Laser-produced plasma helium-like titanium Kα x-ray source and its application to Rayleigh-Taylor instability study

Several experiments are performed on the ShenGuang-II laser facility to investigate an x-ray source and test radiography concepts.X-ray lines emitted from laser-produced plasmas are the most practical means of generating these high intensity sources.By using a time-integrated space-resolved keV spectroscope and pinhole camera,potential helium-like titanium Kα x-ray backlighting (radiography) line source is studied as a function of laser wavelength,ratio of pre-pulse intensity to main pulse intensity,and laser intensity (from 7.25 to～11.3×10 15 W/cm 2).One-dimensional radiography using a grid consisting of 5 μm Au wires on 16 μm period and the pinhole-assisted point projection is tested.The measurements show that the size of the helium-like titanium Kα source from a simple foil target is larger than 100 μm,and relative x-ray line emission conversion efficiency ξ x from the incident laser light energy to heliumlike titanium K-shell spectrum increases significantly with pre-pulse intensity increasing,increases rapidly with laser wavelength decreasing,and increases moderately with main laser intensity increasing.It is also found that a gold gird foils can reach an imaging resolution better than 5-μm featured with high contrast.It is further demonstrated that the pinhole-assisted point projection at such a level will be a novel two-dimensional imaging diagnostic technique for inertial confinement fusion experiments.     

Microstructure and strain films using in-plane grazing analysis of GaN epitaxial incidence x-ray diffraction

This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.     

Investigation of the topological shape of bovine serum albumin in solution by small-angle x-ray scattering at Beijing synchrotron radiation facility

This paper reports that at a newly constructed small-angle x-ray scattering station of Beijing Synchrotron Radia- tion Facility, the topological shape of ligand-free bovine serum albumin in solution has been investigated. An appropriate scattering curve is obtained and the calculated value of the gyration radius is 31.2~=t=0.25 ~_ （11=0.1 nm） which is co- incident with other ones＇ results. It finds that the low-resolution structure models obtained by making use of ab initio reconstruction methods are fitting the crystal structure of human serum albumin very well. All of these results perform the potential of the beamline to apply to structural biology studies. The characteristics, the defects, and the improving measures of the station in future are also discussed.     

一种基因芯片光学扫描图像倾斜校正方法研究

针对在基因芯片光学扫描时产生的图像倾斜问题,提出了一种基于像素灰度的芯片图像倾斜校正方法。结合基因芯片图像的结构特点,基于行、列方向像素灰度定义芯片图像的校正指标。在角度检测范围内,利用折半搜索方法,基于校正指标来检测芯片图像的校正角度和芯片图像的校正位置。实验结果表明,该方法能有效地检测多类基因芯片图像的倾斜角度,具有较强的鲁棒性和实用性。     

Investigation of fast of runaway electrons pitch angle scattering in the EAST tokamak

This paper reports that an experimental investigation of fast pitch angle scattering （FPAS） of runaway electrons in the EAST tokamak has been performed. From the newly developed infrared detector （HgCdTe） diagnostic system, the infrared synchrotron radiation emitted by relativistic electrons can be obtained as a function of time. The FPAS is analysed by means of the infrared detector diagnostic system and the other correlative diagnostic systems （including electron-cyclotron emission, hard x-ray, neutrons）. It is found that the intensity of infrared synchrotron radiation and the electron-cyclotron emission signal increase rapidly at the time of FPAS because of the fast increase of pitch angle and the perpendicular velocity of the energetic runaway electrons. The Parail and Pogutse instability is a possible mechanism for the FPAS.     

Non-contact angle measurement based on parallel multiplex laser feedback interferometry

We present a novel precise angle measurement scheme based on parallel multiplex laser feedback interferometry （PLFI）, which outputs two parallel laser beams and thus their displacement difference reflects the angle variation of the target. Due to its ultrahigh sensitivity to the feedback light, PLFI realizes the direct non-contact measurement of non- cooperative targets. Experimental results show that PLFI has an accuracy of 8＂ within a range of 1400＂. The yaw of a guide is also measured and the experimental results agree with those of the dual-frequency laser interferometer Agilent 5529A.     

