Preparation of P-47 scintillators for STEM

Uniform P-47 powder scintillators can be prepared with reproducible mass thicknesses by sedimenting the powder in an 0·01% solution of formvar in chloroform. A reflecting coating can be glued by floating a 60 nm aluminium film on the scintillation layer in an 0·1% solution of gelatine in water. The optimum thickness of P-47 for 20–100 keV electrons increases slower than the electron range due to the absorption and scattering of light with increasing thickness. An aluminium coating increases the light output by a factor 1·85 for 20 keV and 1·4 for 100 keV electrons. The noise of the emitted light quanta and the photomultiplier detection system shows a minimum for the optimum thickness of largest light output and is only a factor 1·3–1·6 larger than the calculated shot noise of the incident electron beam.     

Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure

Measurement of x-ray emission is an important parameter to investigate runaway behavior of fast electrons produced in nanosecond-pulse gas discharge. An online detection system of x rays is described in this paper, and the system consists of an x-ray detector with NaI (Tl) scintillator and photomultiplier tube, and an integrated multichannel analyzer. The system is responsible for detecting x-ray emission signal, processing the detected signals, and scaling the energy distribution. The calibration results show that every channel of the detection system represents a given x-ray energy and various x rays can be divided into different energy ranges between 10 and 130 keV. For a repetitive nanosecond-pulse breakdown between highly nonuniform gaps in open air, an energy distribution is obtained using the online detection system. It shows that the x-ray emission is a continuous spectrum and the x rays of above 60 keV dominate in the detected energy distribution.     

Colour confocal reflection microscopy using red,green and blue lasers

To obtain colour reflected confocal images we have incorporated three lasers (HeNe: 633 nm; NdYAG: 532 nm; HeCd: 442 nm) and three photomultiplier detectors into our on-axis scanning system then adjusted the registration of the simultaneous output signals to produce full-colour images on a video monitor. Colour confocal images were produced from multi-stained fixed tissue as well as from natural pigments in fresh plant material. Rayleigh scattering properties of immunogold-labelled specimens were studied to show how variations in colour response can be utilized to identify subwavelength gold particles. Colour stereo pairs were produced to illustrate the accuracy with which the three-laser microscope system can record depth information without incurring problems due to chromatic aberration effects.     

分布式电磁接收系统多频标定信号的产生与检测

为了提高分布式电磁接收系统频域标定的效率和精度,提出了一种基于多频伪随机信号的标定方法并研究了多频标定信号的产生和标定数据的处理方法。首先,根据多频伪随机信号的解析式分析了其主频点的振幅和分布特点,通过现场可编程门阵列(FPGA)实现了伪随机信号的编码合成并产生了高精度双极性标定信号源。然后,基于相关检测的噪声抑制原理,给出了检测含噪声多频标定输出信号幅度和相位的多次相关迭代法并通过仿真进行了验证。最后,对分布式双通道电磁接收系统的采集通道和磁场传感器进行了标定测试。结果表明:在外界噪声不大于标定输出信号幅度的环境下,检测结果幅度误差小于2%,相位误差小于1°。该标定方法快速准确,可用于分布式电磁接收系统在不同野外环境下的频域标定。     

Development of multi-channel Doppler spectroscopic measurement system using 8 × 8 multianode photomultiplier tube assembly

Using an 8 × 8 channel photomultiplier tube assembly and a single Czerny-Turner monochromator, we have developed a novel Doppler spectroscopic system which can measure the time evolutions of spectral distribution of plasma emission from eight different lines of sight simultaneously. An optical lens system is employed to couple the output of the monochromator with the detector assembly, resulting in small cross-talks less than 5% in spatial distribution together with large magnification of up to 50 in wavelength direction. The suggested system yields cost-effective polychromatic measurements of eight spatial channels with uniform optical and electrical characteristics.     

三光束干涉仪参数分析及优化设计

从理想情况出发,得出了用周期为2p的光栅扫描时,由光电探测器接收到的三光束干涉光强分布式。从优化设计的角度求出了光栅的最佳参数以及干涉仪三束光的最佳光强之比;计算出了理想情况下仪器可能达到的精度以及有误差情况下的干涉条纹光强分布式;最后得出了合理的误差允差。     

Simultaneous two-dimensional laser-induced-fluorescence measurements of argon ions

Recent laser upgrades on the Hot Helicon Experiment at West Virginia University have enabled multiplexed simultaneous measurements of the ion velocity distribution function at a single location, expanding our capabilities in laser-induced fluorescence diagnostics. The laser output is split into two beams, each modulated with an optical chopper and injected perpendicular and parallel to the magnetic field. Light from the crossing point of the beams is transported to a narrow-band photomultiplier tube filtered at the fluorescence wavelength and monitored by two lock-in amplifiers, each referenced to one of the two chopper frequencies.     

