基于非线性最小二乘法的条纹相机标定数据处理方法

 使用基于非线性最小二乘法的方法处理扫速标定数据,获得了条纹相机的全屏扫速数据,消除了扫速非线性和空间畸变对测量结果的影响。该方法的不确定度约为0.04%,远小于条纹相机的系统误差。利用该方法得到了各个像素对应的扫速,其不确定度约为1.5%,显著减小了条纹相机测量结果的误差。     

可见光条纹相机绝对灵敏度测量

为将可见光条纹相机应用于绝对测量领域,建立了可见光条纹相机绝对灵敏度测试方法。通过对条纹相机扫描成像过程的推导,定义了条纹相机的量子效率为某一波长光入射时,输出图像净计数与输入光子数之比。使用多模光纤分束器,实现了条纹相机输入光子数的定量,用经过标定的光电倍增管监测入射光子数,建立了条纹相机量子效率测试系统。利用该系统实际测试了某条纹相机的量子效率,结果为0.7 counts/photon。对测量环节的不确定度分析表明,测试结果不确定度在5%之内。这种方法在评估Z箍缩可见光条纹相机诊断系统的灵敏度中发挥了重要作用,也可应用于其他需要确定条纹相机可见光灵敏度的场合。     

小型条纹管数值模拟及实验研究

针对无人机载及星载激光成像雷达系统对条纹管的小型化、高空间分辨率与大探测面积的应用需求,研制了一台具有高边缘空间分辨能力、高亮度增益的小型条纹相机.采用球面光电阴极、球面荧光屏技术提高了条纹相机的边缘空间分辨率和探测面积,有利于增大激光成像雷达的探测视场;采用狭缝型加速电极代替传统栅网电极,有利于提高条纹相机的电耐性和可靠性;设计了加载高达-15 kV工作电压的像缩小型条纹管,增大了条纹管的亮度增益,有助于增大激光雷达系统的探测距离.测试结果显示：在有效工作面积16 mm×2 mm内,条纹管静态空间分辨率高于29.3 lp/mm@MTF=5%（MTF表示调制传递函数）,亮度增益高达39.4.条纹相机光电阴极处静态空间分辨率高于15 lp/mm@CTF=11.64%（CTF表示对比度传递函数）;边缘动态空间分辨率高于9.8 lp/mm@CTF=5.51%;时间分辨率优于54.6 ps@T_screen=4.3 ns（T_screen为全屏时间）且在整个工作面积内具有较高的一致性;动态范围为345：1@54.6 ps.同时,为满足不同的景深及探测精度需求,相机设置六个扫描档位,可以实现不同扫速下的超快速目标诊断.该条纹相机在无人机载及星载激光成像雷达探测中具有潜在的实用价值.     

皮秒同步摄影技术的理论研究

本文主要阐述对皮秒同步摄影技术的理论研究结果。我们从大数定理出发,证明利用皮秒同步扫描相机可以获得皮秒弱光现象的真实照片。我们还利用卡逊定理和考虑了电子光学系统对空间噪声的空间滤波作用,导出了皮秒同步扫描相机的探测方程和它的最小可探测光功率密度的表达式。理论证明,皮秒同步扫描相机的最小可探测光功率密     

变像管同步扫描相机的理论分析

本文主要讨论了变像管同步扫描对皮秒弱光现象诊断理论依据,从噪声理论出发,导出了这种相机的探测方程和最小可探测光功率密度的表达式,同时用概率论和数理统计的方法研究了这种相机的极限时间分辨率,并用蒙特卡洛模拟方法计算了其时间传递函数。分析表明,该类相机的最小可探测光功率密度约为10¹²W/mm,时间分辨率较单次扫描机更高。     

