Development and research of a laser photo-acoustic SF<Subscript>6</Subscript> gas analyzer

An analysis of various optical schemes for the development of a laser SF₆ gas analyzer based on a CO₂ laser operating in free-running mode and a resonant photo-acoustic detector (PAD) is presented. The use of a sealed gas-filled cell to normalize PAD signals on the absorbed power in the cell is suggested. Compensation for the influence of the tuning of the CO₂ laser wavelength near 10.6 μm on measured SF₆ concentration is possible. The results of experimental studies of a laser photo-acoustic SF₆ gas analyzer at various concentrations, including in the air flow, are presented. It is shown experimentally that the relative measurement error of the SF₆ concentration due to the instability of the laser radiation wavelength does not exceed 5% in the range from ~80 ppb to 40 ppm. The limit of the sensitivity of the developed gas analyzer was ~1 ppb SF₆.     

Reducing the Energy Consumption of a Laser Photo-Acoustic SF<Subscript>6</Subscript> Gas Analyzer

Experimental studies of the operating modes of a laser photo-acoustic SF₆ gas analyzer that were aimed at reducing its energy consumption were carried out. It was shown in the experiments that an average power of CO₂ laser radiation of at least 100 mW is required for the assured detection of low SF₆ concentrations (less than 100 ppb). To reduce the energy consumption of the gas analyzer, it is proposed to decrease the repetition frequency of CO₂ laser pulses by several times and operate on subharmonics of the resonance frequency of the photo-acoustic detector. The experimental results made it possible to reduce the energy consumption of the gas analyzer to ~15 V A and use a Li-ion battery from a laptop to power it. The duration of the continuous operation of the gas analyzer on one battery charge was at least 6 h.     

Emitters based on semiconductor Bragg microcavities

This paper presents a brief review of the progress in the development of two types of semiconductor emitters based on semiconductor Bragg microcavities. The first type of these emitters is a vertical-cavity laser based on Al _x Ga_1−x As. The laser demonstrates stable single-mode lasing at a wavelength of 795 nm, which opens prospects for its use in miniature atomic frequency standards on the basis of Rb⁸⁷. The second type is a single-photon emitter based on semiconductor quantum dots. The design of such an emitter was developed on the basis of a semiconductor Bragg microcavity providing a high level of external quantum efficiency of the emitter (up to 80%) and high performance due to the Purcell effect.     

Simultaneous measurement of CO and CO2 at elevated temperatures by diode laser wavelength modulated spectroscopy

One single semiconductor distributed-feedback (DFB) laser is used to demonstrate the possibility of simultaneous measurements of CO and CO₂ at elevated temperatures. Wavelength modulation spectroscopy with second-harmonic detection is used to improve the detection sensitivity and accuracy. The concentrations of CO and CO₂ are determined from the WMS-1-normalized absorption-based WMS-2f signal peak heights of a proper line pair of CO and CO₂ near 6357.814 cm⁻¹ and 6357.312 cm⁻¹, which are selected using some line-selection criterions for the target temperature range of 300–1000 K. The CO and CO₂ concentrations measurements are within 2.86% and 2.69% of the expected values over the tested temperature range 300–1000 K. The minimum detectable concentrations of CO and CO₂ at 1000 K are 250 ppm m and 280 ppm m respectively.     

单层MoS2和WS2的太赫兹近场显微成像研究

采用太赫兹散射式扫描近场光学显微镜(THz s-SNOM)研究了化学气相沉积法制备的单层MoS₂和WS₂晶粒的太赫兹近场响应。在没有可见光激发时,未探测到可分辨的太赫兹近场响应,说明晶粒具有较低的掺杂载流子浓度。有可见光激发时,由于光生载流子的太赫兹近场响应,能够测得与晶粒轮廓完全吻合的太赫兹近场显微图。在相同的光激发条件下,MoS₂的太赫兹近场响应强于WS₂,反映了两者之间载流子浓度或迁移率的差异。研究结果表明,THz s-SNOM兼具超高的空间分辨率和对光生载流子的灵敏探测能力,对二维半导体材料和器件光电特性的微观机理研究具有独特的优势。     

A silicon position-sensitive detector of charged particles and radiations on the basis of functionally integrated structures with nano-micron active regions

A novel pixel array two-coordinate detector with internal amplification is described. Linear amplification of the primary ionization current is attained by using functionally integrated structures of a p-i-n diode and a bipolar transistor in the detector pixel. It is shown that a 16-fold decrease (from 0.64 to 0.04 μm²) in the emitter area of the functionally integrated structures allows the current gain of pixel bipolar structures to be increased from 10 to 80 at a pixel collector current of ∼1 nA. As a result, it is possible to obtain spectra of radiations weakly interacting with the silicon (e.g., γ rays) and to reduce the response time of the position-sensitive detectors by an order of magnitude, down to 100 ns and less. It is demonstrated that the detector can be used in fast position-sensitive detection of particles with time, coordinate, and energy resolutions of ≤100 ns, ≤25 μm, and ≤12%, respectively.     

