Avalanche photodiode based detector for beam emission spectroscopy

An avalanche photodiode based (APD) detector for the visible wavelength range was developed for low light level, high frequency beam emission spectroscopy (BES) experiments in fusion plasmas. This solid state detector has higher quantum efficiency than photomultiplier tubes, and unlike normal photodiodes, it has internal gain. This paper describes the developed detector as well as the noise model of the electronic circuit. By understanding the noise sources and the amplification process, the optimal amplifier and APD reverse voltage setting can be determined, where the signal-to-noise ratio is the highest for a given photon flux. The calculations are compared to the absolute calibration results of the implemented circuit. It was found that for a certain photon flux range, relevant for BES measurements (≈10(8)-10(10)?photons/s), the new detector is superior to both photomultipliers and photodiodes, although it does not require cryogenic cooling of any component. The position of this photon flux window sensitively depends on the parameters of the actual experimental implementation (desired bandwidth, detector size, etc.) Several detector units based on these developments have been built and installed in various tokamaks. Some illustrative results are presented from the 8-channel trial BES system installed at Mega-Ampere Spherical Tokamak (MAST) and the 16-channel BES system installed at the Torus Experiment for Technology Oriented Research (TEXTOR).     

Ultra-low noise single-photon detector based on Si avalanche photodiode

We report operation and characterization of a lab-assembled single-photon detector based on commercial silicon avalanche photodiodes (PerkinElmer C30902SH, C30921SH). Dark count rate as low as 5 Hz was achieved by cooling the photodiodes down to -80 °C. While afterpulsing increased as the photodiode temperature was decreased, total afterpulse probability did not become significant due to detector's relatively long deadtime in a passively-quenched scheme. We measured photon detection efficiency >50% at 806 nm.     

Vacuum photodiode detector array for broadband UV detection in a tokamak plasma

An array of vacuum photodiode detectors has been used to monitor discharge equilibrium, stability, and cleanliness in the Macrotor tokamak. These detectors use the photoelectric effect on small tungsten plates to measure UV emission in the band lambda approximately 200-1200 angstroms, and so are sensitive mainly to impurity line radiation in Macrotor. The response of this system to controlled impurity contamination experiments and to disruptions is described. The design, construction, and background problems associated with these detectors are discussed in detail.     

An infrared interferometer for investigating subthermonuclear plasma in the GOL-3 multimirror trap

A simple Michelson CO₂ interferometer for measuring the high-temperature plasma density within one interference fringe (n _e l = 10¹⁶ cm^?2) at two points (0.8 and 9.0 m) of the long (L = 12 m) GOL-3 corrugated trap was used. A piezoelectric element that provides displacements of the mirror in the reference arm of the interferometer is used to calibrate the interferometer and perform remote control of the initial measurement phase. The interferometer is manufactured from dielectric materials, thus excluding a mechanical action of stray magnetic fields on its elements. The time resolution of the interferometer is determined by a HgCdTe diode and equals ??1 ns. The sensitivity of the interferometer is ??5 × 10^?4 of a fringe (n _e l = 2 × 10¹³ cm^?2).     

A four-segment photodiode cantilever-bending sensor for an atomic-force microscope

An electronic circuit for processing signals from a multisegment photodiode (PD) cantilever-bending sensor for an atomic-force microscope (AFM) of “classical” design is described. The electronics includes two analog channels for selecting the difference between the photocurrents of two halves of the receiving area, each channel being normalized to the signal of the total illumination of the PD. The use of modern electronic components allowed the extension of the operating frequency band of the conventional-circuit response from ordinary 200–300 kHz to 2–3 MHz, thus suppressing phase distortions in the band from 0 to 1 MHz. Owing to this, for cantilever-vibration frequencies of up to 200 kHz, the voltage at the circuit output can be accepted with a high accuracy as the signal of the instantaneous position of the cantilever tip with respect to the sample surface. It was shown that the output noise level of the proposed electronics is quite low for the reliable observation of the Brownian motion of the cantilever.     