相位测量偏折术中高质量条纹的获取

相位测量偏折术中的相位误差主要分为CCD相机的随机误差以及由结构光照明光源与CCD相机的非线性响应导致的非线性误差。从影响相位误差的根源分析,建立了条纹质量与相位误差、相机镜头光圈数、编码条纹的周期、调制度等因素的分析模型,并对该模型的可靠性与正确性进行仿真与实验验证。理论分析、仿真与实验结果表明:获取条纹的对比度与相机镜头光圈数、编码条纹的周期和调制度成正比,获取条纹的正弦性与相机镜头光圈数、编码条纹的周期及调制度成反比。根据该条纹质量分析模型优化系统参数,可以获得高质量的条纹。该条纹质量分析模型同样适用于面结构光三维测量等其他技术。     

DLP投影任意比特数条纹实现三维面形测量

数字光投影仪（DLP）已被广泛使用在条纹投影三维测量领域,投影条纹图的比特位深以8 bit居多,限制了可投影图案的数目与速率,也局限了三维重建的可用算法且造成相机速率冗余。为解决该问题,提出一种灵活使用比特位深的条纹投影方法,研究了不同比特数条纹图案的生成与投影方式,分析了比特数降低对条纹投影测量的影响,并总结了不同比特数下对应适用的编码测量方法和应用场景。实验从测量精度、抗噪性和抗运动模糊能力3个方面着重对比了8 bit和6 bit条纹投影方法的测量性能,证明了6 bit条纹投影方法具有编码方式灵活和重建速率快的优势。对比了6 bit和1 bit条纹投影方法的测量深度范围,发现6 bit条纹投影方法是一种高鲁棒、大景深的低速动态三维测量方案。该方法有效拓展了条纹投影方法的灵活性,充分利用了相机的冗余速率,扩大了对应三维重建可选择算法的范围,可适用于更多的基于条纹投影的三维测量系统。     

条纹变像管时间畸变的分析

应用于惯性约束核聚变和非扫描式激光雷达等的条纹变像管要求具有较大的探测面积,条纹变像管的探测面积越大,其时间畸变就越大,从而影响条纹相机的探测精度,且会导致荧光屏上成像畸变.本文计算了条纹变像管内部的电场分布,并追踪电子运行轨迹,对条纹变像管的时间畸变进行了分析.结果表明:造成条纹变像管时间畸变较大的区域是阴极到偏转板前的部分;其主要影响因素是阴极曲率半径,且阴极曲率半径存在一个最佳值使得条纹变像管的时间畸变最小,大于该最佳值,条纹变像管会产生正的时间畸变,反之,条纹变像管会产生负的时间畸变;时间畸变的绝对值随着光电子从阴极发射的初始高度的增大而增大;光电子初始能量对条纹变像管的时间畸变的影响很小.同时,模拟了不同阴极曲率半径下由于时间畸变不同导致的动态扫描狭缝像的弯曲情况,时间畸变越小,狭缝像弯曲程度越小.     

一种时间分辨三通道软X射线光谱仪

报道了时间分辨的三通道软X射线光谱仪研制工作，重点介绍了研制的三通道能谱仪的工作原理以及210 eV，420 eV和900 eV三个能区的设计参数，谱仪在上海神光Ⅱ高功率激光器三倍频实验中进行了多次实时考核，取得较好实验结果，将多道平面镜、滤光片成功配接于高时间分辨X射线条纹相机上，使该谱仪在亚千电子伏能区内，可同时进行三个波段软X射线的时间和空间分辨测量，提供的实验结果也表明：X射线平面镜结合滤光片的分光技术可应用于高时间分辨的X射线条纹相机上，从而获得高达10 ps的时间分辨. 关键词： 软X射线条纹相机 平面镜 滤光片 掠入射     