Wire GEM detector

A wire GEM (WGEM) detector with a gas gap between meshes was constructed. The detector provides the amplification 5 × 10⁴ for the gas mixture of Ar + 20% CO₂ at atmospheric pressure. As compared with well-known GEM detectors produced by perforation the plastic plate metallized on both sides the WGEM does not suffer from breakdowns between its electrodes and the effect of accumulation of charges on holes’ walls is absent. As a result the WGEM has high reliability and stability.     

A detector for imaging of explosions on a synchrotron radiation beam

Synchrotron radiation (SR) offers a unique chance to study the structure of a substance in fast processes. Since SR is emitted by electron bunches in a storage ring, the SR burst corresponding to a single bunch may be very short. Should a detector capable of detecting SR from a single bunch without mixing signals from different bunches be available, it is possible to obtain information on changes in the state of the material in a sample under investigation with a very high time resolution. A detector for imaging of explosions on an SR beam—DIMEX—has been developed by the Budker Institute of Nuclear Physics (Siberian Division of the Russian Academy of Sciences, Novosibirsk). This detector is a high-pressure ion-ization chamber with a strip readout at a pitch of 0.1 mm. The electron component of primary ionization is collected within 50 ns, which is substantially shorter than the orbital period of a bunch in the VEPP-3 storage ring (250 ns). The DIMEX is filled with a Xe—CO₂ mixture (3: 1) at an absolute pressure of 7 atm. The spatial resolution of the detector is ∼210 μm, and its efficiency for radiation with an energy of 20 keV is ≥50%. The dynamic range of the detector is ∼100, which allows one to measure the signal with an accuracy of ∼1%. In this case, the maximum flux of X-ray photons, at which the DIMEX operates in a linear region, is ∼10¹⁰ photons/(channel s). Today, the detector has been used in experiments aimed at studying evolution of the density in detonation waves and processes of nanoparticle production at the VEPP-3 storage ring by employing the small-angle X-ray scattering technique.     

Gap-free lap welding of zinc-coated steel using pulsed CO2 laser

CO₂ laser welding of zinc-coated steel sheets in the lap configuration has been a major research effort for the automotive industry for many years. The introduction of a gap between the sheets is one way of solving the zinc gas explosion problem. However, this requires sophisticated clamping devices and spacer materials. A homogeneous gap is therefore difficult to realise in high volume production. This paper describes a simple but useful approach for CO₂ laser welding of zinc-coated steel sheets in the lap configuration. By using a gated pulse mode, a seam welding process is developed that allows zinc-coated materials to be welded in a gap-free, overlap configuration. Laser seam welds in the lap configuration were produced in 0.7 mm-thick steel sheet with 7 μm zinc coating on both sides. A number of pulsed CO₂ laser welding parameters, including peak power, duty cycle, travel speed, pulse repetition rate, and pulse energy, were identified. Furthermore, the effects of pulsed CO₂ laser welding parameters on weldability were also investigated. The study shows that through the proper selection of welding parameters, it is possible to produce visually sound welds where porosity is still unavoidably formed. It was observed that decreasing the welding speed could reduce the porosity within the visually sound welds.     

PET探测器的现状及发展趋势

正电子放射层析技术（ＰＥＴ）是科学研究强有力的工具,文中综述了ＰＥＴ探测器的研究状况,并着重介绍了深度检出型探测器和基于半导体器件的探测器研究的最新进展。     

NO2 chemiluminescent emission from flames influenced by acoustic noise

The effect of acoustic noise on combustion is investigated from the perspective of NO_x emissions. A robust, plug-in probe that exploits the natural emission signal from the combustion gases, and which can have practical relevance, is used. Acoustically pulsed flames are stabilized on aburner, and NO₂ chemiluminescence is measured with an intensified detector at various frequencies. The results indicate the NO₂ emission increases in noisy flames at certain frequencies more significantly than others. Noise at higher frequencies in the range 0.8≈1 kHz effects the nitrogen chemistry in stoichiometric flames (ϕ=1), but not that in lean flames (ϕ-0.7 and 0.8).     

