Measuring Light Field of Light Source with High Directional Resolution Using Mirrored Ball and Pinhole Camera

This paper presents a method of measuring a light field of a light source with high directional resolution using a mirrored ball and a pinhole camera. The light field describes a spatial and directional distribution of radiances from the light source. The directional distribution is expanded by a reflection on the mirrored ball, and the radiances are measured by a charge-coupled device (CCD) camera with a pinhole lens. The light source is laterally moved by a robot arm to measure the directionally expanded light field, and each pixel on a CCD can obtain the radiances from the light source through the pinhole lens with high directional resolution. The light field is estimated from the pixel value and the position of each pixel using a ray tracing technique. The light field of a krypton lamp was experimentally measured by the proposed method, and the accuracy of the measurement was evaluated against the irradiances measured by a spectro-radiometer at sample points.     

Optical Diagnostics Using a Barium Ion Beam for Spatial Resolution of Plasma Parameters

Plasma electron excitation of the 6s2S1/2 - 6p2P resonance transitions for the singly charged barium ion is proposed as an optical diagnostic for plasmas of thermonuclear interest. Spatial information arises from the intersection of a barium ion beam and the viewing optics. Measurement of relative intensity during a scan of beam and/or optics provides information for electron density and temperature profiles. Zeeman splitting of the emission lines allows local magnetic field and beta determination. Plasma and beam conditions for which such a tool is useful are given.     

非对称离子门控制方法和对离子迁移谱分辨率的改善

为了改进离子门的驱动方式,简化离子门驱动电源设计和提高离子迁移谱分辨率,通过增加一组电阻实现离子门两端的不对称供电,再对低电压端的电压进行控制实现离子门功能。分析了该方式下的两种情况对迁移管内的电场、离子迁移谱的分辨率和信噪比的影响。借助SIMION7.0对离子门两边的电场分布进行了模拟和比较,并应用数值化拉普拉斯方程的方法计算了迁移管轴线的电场数据。实验证明：相比常规迁移谱的离子门浮地驱动电源,这种驱动方法成本低,离子门电源的设计简单,能够明显提高离子迁移谱的分辨率。该方法能够应用于离子迁移谱的测量仪器或实验设备。     

The Diagnostic Probing of Laser Plasma with a Femtosecond Time Resolution Using a Three-Channel Polarization Interferometer

Physics of Atomic Nuclei - The possibility of modifying the scheme of the previously developed three-channel polarization interferometer and creating a device that allows laser probing of plasma...     

Iterative Deconvolution Algorithm for Improving Range Resolution of a CO2-Laser Based Lidar System

An iterative deconvolution algorithm for improving range resolution of long-pulse lidars is proposed, and can be applied to the lidar data obtained with the typical pulse of a CO₂-laser which consists of a gain-switching peak and a long tail. The lidar signal itself with certain temporal shift is set to be the start profile for the unknown maximally resolved profile in the proposed technique, and then is corrected in proportion to the difference between the lidar return calculated with the assumption and the real one. The same process is repeated until the correction is smaller than tolerance. Simulations are made to test the performance of the proposed algorithm. We investigate the errors in the vicinity of data boundary in the retrieved profile when a part of lidar data is absent. The sensitivity of the iteration algorithm to noise in the lidar signals and the laser pulse profile is also numerically determined.     

Ultra-High Resolution Optical Coherence Tomography (OCT) Using a Halogen Lamp as the Light Source

The axial resolution of optical coherence tomography (OCT) is determined by the coherence length of the light source. We demonstrate for the first time high-resolution OCT of biological tissue using a halogen lamp as the light source for a low coherence interferometer. High-resolution OCT imaging with 3.5 μm resolution was performed successfully for onion and porcine skin, although the coherence light power for illumination of a sample is as small as 100 nW.     

