光学薄膜测量时平顶光束激励的表面热透镜理论模型

推导了调制的平顶光束激励下基于Fresnel衍射积分的表面热透镜理论，通过数值模拟，比较了平顶光束和高斯光束激励下样品内部温度场、表面形变场和探测光衍射信号的径向分布，分析了影响表面热透镜信号的实验参数.结果表明，在最佳探测位置，平顶光束激励下的表面热透镜系统比相同情况下高斯光束激励下的灵敏度高，最高时约2倍，更有利于薄膜吸收测量. 关键词： 表面热透镜 光学薄膜 平顶光束     

A Beta Beam complex based on the machine upgrades for the LHC

The beta beam CERN design is based on the present LHC injection complex and its physics reach is mainly limited by the maximum rigidity of the SPS. In fact, some of the scenarios for the machine upgrades of the LHC, particularly the construction of a fast cycling 1 TeV injector (“Super-SPS”), are very synergic with the construction of a higher γ beta beam. At the energies that can be reached by this machine, we demonstrate that dense calorimeters can already be used for the detection of ν at the far location. Even at moderate masses (40 kton) as the ones imposed by the use of existing underground halls at Gran Sasso, the CP reach is very large for any value of θ₁₃ that would provide evidence of ν_e appearance at T2K or NOνA (θ₁₃≥3°). Exploitation of matter effects at the CERN to Gran Sasso distance provides sensitivity to the neutrino mass hierarchy in significant areas of the θ₁₃-δ plane. PACS 14.60.Pq; 14.60.Lm     

Large-angle production of charged pions by 3?GeV/c–12?GeV/c protons on carbon, copper and tin targets

A measurement of the double-differential π^± production cross-section in proton–carbon, proton–copper and proton–tin collisions in the range of pion momentum 100 MeV/c≤p<800 MeV/c and angle 0.35 rad≤θ<2.15 rad is presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was done using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d²σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). PACS 13.75.Cs; 13.85.Ni     

单光束扩束扫描激光周视探测系统参数对探测能力的影响

针对现有单光束激光同步扫描周视探测对脉冲重复频率要求较高,难以实际应用的问题,提出单光束扩束扫描激光周视探测方法.基于单光束扩束扫描激光周视探测工作原理,推导了最低扫描频率和脉冲频率解析式;分析了圆柱目标回波特性及关键参数截面衰减系数,建立了脉冲扩束激光圆柱目标回波功率数学模型,讨论了系统参数对截面衰减系数的影响,得到最大相邻脉冲光束夹角表达式;重点分析了脉冲频率、光束角和光束入射角对不同直径目标的探测能力的影响;得到了探测系统对典型条件下最大光束角、最低脉冲频率的计算方法.结果表明,对扫描光束稍加扩束可有效降低脉冲重复频率要求.研究结果可为单光束脉冲激光周视探测系统设计、优化提供理论依据.     

C2GT: intercepting CERN neutrinos to Gran Sasso in the Gulf of Taranto to measure θ13

Today’s greatest challenge in accelerator-based neutrino physics is to measure the mixing angle θ₁₃ which is known to be much smaller than the solar mixing angle θ₁₂ and the atmospheric mixing angle θ₂₃. A non-zero value of the angle θ₁₃ is a prerequisite for observing CP violation in neutrino mixing. In this paper, we discuss a deep-sea neutrino experiment with 1.5 Mt fiducial target mass in the Gulf of Taranto with the prime objective of measuring θ₁₃. The detector is exposed to the CERN neutrino beam to Gran Sasso in off-axis geometry. Monochromatic muon neutrinos of ≈ 800 MeV energy are the dominant beam component. Neutrinos are detected through quasi-elastic, charged-current reactions in sea water; electrons and muons are detected in a large-surface, ring-imaging Cherenkov detector. The profile of the seabed in the Gulf of Taranto allows for a moveable experiment at variable distances from CERN, starting at 1100 km. From the oscillatory pattern of the disappearance of muon neutrinos, the experiment will measure sin²θ₂₃ and especially Δm² ₂₃ with high precision. The appearance of electron neutrinos will be observed with a sensitivity to P(ν_μ→ν_e) as small as 0.0035 (90% CL) and sin²θ₁₃ as small as 0.0019 (90% CL; for a CP phase angle δ=0° and for normal neutrino mass hierarchy).     