A scintillation detector of pulsed soft X rays

A pulsed soft-X-ray detector consisting of a high-current photomultiplier tube and a thin-film polystyrene-based plastic scintillator was developed. Its characteristics were investigated by detecting quasimonochromatic 0.84-keV X-ray pulses. The dependence of the scintillator light output on the photon energy flux density was obtained. The average effective thickness of the surface non-scintillating (“dead”) layer affecting the spectral response of this detector type was estimated.     

电路噪声对星敏感器星点定位精度的影响

提出了一种测量星敏感器电路模块带来的图像噪声的方法。在实验室条件下,用星敏感器拍摄多幅背景图像,分析表明:不同背景图像上相同像素的灰度差值代表了电路模块带来的图像噪声,该噪声服从正态分布。模拟产生该正态分布的随机矩阵作为图像噪声加到理想的星点上,采用亚像素细分质心算法计算出带噪声的星点质心坐标,从而得到噪声带来的星点位置偏差。计算结果表明:实验室条件下,星敏感器实测6等星的质心测量精度为1/25 Pixel,而电路噪声将引起1/200 Pixel量级的标准偏差;电路噪声,尤其是DC/DC电源纹波噪声对星敏感器星点定位带来的误差是不容忽视的。     

A precision high-voltage source

A compact multipurpose regulated stabilized high-voltage (from 0 to ± 10 kV) power source for use in industrial and scientific equipment (mass spectrometers, ion optics, photomultiplier tubes, etc.) has been developed. The maximum load current is 400 μA, the noise and ripple in the output voltage are 50 mV or less, and the drift is no more than 2 × 10^?4 °C^?1. The source is the 95 × 60 × 30 mm module.     

在DDS波形发生器中相位截尾噪声的分析和抑制

直接数字频率合成技术（DDS）是近年来发展迅速的一种新的频率合成技术。全数字化的结构赋予了它很多的优点：频率转换时间短，频率分辨率很高，输出相位连续，容易集成和易编程控制等，当然也就引进了数字化结构的缺点－－输出杂散在。本文对DDS波形发生器中由于相位截尾所产生的杂散进行分析，并提出抑制相位截尾噪声的方法，给出了实现方法和实验结果。     

Multi-dimensional spectral analysis of the noise contribution from a drum washer with a dehydrating condition

Recently, there has been a growing consumer interest in the amount of noise produced by household electrical appliances. The designer of the product must determine the source of the noise, in order to eliminate the source. In the case of a household electric appliance such as the washing machine, the consumer’s complaint was about the noise that is generated during the dehydrating condition. However, in the case of the washing machine, it is difficult to identify the noise source when the washing machine uses the dehydrating condition. Several noise sources combine making it difficult to determine the key factor that contributes to the noise output. Multi-Dimensional Spectral Analysis (MDSA) is a method that can remove the correlation between different noise sources, and it expresses the key contributing factor as a unique output. This study utilized MDSA to analyze the contribution of each noise source in the output during the dehydrating condition.     

Spectroscopic measurement of ion temperature and ion velocity distributions in the flux-coil generated FRC

One aim of the flux-coil generated field reversed configuration at Tri Alpha Energy (TAE) is to establish the plasma where the ion rotational energy is greater than the ion thermal energy. To verify this, an optical diagnostic was developed to simultaneously measure the Doppler velocity-shift and line-broadening using a 0.75 m, 1800 groves/mm, spectrometer. The output spectrum is magnified and imaged onto a 16-channel photomultiplier tube (PMT) array. The individual PMT outputs are coupled to high-gain, high-frequency, transimpedance amplifiers, providing fast-time response. The Doppler spectroscopy measurements, along with a survey spectrometer and photodiode-light detector, form a suite of diagnostics that provide insights into the time evolution of the plasma-ion distribution and current when accelerated by an azimuthal-electric field.     

A Maximal Afterpulse Amplitude-to-Main Pulse Amplitude Ratio in a Photomultiplier Tube

An amplitude dependence of afterpulses caused by an ion feedback on the main pulse amplitudes in a photomultiplier tube is studied. It has been found that a maximal afterpulse amplitude-to-maximal main pulse amplitude ratio is inversely proportional to the main pulse amplitude. It has been discovered that the feedback-ion intensities are proportional to the charge released by main pulses at the output of the photomultiplier tube. These facts prove that a detection process of single ions can explain the maximal amplitudes of afterpulses.     

