基于局部关联信息的视频监控图像中γ辐射噪斑的消除方法

为消除γ辐射环境视频监控图像内大量形状不规则、分布无规律、能量不均衡的噪斑,提出一种利用图像局部相邻像素关联信息去除噪斑的方法。首先根据γ辐射环境视频监控图像噪斑像素值的突变特性分割噪斑区域,再利用噪斑与当前帧噪斑相邻干净区域的局部关联性及噪斑与相邻帧相同坐标干净区域像素点的局部关联性,以两个干净区域像素值为基准、像素值差值为关联度,采用步进式方法修复噪斑区域。实验结果表明,与传统的图像噪斑去除算法相比,本方法在量化指标和视觉感知上均有较大提高。该噪斑消除方法可有效去除γ辐射环境视频监控图像的噪斑,保留图像细节纹理信息。     

Measurement of the subpixel structure of AXAF CCD's

The authors present a method to measure the subpixel structure of a charge-coupled device (CCD), information necessary to accurately determine (<1% uncertainty) the absolute detection efficiency of the device. Their approach uses a thin metal film with periodically spaced holes (small, compared to the pixel size) to localize incident X-rays to a particular region of the pixel. The mesh is rotated to create a small angular misalignment between the grid holes and the CCD pixels, producing a moire effect in the data. The resultant moire pattern is compared to a CCD model, and a best fit minimization technique is used to constrain the parameters that describe the subpixel structure. This technique was developed to measure and calibrate the X-ray CCD's that will comprise one of the two focal plane instruments on-board AXAF, but it is applicable for measuring the structure of any pixelated solid state device     

基于分析晶体成像投影偏移研究

投影偏移将严重影响基于分析晶体成像系统的信息提取精度和图像质量。从基于分析晶体成像系统的原理出发,建立了光路模型,分析了产生投影偏移的主要原因,计算机模拟研究了投影偏移对折射角信息提取的影响。结果表明,投影偏移主要由分析晶体本征摇摆曲线宽度和折射角所产生。本征摇摆曲线宽度将导致相邻像素之间的射线随分析晶体的摇摆相互偏移,当样品未被射线完全覆盖时,边界像素的摇摆曲线将出现形变,虚像素将出现计数并形成畸形摇摆曲线。折射角引起的投影偏移将使摇摆曲线形状和高度发生改变,随折射角增大,出现像素错位,其影响折射角信息提取的正确性。本征摇摆曲线宽度和折射角共同产生投影偏移并影响折射角信息的提取。     

非晶硅电子射野影像装置的性能研究

使用DVS(Dosimetric verifying system)软件实现对非晶硅平板探测器的影像采集,通过分析不同辐照条件下得到的射野影像的像素值,研究非晶硅电子射野影像装置(Amorphous silicon electronic portal Imagingdevice,a-Si EPID)的辐射稳定性、剂量响应线性、照射野大小的散射影响以及不同帧时间、不同电容大小等参数设置对EPID读出信号值的影响。结果显示EPID在短期内显示出极好的稳定性,伪影增加了EPID的响应信号,减少两次照射的间隔时间或者增加两次照射剂量比例可使伪影变得更加明显。a-Si EPID具有良好的剂量线性关系,随着射野的增加散射因子也随着增加。因此只要经过适当的散射修正和剂量刻度,EPID可以作为剂量仪用来显示二维剂量分布。     

Simulation of optical model parameters with reduced model deficiency by D-optimal criterion

The nucleon optical model is widely used to calculate the elastic scattering cross-sections and polarizations. The only requirement, in using the optical model for a reliable prediction of the nuclear data is the unique set of optical model parameters (OMP). The uncertainties in the OMP lead to uncertainties in calculated cross-sections and thus the deficiency in the model itself. To our knowledge, there is no technique, to estimate the limits of variation of OMP to establish good fits with consequent reduction of optical model deficiency between these limits. In this paper, we propose D-optimal criterion and the technique of Determinant Inequalities developed by us to simulate OMP with reduced optical model deficiency. Our technique enables one to simulate the limits of variation of the OMP with the existing covariance data. The simulation of these limits would aid to establish good fits among the OMP. Further, the variation in the range of deficiency in the optical model can be ascertained well in advance. We demonstrate the utility of our technique to the OMP of ²³⁹Pu.     