Interference Angle on Quantum Rotational Energy Transfer in Na＋Na2 （A1 ∑u^＋,v=8-b^3∏0u,v=14） Molecular Collision System

In order to study the collisional quantum interference （CQI） on rotational energy transfer in atom-diatom system, we have studied the relation of the integral interference angle and differential interference angle in Naq-Na2 （A1 ∑u^＋,v=8-b^3∏0u,v=14） collision system. In this paper, based on the first-Born approximation of timedependent perturbation theory and taking into accounts the anisotropic effect of Lennard-Jones interaction potentials, we present a theoretical model of collisional quantum interference in intramolecular rotational energy transfer, and a relationship between differential and integral interference angles.     

Small angle X-ray scattering of the colloidal crystal

The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and devel- oping the various applications of colloidal crystal. Small-angle X-ray scattering （SAXS） technique was used to obtain the bulk structure of the colloidal crystal at Beamline lW2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.     

Can a non-unitary effect be prominent in neutrino oscillation measurements?

Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to parameterize it. A quasi-unitary factor △QF is defined to be measured in neutrino oscillation exper-iments and the numerical results show that the improvement in experimental precision may help us figure out the secret of neutrino mixing.     

低能Cl^-在Al2O3绝缘微孔膜中的输运过程

研究了10 keV Cl^-离子穿越Al2O3绝缘微孔膜的物理过程,发现穿越的Cl^-其分布中心在初束中心即0°附近,Cl^-离子穿透率下降与几何穿透一致,这是典型的直接几何穿越有一定角发散的微孔导致的结果;而出射的Cl0和Cl^+以微孔轴向为中心分布,Cl^+和Cl0穿透率下降慢于几何穿透.模拟计算发现沉积电荷会使出射粒子中Cl^-占主要成分,并使出射Cl^-角分布中心移动到微孔轴向方向而随微孔膜倾角移动;而在不考虑沉积电荷的情况下,计算结果较好地符合了实验结果.通过分析在不同倾角下散射过程对出射粒子的角分布和电荷态分布的影响,发现绝大部分的Cl0是通过一次和两次散射出射的,其中一次散射出射的Cl0占主要成分,从而导致出射的Cl0沿微孔轴向出射而Cl^+主要是经过一次碰撞出射.这导致了随倾角增大,出射的Cl0穿透率下降速度比Cl^+小,Cl0所占比例相对增大较快,从而导致观测到的Cl^+/Cl0的比例下降.本文结果更仔细地描述了低能离子穿越绝缘体微孔的物理机理,印证了之前实验和理论工作的结果,发现在10 keV以上能区的Cl^-离子穿越绝缘微孔膜的过程中,沉积电荷并未起到主要作用,其主要穿透特征是散射过程造成的.     

Combined Influence of Off-diagonal System Tensors and Potential Valley Returning of Optimal Path

The two-dimensional barrier passage is studied in the framework of Langevin statistical reactive dynamics. The optimal incident angle for a particle diffusing in the dissipative non-orthogonal environment with various strengths of coupling between the two degrees of freedom is systematically calculated. The optimal diffusion path of the particle in a non-Ohmic damping system is revealed to have a probability to return to the potential valley under the combined influence of the off-diagonal system tensors.     

Rapid roughening in thin film growth of an organic semiconductor (diindenoperylene)

The scaling exponents alpha, beta, and 1/z in thin films of the organic molecule diindenoperylene deposited on SiO2 under UHV conditions are determined. Atomic-force microscopy, x-ray reflectivity, and diffuse x-ray scattering were employed. The surface width displays power law scaling over more than 2 orders of magnitude in film thickness. We obtained alpha = 0.684+/-0.06, beta = 0.748+/-0.05, and 1/zeta = 0.92+/-0.20. The derived exponents point to an unusually rapid growth of vertical roughness and lateral correlations. We suggest that they could be related to lateral inhomogeneities arising from the formation of grain boundaries between tilt domains in the early stages of growth.     