Experimental study on heat transfer characteristics of internal heat exchangers for CO2 system under cooling condition

This paper presents the heat transfer characteristics of the internal heat exchanger (IHX) for CO₂ heat pump system. The influence on the IHX length, the mass flow rate, the shape of IHX, the operating condition, and the oil concentration was investigated under a cooling condition. Four kinds of IHX with a coaxial type and a micro-channel type, a mass flow meter, a pump, and a measurement system. With increasing of the IHX length, the capacity, the effectiveness, and the pressure drop increased. For the mass flow rate, the capacity of micro-channel IHX are higher about 2 times than those of coaxial IHX. The pressure drop was larger at cold-side than at hot-side. In the transcritical CO₂ cycle, system performance is very sensitive to the IHX design. Design parameters are closely related with the capacity and the pressure drop of CO₂ heat pump system. Along the operating condition, the performance of CO₂ IHXs is different remarkably. For oil concentration 1, 3, 5%, the capacity decreases and the pressure drop increased, as compared with oil concentration 0%. This paper was recommended for publication in revised form by Associate Editor Yong Tae Kang Prof. Young-Chul Kwon received his B.S. degree in Precision Mechanical Engineering from Pusan National University, Korea, in 1989. He then received his M.S. and Ph.D. degrees from POSTECH, in 1991 and 1996, respectively. Dr. Kwon is currently a Professor at the Division of Mechanical Engineering at Sunmoon University in Chungnam, Korea. He serves as a chief of the Institute of Automation and Energy Technology. Dr. Kwon’s research interests include heat exchanger, CO₂ cycle, heat pump, and energy recovery ventilator for HVAC&R. Mr. Dae-Hoon Kim is currently Doctoral student at the Mechanical Engineering from Hanyang University in Seoul, Korea. His research topics include experimental and numerical of CO₂ heatpump system. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Prof. Jae-Heon Lee received his B.S. degree in Mechanical Engineering from Seoul National University, Korea, in 1971. He then received his M.S. and Ph. D. degree from Seoul National University in 1977 and 1980, respectively. Dr. Lee is currently a Professor at the school of Mechanical Engineering at Hanyang University in Seoul, Korea. Dr. Lee is currently a president at the Korea Institute research interests include simulation of thermal fluid and Plant engineering and construction. Dr. Jun-Young Choi received his B.S. degree in Mechanical Engineering from Yonsei University, Republic of Korea, in 1989. He then received his M.S. and Ph. D. degrees from Yonsei University in 1991 and 1999, respectively. Dr. Choi is currently a chief researcher with the 18 years experience on the energy performance testing of HVAC/R product. He is now assigned to the Energy Technology Center at Basic Industry Division at Korea Testing Laboratory. He has been involved in the development of Design and Manufacturing Technology for Air-Conditioner E.E.R. and Performance Testing Equipment for Cooling and Heating System with Non-CFCs, and natural refrigerants. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Dr. Sang Jae Lee received his Ph.D. degree in Mechanical Engineering from Hanyang University, KOREA, in 2008. Dr. Lee is currently a Researcher at the Korea Institute of Industrial Technology in Cheonan, Korea. Dr. Lee’s research interests CO₂ heatpump system, liquid desiccant air conditioning system and Micro heat exchanger.     

基于非分散红外(NDIR)原理的煤矿甲烷检测仪

介绍了一种基于非分散红外(NDIR)原理的煤矿甲烷检测仪的总体设计。该检测仪使用进口红外检测元件,以新型电调制光源代替机械调制光源,实现了对煤矿井下大范围甲烷浓度的实时测量、液晶显示和超限声光报警等功能,并把甲烷浓度值转化为与煤矿其他设备兼容的4~20 mA标准模拟电信号,最后给出该检测仪在甲烷体积分数为0~10%的测量结果。     

采用 CCD 器件的半导体材料应力测试仪的研制

研究和实现了采用面阵CCD器件的半导体材料应力测试仪。介绍了测量原理,设计完成了相应的光学测量系统、硬件控制系统和控制测量所需的软件。最后介绍了对硅上SiO₂、Si₃N_{4膜应力实际测量的结果。}     

Tribological behaviors and mechanisms of Ti<Subscript>3</Subscript>AlC<Subscript>2</Subscript>