采用N2-RF等离子体氮化GaAs(001)

研究了在MBE系统中,GaAs(001)表面的氮化过程。GaAs(001)表面直接和间接地暴露在等离子体激发的N₂气流下。两种氮化过程显示了完全不同的表面氮化结果。在打开N₂发生器挡板的情况下,氮化导致GaAs(001)表面损伤,并且形成多晶结构。当增加N₂气压时,损伤变得更严重。但是,在关闭N₂发生器挡板的情况下,在500℃下,经过氮化将观察到(3×3)再构的RHEED花样,表面仍保持原子级的平整度。上述结果表明,不开N₂发生器挡板,低温(500℃下)氮化将在GaN外延生长之前形成平整的薄层c-GaN。     

机械快门对大面阵滤光片型多光谱相机成像的影响及改进

分析了大面阵滤光片型多光谱相机所用机械快门曝光时间波动对其光谱图像获取及处理造成的影响。通过对现有机械快门结构及驱动方法的研究,分析了造成该类机械快门稳定性差的原因,并提出了一种先进的机械传动方式和电路驱动方法。通过室内试验数据计算,该方案将两次曝光间的最大变化率从15.05%降低到0.96%,极大提高了曝光时间稳定性;通过外场推扫成像试验及数据处理,证明快门改进后多光谱相机所得彩色影像更接近真实目标,且无明显色彩突变。这对实际应用中多光谱相机数据处理结果的判读和目标识别具有重要意义。     

DTA模型计算高温Fe等离子体的辐射不透明度

使用DTA(detailed term accounting)模型计算了温度为20eV、密度为0.01g×cm^-3的Fe等离子体的辐射不透明度.对于处于局域热动平衡(local thermodynamic equilibrium,LTE)下的Fe等离子体,使用Saha方程计算出各价离子的丰度.使用MCHF方法得到了Fe离子的能级以及束缚-束缚跃迁的振子强度,考虑了Doppler展宽和碰撞展宽的谱线展宽机制,谱线线型采用Voigt线型.束缚-自由以及自由-自由吸收截面分别使用DCA及AA模型得到.所得的结果与美国Los Anamos National Laboratory(LANL)使用LEDCOP程序计算的结果进行了对比,两种结果符合很好.     

Si-Csl（TI）望远镜探测系统用于大动态范围空间重离子鉴别与测量的研究

太阳极轨射电望远镜（SPORT）是一颗从事太阳活动研究的卫星。重离子探测仪是其中的高能粒子探测仪的关键组成部分。鉴于重离子探测仪对多种类离子（2 ≤ Z ≤ 26）的鉴别和大范围能段（8～300 MeV/u）的测量需求,中国科学院近代物理研究所设计并研制了一套Si-CsI（Tl）望远镜探测系统样机,这套望远镜系统由1个Si探测器、1个入射面为正六边形的CsI（Tl）晶体及其专用电子学系统构成。利用兰州重离子加速器冷却储存环系统（HIRFL-CSR）提供的高品质束流对这套望远镜探测系统样机进行了在束测试,完成了种类为2 ≤ Z ≤ 18的重离子直接测量与鉴别,利用直接测量的重离子,进行外推得到,最高测量要求的300MeV/u Fe离子也在设计要求的范围内。实验结果显示这套望远镜探测器样机满足空间中对大范围能段重离子探测的设计需求,该套方案为SPORT计划中的重离子探测仪的设计及建造奠定了很好的技术基础。Solar Polar Orbit Radio Telescope (SPORT) project, aimed at solar activities and solar atmosphere, is a satellite-borne apparatus which is composed by many sub-payloads and is under development in China. High Energy Heavy Ion Telescope (HEHIT) is one of most key sub-payloads in this project, and the main purpose of HEHIT is to identify space heavy ions (2 ≤ Z ≤ 26) with a broad energy range (8～300 MeV/u). In this paper, a prototype telescope of HEHIT, which includes a silicon detector, a CsI(Tl) crystal with regular hexagonal incident plane and customized electronic system, has been developed in the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). To obtain the performance of the prototype telescope, this telescope was tested with high quality beams provided by the accelerator of Heavy Ions Facility and Cooler-Storage-Ring in Lanzhou (HIRFL-CSR). The heavy ions ranging from Z =2 to Z =18 were clearly identified and measured from the beam test and an extrapolation was also done reasonably and it showed that the prototype detector could meet the requirement of t Fe(Z =26) with energy up to 300 MeV/u. In a word, this prototype telescope could satisfy the requirements of the measured heavy ions in the future SPORT project and this scheme of telescope will provide a favorable technique in the future design and construction of HEHIT.     

Parameters of the Plasma Sheet Generated by a Sheet Beam in the Range of Forvacuum Pressures

Results of experimental investigations into the spatial distribution of the parameters of the plasma (electron concentration and temperature) generated by a sheet beam with energy up to 2 keV in argon at pressures from 6 to 9 Pa are presented. The electron beam was produced by a source with a plasma cathode specially designed for emission of beams in the range of forvacuum pressures. It is demonstrated that the character of distribution of the plasma parameters is caused by the corresponding distribution of the electron current density over the beam cross section, and the plasma parameters themselves also noticeably depend on the gas pressure and the magnetic field. A model of ionization processes that provides satisfactory agreement between the calculated and experimental dependences is suggested.     