Large-angle production of charged pions by 3-12.9?GeV/c protons on beryllium, aluminium and lead targets

Measurements of the double-differential π^± production cross-section in the range of momentum 100 MeV/c≤p< 800 MeV/c and angle 0.35 rad ≤θ<  2.15 rad in proton–beryllium, proton–aluminium and proton–lead collisions are presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross-sections d²σ/dpdθ at six incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c, 8.9 GeV/c (Be only), 12 GeV/c and 12.9 GeV/c (Al only)) and compared to previously available data.     

Channeling of charged particles in crystals as an effective tool for studying Mo-Re alloys

The crystal structure of Mo-Re alloys is investigated by channeling of helium ions at an energy of 1.8 MeV in the concentration range in which the electronic topological transition was previously revealed from an analysis of the superconducting and normal properties. It is found that, for Mo-Re alloys containing 11 and 32 at. % Re, the dependences of the yield Y of backscattered particles on the angle θ between the particle beam and the 〈110〉 crystallographic direction exhibit a specific feature in the form of an additional maximum at the half-width (θ = 0.8°). It is assumed that the observed feature is associated with the formation of a superstructure due to the electronic topological transition in Mo-Re alloys.     

双压电片变形镜像差校正能力

利用实测影响函数,通过数值仿真分析了有效孔径、光束入射角度对于20单元双压电片变形镜像差校正能力的影响。仿真结果表明:有效孔径为16 mm时,变形镜对于各阶像差的校正能力较好;而随着光束入射到变形镜角度的增大,变形镜对于像差的校正精度与校正幅度都会出现下降,但是如果能够将入射角控制在25以内,入射角度对变形镜的像差校正能力影响不大。     

Displacements and deformations of a vortex light beam produced by the diffraction grating with embedded phase singularity

Properties of vortex light beams produced by a diffraction grating with groove bifurcation (“fork” structure) are studied in the case of small diffraction angles. Analytical expressions are derived for the amplitude distribution of a diffracted beam generated from an incident Gaussian beam with arbitrary radius and wavefront curvature, transversely shifted and inclined with respect to the nominal axis (normal to the grating crossing it at the bifurcation point). In such situations, the output beam becomes asymmetric; the optical vortex core and the intensity maximum displace orthogonally to the incident beam shift direction. The nearest vicinity of the vortex core preserves its circular symmetry and the optical vortex remains locally isotropic. The effects of misalignment depend on the incident beam characteristics, the diffraction order and the propagation distance behind the grating. Experimental measurements support the results of calculations.     

Measurement of the production of charged pions by protons on a tantalum target

A measurement of the double-differential cross-section for the production of charged pions in proton–tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment (100 MeV/c ≤p< 800 MeV/c and 0.35 rad ≤θ< 2.15 rad) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d²σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). In addition, the pion yields within the acceptance of typical neutrino factory designs are shown as a function of beam momentum. The measurement of these yields within a single experiment eliminates most systematic errors in the comparison between rates at different beam momenta and between positive and negative pion production. PACS 13.75.Cs; 13.85.Ni     

Mechanism of structural changes of Si(111) surfaces subjected to low-energy ion pulses during molecular-beam epitaxy