Tribological behaviors and the relevant mechanism of a highly pure polycrystalline bulk Ti₃AlC₂ sliding dryly against a low carbon steel disk were investigated. The tribological tests were carried out using a block-on-disk type high-speed friction tester, at the sliding speeds of 20–60 m/s under a normal pressure of 0.8 MPa. The results showed that the friction coefficient is as low as 0.1∼0.14 and the wear rate of Ti₃AlC₂ is only (2.3–2.5) × 10⁻⁶ mm³/Nm in the sliding speed range of 20–60 m/s. Such unusual friction and wear properties were confirmed to be dependant dominantly upon the presence of a frictional oxide film consisting of amorphous Ti, Al, and Fe oxides on the friction surfaces. The oxide film is in a fused state during the sliding friction at a fused temperature of 238–324 °C, so it takes a significant self-lubricating effect.     

太赫兹光致力近场显微成像技术及应用研究

设计并搭建了太赫兹光致力显微成像系统(THz PiFM),首次在太赫兹波段实现了近场光力纳米显微成像测量。该系统基于原子力显微镜,利用探针对所受力的灵敏检测能力,通过探测探针与样品之间近场偶极相互作用产生的光场梯度力,实现无探测器的太赫兹近场显微成像。利用该系统,对可见光激发下的单层MoS₂晶粒进行了近场纳米显微成像表征,并分析了晶粒边缘近场光力信号增强的机制。研究结果表明,THz PiFM对二维材料中的载流子具有高灵敏的探测能力。与传统的太赫兹近场显微成像技术相比,THz PiFM无需太赫兹探测器,而且可获得更加优越的空间分辨率和成像信噪比,是一种低成本、高性能的新型太赫兹近场显微成像技术。     

激光粒度仪的技术发展与展望

激光粒度仪是一种应用广泛的粒度测量仪器。本文介绍了激光粒度仪的测量原理,对激光粒度仪的技术发展包括光路系统的设计与优化、探测器及其他方面的改进作了概述。仪器的光学结构对其性能具有决定性的影响,光学结构的优化主要是为了扩展仪器的测量下限;采用不同的探测器则可以保证仪器的高重现性和全量程的高分辨率。文章最后展望了激光粒度仪的发展方向。     

Flow measurement challenges for carbon capture,utilisation and storage

Carbon Capture, Utilisation and Storage (CCUS) is a key element in the United Kingdom Government strategy for reducing carbon dioxide (CO₂) emissions. The UK aims to capture and store 10 million tonnes of CO₂ each year by 2030.At each stage in the CCUS infrastructure, accurate measurement of the CO₂ flow rate is required, over a range of temperatures, pressures, flow rates and fluid phases, where the flow measurement must be validated through a credible traceability chain. The traceability chain provides the underpinning confidence required to verify meter performance, financial and fiscal transactions, and environmental compliance. The UK equivalent of the EU Emissions Trading System (EU ETS) specifies a maximum uncertainty value for CO₂ flow measurement. Accordingly, the provision of accurate and traceable flow measurement of CO₂ is a prerequisite for an operational CCUS scheme.However, there are currently no CO₂ flow measurement facilities, nationally or internationally, providing traceable flow calibrations of gas phase, liquid/dense phase and supercritical phase CO₂ that replicate real-world CCUS conditions. This lack of traceable CO₂ gas and liquid flow measurement facilities and associated flow measurement standards is a significant barrier to the successful implementation of CCUS projects worldwide.This paper presents an overview of the traceability chain required for CO₂ flow measurement in the UK and globally. Current challenges are described along with potential solutions and opportunities for the flow measurement community.     

A neutron semiconductor detector based on TIInSe<Subscript>2</Subscript>

A new semiconductor detector of neutron radiation based on a TIInSe₂ crystal has been investigated. The detector is produced from a homogeneous semiconductor sample with two electric contacts and operates in an integrating mode. It is shown that, owing to its high sensitivity (～10^?13 A/(neutron cm^?2 s^?1)) and small size (the volume of the sensitive crystal element is ～7 mm³), the detector is capable of monitoring spatial, time, and intensity distributions of γ rays and neutrons in pulse research reactors.     

A Simple,Low Cost,Fast Galvanostat

Abstract

In this work, two spectrometric methods are described to have a noiseless β energy spectrum of radiocarbon (¹⁴C) as low‐energy β emitter. The spectrometers use two timing techniques with a silicon (Si) surface barrier semiconductor detector. The experimental results are compared; they show that the methods followed in the present work were successful for obtaining a noiseless β energy spectrum.