An Efficient High-Voltage Power Supply for a Photomultiplier Tube

An adjustable power supply for a photomultiplier tube operating in the pulsed spectrometric mode with a wide range of linearity is described. The power consumed by the source is 50 mW. The output voltage is varied from 800 to 2000 V. The maximum ripple amplitude is 2.5 mV.     

Simultaneous confocal recording of multiple fluorescent labels with improved channel separation

Confocal microscopes are often used to study specimens labelled with fluorophores. A commonly used method for simultaneous recording of the distribution of multiple fluorophores is to divide the fluorescent light emitted by the specimen into different wavelength regions using dichroic and bandpass filters. These different wavelength regions are then distributed to multiple detectors. However, the broad and overlapping spectra of commonly used fluorophores often result in considerable crosstalk between channels. A new technique, intensity-modulated multiple-beam scanning (IMS) microfluorometry, can be used to reduce this cross-talk substantially. The IMS technique is implemented with two laser beams of different wavelengths, intensity-modulated at different frequencies, which illuminate the specimen simultaneously. The two laser wavelengths predominantly excite one fluorophore each. Fluorescent light from the specimen is divided into two wavelength regions (red and green) which are detected by two photomultiplier tubes. The output signals from the photomultiplier tubes are connected to lock-in amplifiers. The effect of using modulated laser beams, in combination with lock-in amplifiers, is strongly to reduce cross-talk between the channels. The performance of the IMS technique using various types of specimen is compared with the results obtained using the conventional multi-detector method.     

A controlled stabilized high-voltage power supply for a photomultiplier tube

A small-size stabilized high-voltage power supply for a photomultiplier tube with remote digital and analog regulation of the output voltage is designed. The output voltage is smoothly regulated from 0.5 to 3 kV, the load current is 0–2 mA, and the ripple factor is 0.008%. The supply voltage is 12–16 V.     

Measuring Energy Releases in a Scintillation Detector and the Afterpulses of the Photomultiplier Tubes

A procedure for measuring energy releases in scintillation detectors by using a logarithmic RC converter in combination with a device that suppresses photomultiplier tube afterpulses is described. The total range of measured energies is 5.8 MeV to 11.6 GeV. The afterpulse suppression ratio is more than 200. The output pulse of the RC converter is synchronized with the leading edge of the anode signal from the photomultiplier tube.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 26–33.Original Russian Text Copyright © 2005 by V. Volchenko, G. Volchenko, Dzaparova, Karpov, Petkov, Yanin.     

An efficient spectroscopic detection system for cathodoluminescence mode scanning electron microscopy (SEM)

A detection system for analytical cathodoluminescence (CL) mode scanning electron microscopy (SEM) is described. This incorporates a cold stage, an efficient light collector, a monochromator and a photomultiplier and used the photon counting technique. The efficiency of the component subsystems was optimized and calibrated, and the performance of alternative light collecting and monochromating equipment is compared. The operation of the photon counter is discussed. The digital output of the photon counter was fed into a multichannel scaler and thence to a computer. This was used to correct the observed count rate with the calibrated spectral variations in the performance of the detection system. Spectra obtained at both room temperature and liquid nitrogen temperacure and monochromatic and panchromatic SEM micrographs are given as examples illustrating the value of this technique. The factors governing the performance of the system are discussed. The forms of noise in the signal and in the detection system are described and the means for minimizing, avoiding or correcting for them are dealt with. Sources of spurious signals in the SEM are treated.     

SIPM在脉冲光检测系统中的应用研究

为了实现硅光电倍增管(silicon photomultiplier,SIPM)对超出光子计数极限的微弱脉冲光信号的测量,建立了基于SIPM积分工作模式的脉冲光检测系统。测试了SIPM在同一光信号照射下,偏置电压与增益以及信噪比之间的关系,并测试了同一增益条件下,SIPM对不同光信号的响应特性。结果表明:SIPM在积分工作模式下,其增益可以达到104以上,并随着偏置电压的增加而指数增长;其信噪比也随着电压的增加而增加,在光强比较微弱的情况下,SIPM对光强是线性响应的。所设计的系统可以在一定程度上替代光电倍增管进行微弱脉冲光信号的测量。