Characterization of the N-polar GaN film grown on C-plane sapphire and misoriented C-plane sapphire substrates by MOCVD

Gallium nitride (GaN) thin film of the nitrogen polarity (N-polar) was grown on C-plane sapphire and misoriented C-plane sapphire substrates respectively by metal-organic chemical vapor deposition (MOCVD). The misorientation angle is off-axis from C-plane toward M-plane of the substrates, and the angle is 2° and 4° respectively. The nitrogen polarity was confirmed by examining the images of the scanning electron microscope before and after the wet etching in potassium hydroxide (KOH) solution. The morphology was studied by the optical microscope and atomic force microscope. The crystalline quality was characterized by the x-ray diffraction. The lateral coherence length, the tilt angle, the vertical coherence length, and the vertical lattice-strain were acquired using the pseudo-Voigt function to fit the x-ray diffraction curves and then calculating with four empirical formulae. The lateral coherence length increases with the misorientation angle, because higher step density and shorter distance between adjacent steps can lead to larger lateral coherence length. The tilt angle increases with the misorientation angle, which means that the misoriented substrate can degrade the identity of crystal orientation of the N-polar GaN film. The vertical lattice-strain decreases with the misorientation angle. The vertical coherence length does not change a lot as the misorientation angle increases and this value of all samples is close to the nominal thickness of the N-polar GaN layer. This study helps to understand the influence of the misorientation angle of misoriented C-plane sapphire on the morphology, the crystalline quality, and the microstructure of N-polar GaN films.     

Tilt-induced localization and delocalization in the second Landau level

We have investigated the behavior of electronic phases of the second Landau level under tilted magnetic fields. The fractional quantum Hall liquids at nu=2+1/5 and 2+4/5 and the solid phases at nu=2.30, 2.44, 2.57, and 2.70 are quickly destroyed with tilt. This behavior can be interpreted as a tilt driven localization of the 2+1/5 and 2+4/5 fractional quantum Hall liquids and a delocalization through the melting of solid phases in the top Landau level, respectively. The evolution towards the classical Hall gas of the solid phases is suggestive of antiferromagnetic ordering.     

基于IMU的3D扫描仪倾角标定方法北大核心CSCD

3D扫描仪以精度高、速度快、自动处理、稳定性好等优势在场景三维重建、智能制造、自动驾驶、虚拟现实等领域得到了广泛的应用。目前3D扫描仪设备多是安装在三脚架上,容易因为地面不平使得扫描仪的转轴和重力方向产生夹角,最终导致拍摄出的全景图和点云倾斜,成为影响三维重建精度的关键难题。针对该问题,提出一种借助惯性测量单元标定3D扫描仪倾角的方法。该方法利用惯性测量单元输出的加速度信息,通过一个面阵相机建立惯性测量单元和3D扫描仪的联系,将惯性测量单元的加速度信息转到扫描仪的转轴上。利用该信息计算出扫描仪转轴与重力方向的夹角,并将该倾角补偿到生成的全景图和点云中,校正倾斜模型。通过实验对校正前后计算的角度进行对比,实验结果证明倾角测量误差可以控制在0.5°以内。并且经过标定后,精度至少提升20%,验证了整个标定方法的可靠性和准确性。     

RExPr1-xP5O14晶体生长及其光谱

水热法生长了RExPr1-xP5O14单品,RE=La,Ce,Nd,Eu,Gd,Yb,Tm,Y,(x=0.1)单晶的最大线度为2cm。我们研究了原料的合成,观察了吸收,荧光,红外光谱,并计算了22400～16380cm-1范围内的Pr3+离子的振子强度。热重分析观察到在867～930℃有弱的分解。X射线衍射分析指出:结构为单斜晶系,空间群为P21/C;晶胞参数为a=8.73Å,b=9.04Å,c=13.02Å,β=90.5°     

