算分析了实验装置的工作过程。结合1.2 MV高压脉冲电源开展了实验,实验中对输出脉冲形状、输出脉冲功率和工作稳定性进行了调试,在2.7 Ω负载上获得输出功率大于30 GW,脉冲宽度1.6 ns,重复频率100 Hz。系统运行稳定,达到设计要求。     

用倍频晶体KTP实现Nd：YAG激光锁模的研究

报道用倍频晶体KTP实现Nd:YAG激光锁模的系统研究,给出了该锁模激光器输出脉宽的表达式,并和实验测量值相比较,计算值跟实验结果符合较好.文中还分析了各种参数对该锁模激光输出性能的影响.     

在非拓扑孤立子模型中核子的电磁形状因子

从Friedberg-李政道的非拓扑孤立子模型出发得到一个新的夸克禁闭势.利用这个新的禁闭势,预言了核子的静态性质,并与实验数据进行了比较.理论很好地解释了实验结果.