Appearance potential spectroscopy with a photon counting detector and multiple scattering spectral interpretation

We describe a soft x-ray appearance potential spectroscopy apparatus, which uses a windowless hyperpure Ge detector operated in the photon counting mode. Direct comparisons of recorded spectra with the self-convolution of x-ray absorption spectra and with ab initio simulations in the multiple scattering framework are reported and discussed.     

Compensation of the shadowing error in three-dimensional imaging with a multiple detector scanning electron microscope

A method for three‐dimensional quantitative surface characterization for scanning electron microscopy is presented. The method used a quadruple scintillator detector developed by us. A surface reconstruction algorithm was performed by special software, with new algorithms for error compensation. Among these errors, detector shadowing was of particular importance. This was due to the disturbance in integration continuity when one or more detectors was screened from the flow of electrons. Several methods for the reduction of this error have been proposed and tested by us. The methods were based on software processing of complementary information, such as unshadowed detector signals, shadow depth and modified integration schemes.     

带前置放大器的热导检测器

在通用型热导检测器直流电桥的基础上 ,增加了内含倍乘× 1、× 2、× 4、× 8的前置放大器 ,使检测器的灵敏度达到 12 0 0 0 m V· m L /mg,比不加前置放大器的热导检测器的灵敏度提高了 4～ 5倍 ,已成功地应用在商品化 GC- 80 0 0 N气相气色谱仪上     

基于多最小二乘支持向量机的草酸钴粒度软测量

提出了一种基于改进的鲁棒学习方法(improved robust learning algorithm,IRLA)的多最小二乘支持向量机(multipleleast squares support vector machine,Multi-LSSVM)建模方法,用以解决非线性系统建模问题。该方法通过Bootstrap算法复制出训练集样本空间上的多个样本子空间,训练出多个成员最小二乘支持向量机模型,然后应用改进的鲁棒学习方法对成员最小二乘支持向量机模型的权重进行优化融合,从而使多最小二乘支持向量机模型具有较高的准确率和泛化能力。通过仿真实验,验证了方法的有效性;并将其应用于湿法冶金合成过程草酸钴粒度软测量建模问题,获得了比单个最小二乘支持向量机模型方法更高的预测精度。     

An image detector with space-time resolution

A block diagram and basic functional units of an image detector with space-time resolution are considered, in which the instantaneous multielement detector acts as a primary image converter. A laboratory prototype of the detector was tested as a part of the three-dimensional laser radar imager. The technical solutions used ensure parallel recording of two-dimensional and three-dimensional images. A 0.25-ns time resolution is obtained at a 4-ns width of the transmitted pulse.     

Electron imaging with Medipix2 hybrid pixel detector

The electron imaging performance of Medipix2 is described. Medipix2 is a hybrid pixel detector composed of two layers. It has a sensor layer and a layer of readout electronics, in which each 55 microm x 55 microm pixel has upper and lower energy discrimination and MHz rate counting. The sensor layer consists of a 300 microm slab of pixellated monolithic silicon and this is bonded to the readout chip. Experimental measurement of the detective quantum efficiency, DQE(0) at 120 keV shows that it can reach approximately 85% independent of electron exposure, since the detector has zero noise, and the DQE(Nyquist) can reach approximately 35% of that expected for a perfect detector (4/pi(2)). Experimental measurement of the modulation transfer function (MTF) at Nyquist resolution for 120 keV electrons using a 60 keV lower energy threshold, yields a value that is 50% of that expected for a perfect detector (2/pi). Finally, Monte Carlo simulations of electron tracks and energy deposited in adjacent pixels have been performed and used to calculate expected values for the MTF and DQE as a function of the threshold energy. The good agreement between theory and experiment allows suggestions for further improvements to be made with confidence. The present detector is already very useful for experiments that require a high DQE at very low doses.     

A magnetic-resonance detector with frequency scanning and modulation

Different variants of designing a magnetic-resonance detector on the basis of a self-excited generator (autodyne) for continuous (stationary) technique with frequency scanning and modulation were tested. The conditions for the minimum frequency dependence of the oscillation amplitude were found. The circuit diagrams of autodynes and the universal amplitude-control unit were developed. The capabilities of the developed autodynes are illustrated by magnetic-resonance spectra that were recorded at the first harmonic of the modulation frequency using the differential scan method in a zero magnetic field. Recommendations on the use of the proposed autodynes in spectrometry and magnetometry are given.     

应用CWDM实现FBG传感解调的研究

本文利用粗波分复用器（CWDM）的传输特性与波长的关系，提出了一种FBG传感解调方法并建立了实验系统。通过理论分析计算，得出系统的输入／输出之间的关系，并进行了实验验证。系统的波长解调范围为4nm左右，在没有进行光功率补偿的情况下，根据实验数据的分析计算，方差最差的情况下σmax=4pm。本系统在对分辨率要求不高的工程实际中的动态解调有着广泛的应用前景。     

自适应聚类结合迭代拟合的多圆检测算法

本文提出了一种自适应聚类结合迭代拟合新的多圆检测算法.使用自适应聚类结合迭代拟合的检测方法增强了算法鲁棒性而且避免边缘曲线连接性的要求,因此本文提出的算法对部分圆以及非连续曲线圆都具有较好的检测效果.自适应聚类操作考虑多点的分布,提高算法速度的同时避免了虚假检测的存在.最后给出的不同方法实验结果性能比较表明本文提出的算法是合理高效的,在计算机视觉领域具有一定的应用前景.     

Soft x-ray appearance potential spectroscopy with a channelplate detector

A soft x-ray appearance potential spectrometer using a channelplate detector is described and evaluated. This detector is much more sensitive than the metal photocathode in common usage and provides useful SXAPS spectra at primary electron currents of less than 10 microA. Operation of the detector at high x-ray fluxes is limited by saturation effects which can be minimized by the proper choice of channelplate and geometry.     

Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector

We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90° electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states.     

具有温度修正功能的太阳辐照度计设计

为准确获知室外自然光下太阳电池的表面辐照度,基于辐照度与太阳电池短路电流的线性关系,设计了一种适用于光伏电站的太阳辐照度计。以单晶硅电池片作为辐照度传感器,较好地解决了总辐射表由于光谱分布和辐照方位角引起的测量误差问题;利用热敏电阻器采集电池片温度,为辐照度测量值增加了温度修正功能,提高了辐照度计的准确性;采用脉冲式太阳模拟器校准辐照度计,最后在室外自然光下与标准太阳电池测试比对,获得了误差仅为1.5%的较好结果。     

Contrast in confocal scanning microscopy with a finite detector

The optical properties of a general scanning microscope are determined within the framework of Fourier imaging theory. For a simple model optical system, with Gaussian lens and detector apertures, the contrast transfer function can be expressed in terms of elementary functions. The theory predicts that spatial resolution and depth discrimination vary continuously with detector aperture and that defocus phase contrast is present in transmission images obtained with a symmetric objective, collector lens confocal microscope.     

A high-speed miniature screening gaschromatograph with flame ionization detector

The combination of Gas chromatography (GC) for separation and Flame Ionization Detection (FID) for detection and identification of the components of a mixture of compounds is a fast and strongly proved method of analytic chemistry. The objective of this research was to design a combined High-speed miniature screening Gas chromatograph along with a Flame Ionization Detector for quick, quantitative and qualitative analysis of gas components. This combined GC-FID system is suitable to detect the volatile and semi-volatile hydrocarbons present in a gas mixture. The construction made it less expensive, easy to use and movable. The complete gas path was developed. On/off valves, temperature and flow sensors and their interface electronics were used for controlling purpose. A Microcontroller was programmed to measure the temperature and gas flow using the sensors and to control and regulate them using the electronics and valves. A pocket PC with its touch screen served as a user interface for the system. Software was developed for the pocket PC, which makes the communication possible with the Microcontroller. The system parameters can be indicated in the Pocket PC as simple text and also the analysis result can be displayed.     

Detection of charged particles with charge injection devices

A method for using charge injection devices (CIDs) for detection of high-energy charged particles from inertial-confinement fusion reactions is described. Because of the relatively small depletion region of the CID camera (depletion depth of approximately 7 mum), aluminum foils are placed in front of the device to reduce the energy of the charged particles and maximize the energy deposited in the CID. Simultaneous measurements of (2)H(d,p)(3)H protons with a CID and a surface barrier detector indicate that the CID is an efficient detector of charged fusion products. Tests using high energy alpha particles emitted from a radium-226 source are also reported.     

Absorbance and fluorometric sensing with capillary wells microplates

Detection and readout from small volume assays in microplates are a challenge. The capillary wells microplate approach [Ng et al., Appl. Phys. Lett. 93, 174105 (2008)] offers strong advantages in small liquid volume management. An adapted design is described and shown here to be able to detect, in a nonimaging manner, fluorescence and absorbance assays minus the error often associated with meniscus forming at the air-liquid interface. The presence of bubbles in liquid samples residing in microplate wells can cause inaccuracies. Pipetting errors, if not adequately managed, can result in misleading data and wrong interpretations of assay results; particularly in the context of high throughput screening. We show that the adapted design is also able to detect for bubbles and pipetting errors during actual assay runs to ensure accuracy in screening.     

Five-element Johann-type x-ray emission spectrometer with a single-photon-counting pixel detector

A Johann-type spectrometer with five spherically bent crystals and a pixel detector was constructed for a range of hard x-ray photon-in photon-out synchrotron techniques, covering a Bragg-angle range of 60°-88°. The spectrometer provides a sub emission line width energy resolution from sub-eV to a few eV and precise energy calibration, better than 1.5 eV for the full range of Bragg angles. The use of a pixel detector allows fast and easy optimization of the signal-to-background ratio. A concentration detection limit below 0.4 wt% was reached at the Cu Kα(1) line. The spectrometer is designed as a modular mobile device for easy integration in a multi-purpose hard x-ray synchrotron beamline, such as the SuperXAS beamline at the Swiss Light Source.     

Linear Induction Accelerators with Magnetic Elements

A new class of linear induction accelerators with magnetic elements used as the sources of electron beams for relativistic high-power microwave generators is presented [1, 2]. Such accelerators have been under development at the Nuclear Physics Institute of Tomsk Polytechnical University (NPI TPU) since the 1990s on the basis of an original configuration with the use of low-impedance strip forming limes laid over the induction system as an Archimed helix [4]. By now, the designed accelerators have electron energies of 0.4–2.4 MeV at currents of 2–6 kA and pulse repetition rates of up to 400 Hz in the continuous operation mode and up to 3.3 kHz in the pulse-burst mode.     

Spectral-domain phase microscopy with improved sensitivity using two-dimensional detector arrays

In this work we demonstrate the use of two-dimensional detectors to improve the signal-to-noise ratio (SNR) and sensitivity in spectral-domain phase microscopy for subnanometer accuracy measurements. We show that an increase in SNR can be obtained, from 82 dB to 105 dB, using 150 pixel lines of a low-cost CCD camera as compared to a single line, to compute an averaged axial scan. In optimal mechanical conditions, phase stability as small as 92 μrad, corresponding to 6 pm displacement accuracy, could be obtained. We also experimentally demonstrate the benefit of spatial-averaging in terms of the reduction of signal fading due to an axially moving sample. The applications of the improved system are illustrated by imaging live cells in culture.