激光聚变领域高性能条纹相机研究现状与展望

条纹相机（包括X射线条纹相机和可见光光学条纹相机）是一种高时空分辨的诊断设备，在激光惯性约束聚变（ICF）物理实验研究中具有非常重要的应用。介绍了当今国内外激光聚变领域获得广泛应用的两种主要类型条纹相机的技术性能以及各自的技术特点，它们分别采用了同轴电极双聚焦电子光学扫描变像管和双板电极电子光学扫描管。在技术指标方面，重点论述了条纹相机动态范围的判据，分析了激光聚变实验对条纹相机动态范围的需求，介绍了当今国际上高性能条纹相机动态范围指标的现状。文章也介绍了和条纹相机发展应用相关的几项重要技术进展，这些进展包括先进光时标、抗辐射加固记录系统和抑制相机背景噪声的阴极选通技术。     

激光雷达探测污染气体最小浓度的估算方法

探测大气中污染气体的浓度是激光雷达的一个重要应用方面,最小可探测浓度是衡量一个雷达系统的重要指标。从测量的误差理论出发、分析得出了一般情况下．被测量最小值的估算方法：当被测量的相对误差为100％时,此时的被测量的大小就是可探测量的最小值。把此方法应用到激光雷达中来．得出了差分吸收激光雷达和拉曼雷达探测污染气体最小浓度估算公式．并把它们与已有的估算公式进行了比较,指出了原有估算公式的不足。     

On the validity of pre-equilibrium model assumptions

The Hartree-Fock calculation is performed for nuclear matter using the Skyrme interaction. It is shown that a stable density wave periodic in only one direction exists at densities below about one-third of the normal nuclear density. The critical densityρ _c below which the energy of the density wave is lower than that of the Fermi gas is determined for Skyrme interactions SKI to SKVI. It is further shown that even at densities slightly higher thanρ _c the density wave still exists as ametastable state in the sense that its energy is a local minimum in the variation parameter space. The density wave solution suddenly disappears at a higher density, since there the local minimum changes to an inflection point.     

CH_4/H_2O/CO_2在β-SiO_2(100)面吸附的第一性原理研究

多孔介质中的吸附直接影响页岩气赋存、运移.基于密度泛函理论从量子力学角度研究CH_4/H_2O/CO_2在页岩储层主体矿物成分SiO_2上的吸附构型和吸附特性,计算并分析了吸附能与态密度等特征.研究表明:CH_4、H_2O和CO_2在β-SiO_2(100)面的吸附能分布在-0.2 eV～-0.1eV区间内,为物理吸附;最小吸附能大小依次为:CH_4 H_2O CO_2,即,CO_2的吸附能力最强,H_2O次之,CH_4最弱;各吸附质处于吸附能最大与最小时的键长键角变化均小于1%,最大吸附能对应的吸附质键长键角变化率均大于吸附能最小时的,吸附质的物理结构变化微弱表明其所受作用力微弱;基底处于最稳定吸附位时态密度基本重合,表明各吸附质与β-SiO_2表面相互作用相似且差异较小;CH_4、H_2O、CO_2的态密度均出现不同程度偏移,且CO_2在能量更低的区域具有态密度分布,更易优先吸附.     

Mode II brittle fracture assessment using an energy based criterion

In this paper the minimum strain energy density criterion is modified to predict the values of mode II fracture toughness reported in the literature for several brittle and quasi-brittle materials. The experimental results are all related to mode II fracture tests performed on the semicircular bend specimen. The modified mode II fracture criterion takes into account the effect of T-stress (in addition to the singular terms of stresses/strains) when calculating the strain energy density factor at a very small critical distance from the crack tip. It is shown that the proposed criterion provides significantly better predictions for mode II fracture toughness compared with the classical minimum strain energy density criterion.     