HL-2M 装置环向场线圈中心轴倾角测量方法

通过测量HL-2M 装置环向场线圈指形接头及斜面接头上的若干个点的空间坐标,利用点到平面的距离最小二乘原则,对环向场线圈的外轮廓平面进行拟合。再利用各外轮廓平面与中心轴的空间位置关系,求解得出环向场线圈中心轴倾角。通过简化模型及数值模拟求解出在不同的空间点坐标测量标准差情况下的中心轴倾角。在空间点三维坐标低测量标准差的情况下(σ=0.05mm),拟合求得倾角的相对误差为0.10‰,相对标准偏差为 1.21‰。     

30 keV He~(2+)在不同倾斜角度的聚碳酸酯微孔膜中的传输过程

本文测量了30 keV的He~(2+)入射倾斜角度分别为-0.5~?,-1~?,-1.5~?和-2.5~?的聚碳酸酯纳米微孔膜后,出射粒子角度分布、电荷态分布以及相对穿透率随时间的演化.当微孔膜倾斜角度在-0.5~?,-1~?和-1.5~?时,出射的He~(2+)离子始终保持在入射束流方向,出射的He~0原子出射方向由微孔孔道方向逐渐转移到入射束流方向,在实验过程中观测到明显的电荷交换,这一现象与之前发现的导向效应不同,微孔内部沉积的电荷斑和微孔内表面原子的短程集体散射作用,克服入射离子的横向动量,使入射离子在微孔内表面以上以类似镜面掠射的方式出射,并发生时间演化效应,主要传输机制为电荷斑辅助的表面以上的类似镜面掠射行为.而当倾斜角度在-2.5~?时,出射的He~(2+)离子始终保持在入射束流方向,出射的He~0原子始终保持在微孔孔道方向,沉积的电荷斑很难克服入射离子的横向动量,没有时间演化效应,主要传输机制为微孔内表面以下的多次随机非弹性碰撞过程.这一物理图像使中能离子入射不同倾斜角度的微孔膜物理认识更加深入和完整.     

Optimizing head/media electrical characterization in the presence of skew at high track density

The skew angle causes a discrepancy in determining the reader-to-writer offset (RWO) when using different periodical patterns in track profile tests. It also separates the peak overwrite (OW) from the peak high frequency amplitude HFA, (1 T periodical pattern) on corresponding track profiles. Furthermore, higher track density and larger skew angle exacerbate the skew effect and induce more RWO error, thus impacting the parametric performance optimization. Simulation studies are used to interpret the skew effect on the RWO determination and OW cross-track characteristics. Based on experimental investigations and simulation analyses, using the HFA, track profile for deriving the optimal RWO is proposed for spin-stand tests. Actual parametric characterization has proven that the optimal RWO minimized the skew effect and the RWO error, thus improving the parametric performance and reducing the test variation. The method is beneficial and necessary for the high track density characterization.     

Tunable repetition frequency passively Q-switched Tm,Ho:YLF laser with Cr:ZnS as a saturable absorber

We first report a tunable repetition frequency passively Q-switched 2053 nm Tm,Ho:YLF laser by tuning the tilt angle of the Cr:ZnS saturable absorber. When the pump power is 1.4 W, the pulse repetition frequency can be tuned from 1.6 to 19.4 kHz by changing the position of Cr²⁺:ZnS saturable absorber along the cavity axis. When the Cr²⁺:ZnS saturable absorber is near the Tm,Ho:YLF crystal, the repetition frequency can be tuned from 0.8 to 4.0 kHz by changing the tilt angle of the Cr²⁺:ZnS saturable absorber, furthermore, the pulse width and the pulse energy are near constants of 1.7 μs and 3.5 μJ, respectively.