Magnetostriction measuring device based on an optical fiber sensor with an annular photodiode

A new simple and sensitive dilatometer to measure magnetostriction of ribbons has been developed, based on an optical fiber sensor using an annular photodiode. The optical fiber is used bidirectionally, both for emission and detection of light, simplifying the access to the ribbon under test. The working principle is based on the measurement by reflection of the longitudinal displacement of the ribbon end. For a Vitroperm amorphous ribbon of 100 mm length, 21 microm thickness, and 8.3 mm width, a displacement of 2.571 microm with a maximum uncertainty of 8 nm has been obtained.     

A microwave two-wave interferometer for plasma diagnostics

The scheme and the main elements of an interferometer simultaneously operating at frequencies of the 8-and 4-mm ranges are presented. To combin e two radiations in a common waveguide section and separate them by sending to the corresponding receivers, a special separation filter has been developed. A homo-dyne technique for transferring phase measurements to an intermediate frequency is employed in the interferometer. The range of unambiguously measured phase shifts is 1.5°—360°, and the phase-shift measurement error is within 5%.     

基于四象限探测器的光束智能校正系统设计

针对工程应用中手动光束校正精度低．效率低．仪器笨重的问题,设计一套嵌入式光束自主校正系统,它利用高精度的四象限探测器检测光束偏移信号,以CPLO芯片作外围电路,DSP进行内部数据处理,再驱动步进电机控制平面摆镜,构成简单闭环回路．以此达到光束自动校正的目的．该嵌入式系统精度高,速度快,体积小,可极大地方便光束校正操作．同时由于引入新的搜索算法可以极大地提高整体系统的光束校正范围．     

A microwave interferometer for steady-state plasma density measurements

An interferometer for a wavelength of 8 mm, capable of homodyne frequency conversion for measuring the electron density of a steady-state plasma from a high-frequency ion source, is described. An original method for generating a reference intermediate-frequency signal using a cavity resonator is applied in the interferometer. The unambiguously measured phase shifts range from 1.5° to 360°, and the error in measuring the phase shift is 5%.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 98–100.Original Russian Text Copyright © 2005 by D. Nagornyi, A. Nagornyi, Voznyi.     

A fast-neutron detector based on single-crystalline silicon

It is shown that the change of the specific electrical conductivity (SEC) of silicon single crystals in the process of their irradiation is directly proportional to the fast-neutron fluence. This is used as the basis of the principle of the neutron-flux detection. The coefficient of proportionality depends on the neutron spectrum, but does not depend on the initial SEC, which significantly simplifies detector calibration. A set of wafers with different SEC values has been manufactured using the technology silicon neutron-transmutation doping. The SEC has been measured by the four-probe method. A simple method for measuring the SEC without recourse to any special setup is proposed. The random measurement error of the fast-neutron fluence was ～10%, and the absolute one was ～37%.     

基于LabVIEW的零件尺寸公差检测仪

本文设计了一种基于LabVIEW和单片机数据采集系统的机械零件尺寸公差检测仪。单片机系统采集到的传感器数据通过串口发送至PC机,LabVIEW程序接收数据并分析,将检测结果通过人机界面显示。从下位机和上位机两个部分阐述设计。测试证明,系统能实时精确地完成测量功能。     

一种基于DSP的航空相机性能检测仪电控系统研究

介绍了一种基于DSP的航空相机性能检测仪电控部分的设计和实现方法。通过设计和实验。此方法能较好的满足航空相机性能检测系统的性能要求。提高了控制精度。具有良好的应用前景。     

A generator of gas-metal plasma based on an electron-injection discharge

An earlier developed plasma generator based on a nonself-sustained gas discharge with electron injection was modernized and ensured production of gas-metal plasma and, correspondingly, multielement composite (including oxide) coatings with controlled compositions and fractional ratios of components. The characteristics of the discharge system are investigated, and the optimal ways to increase the coating-deposition rate are determined. The device developed stably operates in an oxygen atmosphere for a long service life and is characterized by the absence of a microparticle fraction.     