Reflected high-energy electron diffraction (RHEED) and detection of the intensity oscillations of the specular reflection have been used to investigate morphological changes in Si(111) associated with the two-dimensional layer-by-layer mechanism of silicon growth from a molecular beam under conditions of pulsed (0.25–1 s) bombardment with low-energy (80–150 eV) Kr ions in the interval of small total radiative fluxes (10¹¹–10¹² cm²²), for which the density of radiation-generated defects is small in comparison with the surface density of the atoms. After pulsed ion bombardment an increase in the intensity of the specular reflection is observed if the degree of filling of the monolayer satisfies 0.5<θ<1. No increase in the intensity occurs during the initial stages of filling of the monolayer. The maximum amplitude increment of the oscillations is reached at θ≈0.8. The magnitude of the amplitude increment of the RHEED oscillations increases with temperature up to 400°C and then falls. At temperatures above 500°C amplification of the reflection intensity essentially vanishes. Experiments on multiple ion bombardment of each growing layer showed that the magnitude of the amplitude increment of the oscillations decreased as a function of the number of deposited layers (the order of the RHEED oscillation). A mechanism for the observed phenomena is proposed, based on the concept of surface reconstruction by pulsed ion bombardment accompanied by formation of a (7×7) superstructure, which corresponds to a decrease of the activation energy of surface diffusion of the adatoms. Within the framework of the proposed mechanism the results of Monte Carlo modeling agree with the main experimental data. Zh. éksp. Teor. Fiz. 114, 2055–2064 (December 1998)     

晶体几何结构及入射角度对自抽运相位共轭特性影响的研究

基于两块不同尺寸的Cu∶KNSBN晶体自抽运相位共轭实验,研究了光折变晶体的几何结构及入射角度对自抽运相位共轭特性的影响,得到在入射位置不变化的情况下,随着入射角度的变化相位共轭光输出有最大值,几何结构不同对应的最大值不同。并从理论上分析了晶体结构及入射角度在双作用区自抽运相位共轭机理中的作用,指出几何结构、入射角度与自抽运光通道、耦合系数的关系,及在自抽运相位共轭效应中存在一个最佳入射角度,这时相位共轭光输出最大。最后,对理论上的相位共轭反射率公式进行了修正。对自抽运相位共轭实际应用中,选择最佳入射角度提供了理论和实验依据。     

Influence of the plate inclination angle on rivulet formation and breakdown of non-isothermal liquid film

The influence of the plate inclination angle relative to the horizon on a distance between formed rivulets and breakdown of a falling water film was studied experimentally on a heater of 150×150 mm. Dependences of the distance between rivulets on the heat flux density and plate inclination angle were examined. In experiments two zones of influence of the heat flux on a distance between rivulets were revealed: at θ ≥ 20° distances between the rivulets do not depend on the heat flux, and at θ ≤ 15° they decrease with a rise of the heat flux. Data on film breakdown were generalized with consideration of evaporation effect. It is shown that there is almost no effect of inclination angle on film breakdown in the whole range of studied Reynolds numbers. The work was financially supported by the President of RF (No. NSh-6749.2006.8), Russian Foundation for Basic Research (Grants Nos. 05-08-33325-a, 06-01-00360-a) and SB RAS (Interdisciplinary integration project No. 111).     

STABILITY OF BRIGHT SCREENING-PHOTOVOLTAIC SPATIAL SOLITONS

We present a theoretical analysis of the stability of screening-photovoltaic (SP) spatial solitons in biased photovoltaic-photorefractive materials in the case of neglecting the loss of the material and the effect of diffusion. When an incident optical beam is a SP soliton, this beam propagates along a linear path with its shape kept unchanged. When the maximum amplitude, width and functional form of an incident optical beam are slightly different from those of a SP soliton, the beam reshapes itself and tries to evolve into a solitary wave after a short distance. That is, these SP solitons are stable against small perturbations. However, optical beams that significantly differ from SP soliton solutions tend to experience larger cycles of compression and expansion, and their maximum amplitudes oscillate with propagation distances. The larger the perturbations, the stronger the oscillation.     