Favourable scenarios established by SMBI for the realization of the ELMy H-mode at HL-2A

The ELMy H-mode plasmas realized with the supersonic molecular beam injection(SMBI) are studied in relation to the energy confinement and the heating power for the L–H transition(P_(L-H) ) in the HL-2A tokamak. A database is assembled for this study based on the ELMy H-mode discharges during the experimental campaigns in the period 2009–2013at the HL-2A tokamak. The statistical results show that the SMBI is favourable for reaching the H-mode by reducing the heating power at the L–H transition and for the H-mode performance by improving the energy confinement compared with the ordinary gas puffing(GP). The reduction of P_(L-H) is about 20% when the density is low, and the energy confinement enhancement factor of H_(H98y2)= τ_E/τ_(th,98y2) ≈ 1.5 is achieved with the SMBI. Note that in the database the density dependence of P_(L-H) is non-monotonic with the ˉne,min≈ 3×10~(19) m~(-3) at which the P_(L-H) is minimum. Most of P_(L-H) data are on the low density branch where the P_(L-H) increases with the decrease in density. The minimum of the P_(L-H) in HL-2A is comparable to the ITPA multi-machine threshold power scaling P_(thr■scal08). The physics behind the reduction of the P_(L-H) with the SMBI is also investigated in relation to the change of the density gradient at the plasma edge, the gas fuelling efficiency, and the recycling.     

High-sensitive terahertz detection by parametric up-conversion using nanosecond pulsed laser

A high-sensitive terahertz detector operating at room temperature was demonstrated based on parametric upconversion.A nanosecond 1064-nm Nd:YAG laser was used to pump the parametric up-conversion detector and the upconversion from terahertz wave to NIR laser was realized in a lithium niobate crystal.The minimum detectable terahertz energy of 9 p J was realized with the detection dynamic range of 54 d B,which was three orders of magnitude higher than that of commercial Golay cell.The detectable terahertz frequency range of the detection system was 0.90 Thz–1.83 THz.Besides,the effects of pump energy and effective gain length on the detection sensitivity were studied in experiment.The results showed that higher pump energy and longer effective gain length are helpful for improving the detection sensitivity of parametric up-conversion detector.     

Supersymmetron

We consider a supersymmetric model of dark energy coupled to cold dark matter: the supersymmetron. In the absence of cold dark matter, the supersymmetron converges to a supersymmetric minimum with a vanishing cosmological constant. When cold dark matter is present, the supersymmetron evolves to a matter dependent minimum where its energy density does not vanish. In the early Universe until the recent past of the Universe, the energy density of the supersymmetron is negligible compared to the cold dark matter energy density. Away from the supersymmetric minimum, the equation of state of the supersymmetron is constant and negative. When the supersymmetron reaches the neighbourhood of the supersymmetric minimum, its equation of state vanishes rapidly. This leads to an acceleration of the Universe which is transient unless supersymmetry breaking induces a pure cosmological constant and acceleration of the Universe does not end. Moreover, we find that the mass of supersymmetron is always greater than the gravitino mass. As a result, the supersymmetron generates a short ranged fifth force which evades gravitational tests. On the other hand, we find that the supersymmetron may lead to relevant effects on large scale structures.     

Printing biological solutions through laser-induced forward transfer

Laser-induced forward transfer (LIFT) is a direct-writing technique adequate for the high-resolution printing of a wide range of materials, including biological molecules. In this article, the preparation through LIFT of microarrays of droplets from a solution containing rabbit antibody immunoglobulin G (IgG) is presented. The microarrays were prepared at different laser pulse energy conditions, obtaining microdroplets with a circular and well-defined contour. The transfer process has a double threshold: a minimum energy density required to generate an impulsion on the liquid film, and a minimum pulse energy, which corresponds to the onset for material ejection. In addition, it was demonstrated that the transfer process can be correctly described through a simple model which relates the energy density threshold with the amount of released material. Finally, a fluorescence assay was carried out in which the preservation of the activity of the transferred biomolecules was demonstrated.     

A multiple-pass interferometer for electron and atom density measurements in shock tube plasmas

An eleven-pass, two-wavelength interferometer for density measurements within the ionisation relaxation region of rare-gas shock waves has been developed. The minimum detectable electron density is 1·10¹⁴ cm^?3. A method to calculate the electron temperature profile across the relaxation region from the measured density profiles is described.