A thermal neutron detector based on single-crystalline silicon

It is shown that a change in the specific electrical conductivity (SEC) in silicon single crystals after irradiation and radiation defect annealing is directly proportional to the thermal neutron fluence. This fact is used as a basis of a method for measuring the neutron flux. In this case, the proportionality factor is dependent on the neutron spectrum, being independent of the initial SEC, which significantly simplifies detector calibration. In measurements of the thermal neutron fluence in terms of relative and absolute units, the rms was 4 and 8%, respectively.     

A coaxial broadband detector of high-power nanosecond microwave pulses on the hot-electron effect

The design and characteristics of a liquid-nitrogen-cooled hot-carrier detector of microwave pulses detecting electromagnetic radiation in the range 2–10 GHz with a resolution no worse than 1 ns are considered. The conversion coefficient of the voltage at the input cable into the output amplitude of a detected signal is 1.2 × 10⁻².     

基于T型衰耗器的便携式二次设备检测仪开发与应用研究

目前,在二次设备检修过程中,常用仪器有继电保护测试仪、高频电平表、电力振荡器、光功率计、光时域反射仪等,这些设备在现场实际应用中,暴露出了笨重、功能单一等缺点。该文结合现场实际,为有效解决二次设备故障问题,对二次设备检测仪器进行了开发研究,提出了便携式二次设备检测仪,阐述了便携式二次设备检测仪的基本结构和组成。该装置是一种操作简单、体积小、成本低、适用于各种不同变电站内二次设备故障查找及处理的检测装置,能够快速、有效、准确地做出判断,以达到快速处理故障的目的。     

A transition radiation detector based on thin inorganic scintillators

The possibility of designing a prototype of the scintillation transition radiation detector (Sci-TRD) based on a thin (～200 μm) inorganic scintillator has been investigated. Vacuum and silicon photomultipliers have been used in the measurements with inorganic scintillator samples based on LuBO₃:Ce and wavelength shifting fibers. The light collection coefficient has been measured for scintillator prototypes under exposure to X rays, and the quantity of photoelectrons has been experimentally determined by irradiating the Sci-TRD working substance with a ²⁴¹Am X ray source. The electron-hadron rejection ratio of the proposed Sci-TRD is expected to be ～30.     

A microwave interferometer with increased stability for diagnostics of steady-state plasma

The schematic and results of studying an interferometer for a wavelength of 8 mm with homodyne frequency conversion for measuring the electron density of a steady-state plasma are described. The design of its waveguide system allows the drift of the indicated initial phase to be reduced to a level of ±0.1°/h. The maximum phase shift measured is 360°, the tolerable signal-power decay in plasma is 16 dB, and the maximum phase measurement error is ～5%.     

基于ECPR的紫外探测器绝对光谱响应测试系统

在研制电定标热释电辐射计(electrically calibrated pyroelectric radiometer,ECPR)的基础上,设计和研制了紫外探测器绝对光谱响应测试系统.系统由紫外光源、光栅单色仪、移动探测器平台、弱信号检测仪器以及计算机和软件组成.测试采用参考探测器和待测探测器的光谱响应度比较的方法完...     

HgCdTe光伏器件多层钝化膜等离子体处理的研究

在HgCdT e光伏探测器件S iO2+ZnS复合介质膜钝化中,引入O+2清洗和A+r刻蚀两种等离子体处理工艺,大大提高薄膜附着力,成功制备出优良的光伏器件。对处理前后的样品进行场发射扫描电子显微镜扫描、原子力显微镜扫描和二次离子质谱测试后发现,O+2清洗对去除样品表面的残余光刻胶效果显著;而A r+刻蚀使ZnS表面更为粗糙,增加了成核中心,使S iO2和ZnS表面互相渗透,增强了两层介质膜的附着力。