平行光束反射光强调制型光纤位移传感器研究

讨论并建立了一种基于平行光束发射光强调制的光纤位移传感器，该传感器的入射和接收光纤的端部都用渐变折射率光纤（GRIN）制成的透镜耦合，入射光纤的渐变折射率光纤透镜发出的平行光束以一定入射角照射到试件表面，接收渐变折射率光纤透镜放置在入射光的镜面反射方向，详细分析了试件表面为镜面反射和朗伯反射时传感器的输出特性，由仿真计算可知，通过调整测头的结构参量，该传感器可获得较强的输出信号，适用于对测量范围和工作点有灵活要求的场合。     

Accurate method for determining tilt bias angles in thin films of nematic liquid crystals

We have developed a new method for measuring tilt bias angles in spatially uniform and nonuniform thin films of nematic liquid crystals. The method employs modulation ellipsometry, based on the use of an exponentially decaying light wave to probe the boundary layer. Oscillations of the director of the liquid crystal, which are induced by the flexoelectric torque, are excited with an external periodic field. A periodic variation of the ellipticity of the light wave reflected from the interface is detected at both the first and second harmonics of the exciting electric field. When these two Fourier components of the electrooptic response are known, it is possible to calculate both the tilt bias angle θ₀ of the director and the dynamic deviation δ₀ of the tilt bias angle. The angles θ₀ and δ₀ measured by this method on the surface of an electrode (ITO) and on the surface of a ferroelectric film (a copolymer of vinylidene fluoride and trifluoroethylene), oriented in a corona discharge, were equal to θ ₀=5.1°, δθ=0.5° and θ₀=89°, δθ=0.06°, respectively. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 387–392 (25 March 1998)     

远距离探测拉曼光谱特性

为了发展远距离探测未知或危险物质的方法, 设计并建立了近同轴可见光远距离拉曼光谱探测实验装置, 对硝酸盐固体样品进行了距离为2-10 m的拉曼光谱测量, 初步研究了拉曼信号强度与激发光功率、探测距离、样品浓度及样品表面方向之间的关系. 实验观察到三种硝酸盐在1050 cm^-1附近的拉曼谱线, 其微小的差异可作为识别特征. 硝酸铵的特征拉曼谱线强度正比于激发光功率, 近似平方关系; 与探测距离之间趋向于二次反比关系; 与样品浓度接近指数关系; 与样品表面朝向有近似余弦函数的关系.     

大气湍流对多抖动法相干合成技术中相位调制信号的影响

分析了大气湍流对采用多抖动法实现的相干合成阵列光束中相位调制信号的影响. 文章首先根据广义惠更斯-菲涅耳原理,采用折射率结构函数对大气湍流进行描述,推导了多抖动法相干合成中阵列光束通过大气湍流后相位调制信号的一般表达式. 在此基础上进行数值模拟,分析了传输距离、湍流强度、光束阵列占空比和光斑尺寸等因素对相位调制信号的影响. 研究发现随着传输距离的增大,相位调制信号强度会先增大后减小,存在一个极大值点;随着湍流强度的增强,相位调制信号强度极大值点的出现距离不断缩短;当光束阵列占空比一定时,随着光斑尺寸的增大 关键词： 大气湍流 相干合成 多抖动法 相位调制     

Propagation dynamics and experimental observation of quadratic vortex beam

The concept of a quadratic vortex beam is proposed, in which phase term of the beam is given by exp(i mθ²). The phase of the quadratic vortex beam increases with azimuthal angle nonlinearly. This change in phase produces several unexpected effects. Unlike the circularly symmetric beam spot of normal vortex beams, the intensity distribution of the quadratic vortex beam is shown to be asymmetric. The phase singularities will shift in the transverse beam plane on propagation.     

Prediction of sound transmission loss through multilayered panels by using Gaussian distribution of directional incident energy

In this study, a new prediction method is suggested for sound transmission loss (STL) of multilayered panels of infinite extent. Conventional methods such as random or field incidence approach often given significant discrepancies in predicting STL of multilayered panels when compared with the experiments. In this paper, appropriate directional distributions of incident energy to predict the STL of multilayered panels are proposed. In order to find a weighting function to represent the directional distribution of incident energy on the wall in a reverberation chamber, numerical simulations by using a ray-tracing technique are carried out. Simulation results reveal that the directional distribution can be approximately expressed by the Gaussian distribution function in terms of the angle of incidence. The Gaussian function is applied to predict the STL of various multilayered panel configurations as well as single panels. The compared results between the measurement and the prediction show good agreements, which validate the proposed Gaussian function approach.