A MCM-D-type module for the ATLAS pixel detector

For the ATLAS experiment at the planned Large Hadron Collider (LHC) at CERN hybrid pixel detectors are being built as innermost layers of the inner tracking detector system. Modules are the basic building blocks of the ATLAS pixel detector. A module consists of a sensor tile with an active area of 16.4 mm×60.4 mm, 16 read out ICs, each serving 24×160 pixel unit cells, a module controller chip, an optical transceiver and the local signal interconnection and power distribution busses. The dies are attached by flip-chip assembly to the sensor diodes and the local busses. In the following a module based on MCM-D technology will be discussed and prototype results will be presented     

用饱和增益开关法压缩KrF准分子激光脉冲

为提高激光作用于靶上的功率密度和耦合效率，需对目前的激光进行脉宽压缩。本工作采用饱和增益开关法，利用预放大器的放大特性对前端输出的非相干光进行了脉宽压缩，最后将脉宽为23ns的种子光压缩到了12ns，且可根据需要在5~20ns内变化。     

光纤探针方法测量界面面积浓度实验研究

采用光纤探针测量方法对垂直上升管中空气 水两相流动的界面面积浓度（IAC）分布规律进行研究。实验选用的管径为50 mm,气相、液相折算速度分别为0.01～1 m/s和0～1 m/s。通过高速摄影获取的影像数据对光纤探针法的测量精度进行评价和标定,获得IAC径向分布。利用IAC数据对几类IAC计算模型进行评价,基于截面含气率变密度模型给出平均IAC与中心截面含气率的关系式。通过与其他实验数据进行比较,表明新关系式具有较高的计算精度。     

Calculation of pixel detector capacitances through threedimensional numerical solution of the Laplace equation

A method for the solution of the three dimensional Laplace equation is presented. The method applies to planar geometry cases, such as pixel detector devices, characterized by mixed boundary conditions. Through this algorithm the capacitances associated with pixel detectors are calculated. These capacitances, which are the pixel to substrate and the interpixel capacitances, are of great importance in the design of a pixel detector since they influence the noise and the cross talk effects between pixels. Capacitances for various pixel and interpixel dimensions are presented along with an analytical approximation for the calculation of the total pixel capacitance     

The micro-imaging station of the TopoTomo beamline at the ANKA synchrotron light source

The TopoTomo bending magnet beamline at the ANKA synchrotron facility in Karlsruhe (Germany) operates in the hard X-ray regime (above 6 keV). Recently, an X-ray micro-imaging station has been installed at TopoTomo. For typical imaging applications, a filtered white beam or from 2009 on a double-multilayer monochromator is used. In order to optimize the field of view and the resolution of the available indirect pixel detectors, different optical systems have been installed, adapted, respectively, to a large field of view (macroscope) and to high spatial resolution (microscope). They can be combined with different camera systems, ranging from 14-bit dynamic range CCDs to fast CMOS cameras. The spatial resolution can be brought substantially beyond the micrometer limit by using a Bragg magnifier. Due to the moderate flux of the beamline compared to insertion-device beamlines on third generation light sources, special emphasis has been put on the efficiency of the detectors via a dedicated scintillator concept. The layout of the beamline optics makes optimal use of the coherence properties. Thus, absorption contrast, phase-contrast and analyzer-based imaging can be applied. Additionally, white beam synchrotron topography is performed, using digital indirect X-ray pixel detectors as well as X-ray film.     

Digital Architecture and Interface of the New ATLAS Pixel Front-End IC for Upgraded LHC Luminosity

A new pixel front-end integrated circuit is being developed in a 130 nm technology for use in the foreseen b-layer upgrade of the ATLAS pixel detector. Development of this chip is considered as an intermediate step towards super-LHC upgrade, and also allows having a smaller radius insertable pixel layer. The higher luminosity for which this chip is tuned implies a complete redefinition of the digital architecture logic with respect to the current ATLAS pixel front-end. The new digital architecture logic is not based on a transfer of all pixel hits to the periphery of the chip, but on local pixel logic, local pixel data storage, and a new mechanism to drain triggered hits from the double-column. An overview of the new chip will be given with particular emphasis on the new digital logic architecture and possible variations. The new interface needed to configure and operate the chip will also be described.     

Development of hybrid photon detectors with integrated siliconpixel readout for the RICH counters of LHCb

We report on the ongoing work towards a hybrid photon detector with integrated silicon pixel readout for the ring imaging Cherenkov detectors of the LHCb experiment at the Large Hadron Collider at CERN. The photon detector is based on a cross-focussed image intensifier tube geometry where the image is demagnified by a factor of 4. The anode consists of a silicon pixel array, bump-bonded to a fast, binary readout chip with matching pixel electronics. The developments and tests of full-scale prototypes with 80% active area are presented. Specific requirements for pixel front-end and readout electronics in LHCb are outlined, and recent results obtained from pixel chips applicable to hybrid photon detector design are summarized     

Optical anisotropy measurements of TRISO nuclear fuel particle cross-sections: The method

The analysis of two-modulator generalized ellipsometry microscope (2-MGEM) data to extract information on the optical anisotropy of coated particle fuel layers is discussed. Using a high resolution modification to the 2-MGEM, it is possible to obtain generalized ellipsometry images of coating layer cross-sections with a pixel size of 2.5 μm and an optical resolution of ∼4 μm. The most important parameter that can be extracted from these ellipsometry images is the diattenuation, which can be directly related to the optical anisotropy factor (OAF or OPTAF) used in previous characterization studies of tristructural isotropic (TRISO) coated particles. Because high resolution images can be obtained, the data for each coating layer contains >6000 points, allowing considerable statistical analysis. This analysis has revealed that the diattenuation of the inner pyrocarbon (IPyC) and outer pyrocarbon (OPyC) coatings varies significantly throughout the layer. The 2-MGEM data can also be used to determine the principal axis angle of the pyrocarbon layers, which is nearly perpendicular to the TRISO radius (i.e., growth direction) and corresponds to the average orientation of the graphene planes.     