Absorption Coefficient Measurements of Strongly Scattering Media Using Time-Resolved Transmittance of a Short Pulse in Near-Infrared (NIR) Wavelength Range

Absorption coefficient measurements of strongly scattering and weakly absorbing media have been performed using time resolved transmittance of a 100 fs pulse through a 30 mm slab containing latex spheres suspended in water and absorbing ink solutions. The scattering and absorption coefficients were selected so that the optical properties of the media were similar to those of biological tissues. Measured curves of time-resolved transmittance of the pulse through the media were used to estimate the optical properties of the media. The experiment was made at two different wavelengths, 784 nm and 810 nm. Estimated absorption coefficients were in good agreement with those measured in a nonscattering case by a spectrophotometer.Presented at the 7th International Workshop on Multiple Scattering Lidar/Light Experiments (MUSCLE7), July 21-23 1994, Chiba, Japan.     

Detection of Sea Surface Temperature (SST) Using Infrared Band Data of Advanced Very High Resolution Radiometer (AVHRR) in the Gulf of Finland

This paper presents the detection of sea surface temperature (SST) in the Gulf of Finland using infrared band data of Advanced Very High Resolution Radiometer (AVHRR). AVHRR imagery is evaluated as a main data source for monitoring SST as a measure of upwelling's dynamic. Sea surface effects (SSE), however, cause a temperature difference between the sea surface skin and water below the surface. Therefore, SSE is taken into account as one of the major error factors in the SST esimation. Further studies will be investigated using both AVHRR and MODIS in the future.     

The Sign and Micro-Origin of Complexity as Entropy (Conjectured Resolution of a Paradox)

Evolution produces ever more ordered matter, while also increasing its complexity all the time. There are various ways of measuring complexity, such as Kolmogorov's algorithmic complexity, drawn from information theory, and identified with entropy, enchancing irreversibility in harmony with the second law of thermodynamics. On the other hand, however, the creation of order should have reduced entropy; quoting Schroedinger, it represents "negentropy." To resolve this apparent contradiction we first review a similar set up (though with a totally different interaction) occurring in black holes, a model in which the physics are now explicit and fully understood at the quantum level.     

Electron Cyclotron Resonance Heating (ECRH) of a Spheromak Plasma

ECRH calculations are carried out for the MS Spheromak (Bto = 20-25 kG, ne ? 1014 cm-3) under the assumption of a straight-line ray path. These preliminary calculations indicate that for "end-on" illumination of the Spheromak plasma by an extraordinary wave at the second harmonic of the cyclotron frequency, almost complete single-pass absorption is achieved even when electron temperature is low (? 100 eV). The use of gyrotrons currently under development would make an early experimental demonstration possible.     

On the Effect of Confinement on the Structure of a Complex (Dusty) Plasma

JETP Letters - We experimentally investigate a nonlinear Hall effect for three-dimensional WTe2 and Cd3As2 single crystals, representing Weyl and Dirac semimetals, respectively. We observe finite...     

System of Solid Targets for the Production of a Wide Range of Radionuclides

Physics of Particles and Nuclei Letters - CC series cyclotrons manufactured by the JSC Efremov Research Institute of Electrophysical Apparatus (NIIEFA) are intended primarily for the production of...     

激光光场的大行程相位锁定及控制系统

提出了一种实现大行程飞秒激光脉冲对相位控制的方法。其设计思想是:在迈克耳孙干涉仪中,利用改变激光偏振态的方法改变输出两光束的光程差因子。在对He-Ne激光输出的两束光实现相位锁定的基础上,进而提出了一种可对于超短激光双脉冲相对相位差实现超大行程控制的方法。对He-Ne激光的动态相位锁定、以及飞秒激光脉冲对的相对相位差控制分别作了实验验证。对He-Ne激光的静态相位锁定结果表明干涉仪两臂光程差可以控制在纳米精度;而飞秒激光脉冲测量自相关曲线与理论拟合结果非常接近,经傅里叶变换可得到较好的单峰谱图。该系统能够在实验范围中几乎无行程限制地实现飞秒激光脉冲对的相对相位动态稳定控制。