偃师商城宫城建筑基址夯土的光释光测年初步研究

用光释光测年技术对河南偃师商城宫城部分宫殿和围墙基址夯土进行了定年。在夯土基址的建造过程中，有些石英颗粒可能见光而使其光释光信号被释放回零，光释光‘时钟’重新开始计时。本文用单片再生剂量法测夯土中粗颗粒石英的等效剂量，测得的等效剂量值的分布说明石英颗粒的光释光信号在基址建造过程中有不同程度的晒退。据晒退相对彻底的石英颗粒得出的夯土光释光年龄分别是4.0ka、2.2ka和2.5ka。尽管这些年龄值与考古年龄存在差异，但表明用光释法测年技术对宫殿建筑基址夯土进行定年是可行的。     

A simplified technique for shakedown limit load determination

In this paper, a simplified technique is presented to determine the shakedown limit load of a structure using the finite element method. The simplified technique determines the shakedown limit load without performing lengthy time consuming full elastic-plastic cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit load is determined by performing two analyses namely: an elastic analysis and an elastic-plastic analysis. By extracting the results of the two analyses, the shakedown limit load is determined through the calculation of the residual stresses developed within the structure. The simplified technique is applied and verified using two bench mark shakedown problems namely: the two-bar structure subjected to constant axial force and cyclic thermal loading, and the Bree cylinder subjected to constant internal pressure and cyclic high temperature variation across its wall. The results of the simplified technique showed very good correlation with the, analytically determined, Bree diagrams of both structures. In order to gain confidence in the simplified technique, the shakedown limit loads output by the simplified technique are used to perform full elastic-plastic cyclic loading simulations to check for shakedown behavior of both structures.     

Photoacoustic spectroscopy of Ni-implanted quartz

Quartz were implanted with Ni⁺ ions of various doses with energy 100 KeV. The technique of photoacoustic spectroscopy is used in the present work to investigate the optical properties of the metal implanted glass substrates. The photoacoustic technique is an absolute method, which provides a direct measurement of the energy absorbed by the sample. Here we have used a very simple technique to obtain the normalized photoacoustic spectra corrected for the spectral variation of the source in a single scan. The observed features in the photoacoustic spectrum were compared with the optical absorption data obtained from UV-Vis spectroscopy. A correlative study of the optical absorption as well as the photoacoustic spectroscopy helps to get a detailed information of the interesting physical properties of Ni⁺ nanoclusters in glass.     

X-ray detection based on complementary metal-oxide-semiconductor sensors

Complementary metal-oxide-semiconductor(CMOS) sensors can convert X-rays into detectable signals; therefore, they are powerful tools in X-ray detection applications. Herein, we explore the physics behind X-ray detection performed using CMOS sensors. X-ray measurements were obtained using a simulated positioner based on a CMOS sensor, while the X-ray energy was modified by changing the voltage, current, and radiation time. A monitoring control unit collected video data of the detected X-rays. The video images were framed and filtered to detect the effective pixel points(radiation spots).The histograms of the images prove there is a linear relationship between the pixel points and X-ray energy. The relationships between the image pixel points, voltage, and current were quantified, and the resultant correlations were observed to obey some physical laws.     

Evaluation of performance of gamma tomographic technique for correcting lump effect in radioactive waste assay

A model for estimation of the lump effect, especially for plutonium, in the tomographic technique is given, based on simulating a measurement system to assay radioactive waste drums. The results show that the tomographic technique can be successfully used for measuring heterogeneous waste drums containing lumps. When the dimensions of a pixel are chosen equal to 1 cm, the errors are not larger than 27% for a lump of plutonium metal.     

利用示踪252Cf中子源的材料鉴别技术

本文叙述了利用²⁵²Cf裂变中子源结合飞行时间技术对包裹进行无损检测的可行性研究,通过联合测量中子和伽玛射线的吸收谱确定样品的平均原子序数,完成被测材料的鉴定。实验采用自发裂变的²⁵²Cf中子源作为白中子源和伽马射线源,用塑料闪烁探测器探测中子和伽马射线。通过LabVIEW程序控制步进电机运动并整合获取的实验数据,实现了待测样品断层扫描数据采集工作的自动化。在对闪烁探测器进行能量和时间刻度后,对几种典型材料组成的样品进行实验分析,采集数据重建其分布图像,确认了用这项技术对材料无损检测的可行性。