Gas thermal conductivity sensor based on SAW

An uncoated surface acoustic wave (SAW) delay line integrated with a suitable film heater is used as a gas sensitive element based on thermal conductivity change. It detects concentrations from 0.1-100% of H₂, O₂, He, and Ar in N₂ in the temperature range from 20-150°C. The value and sign of the SAW gas response are controlled by substrate material and reference gas     

Dose Imaging Detectors for Radiotherapy Based on Gas Electron Multipliers

New techniques in charged particle therapy and widespread use of modern dynamic beam delivery systems demand new beam monitoring devices as well as accurate 2D dosimetry systems to verify the delivered dose distribution. We are developing dose imaging detectors based on gas electron multipliers (GEM) with the goal of improving dose measurement linearity, position and timing resolution, and to ultimately allow pre-treatment verification of dose distributions and dose delivery monitoring employing scanning beam technology. A prototype 10×10 cm(2) double-GEM detector has been tested in the 205 MeV proton beam using electronic and optical readout modes. Preliminary results with electronic cross-strip readout demonstrate fast response and single-pixel (4 mm) position resolution. In optical readout mode, the line spread function of the detector was found to have σ=0.7 mm. In both readout modes, the detector response was linear up to dose rates of 50 Gy/min, with adequate representation of the Bragg peak in depth-dose profile measurements.     

可燃气体检测报警器示值误差测量结果的不确定度评定

本文介绍了可燃气体检测报警器示值误差测量结果的不确定度评定.     

基于激光激发声表面波新型气体传感器的研究

提出了一种利用激光激发声表面波,通过气体吸附性薄膜对被测气体进行检测的传感原理.激光在覆有选择性气体吸附膜的铝块表面激发出声表面波,后者沿铝块表面传播.在吸附性薄膜与被测气体发生反应后,声表面波的强度被改变;然后利用PMT(光电倍增管),通过单芯光纤耦合的反射式光束偏转法探测由半导体激光器发出的探测光束,所检测的光强的变化反映了被检测气体的浓度,从而实现被测气体的浓度测量.     

硫化氢气体检测仪示值误差测量不确定度的评定

文章介绍了硫化氢气体检测仪示值误差测量不确定度的评定,并给出结果。     

Imprinted laminate wafer-level packaging for SAW ID-tags and SAW delay line sensors

We have developed a wafer-level packaging solution for surface acoustic wave devices using imprinted dry film resist (DFR). The packaging process involves the preparation of an imprinted dry film resist that is aligned and laminated to the device wafer and requires one additional lithography step to define the package outline. Two commercial dry film solutions, SU-8 and TMMF, have been evaluated. Compared with traditional ceramic packages, no detectable RF parasitics are introduced by this packaging process. At the same time, the miniature package dimensions allow for wafer-level probing. The packaging process has the great advantage that the cavity formation does not require any sacrificial layer and no liquids, and therefore prevents contamination or stiction of the packaged device. This non-hermetic packaging process is ideal for passive antenna modules using polymer technology for low-cost SAW identification (ID)-tags or lidding in low-temperature cofired ceramic (LTCC) antenna substrates for high-performance wireless sensors. This technique is also applicable to SAW filters and duplexers for module integration in cellular phones using flip-chip mounting and hermetic overcoating.     

Equivalent networks for SAW gratings

An equivalent-network approach is described for the analysis of surface-acoustic-wave gratings. Circuit parameters can be theoretically determined by applying the finite-element method to an infinite array. In this approach, all of the effects of piezoelectric perturbation, mechanical perturbation, and energy storage are taken into account. To show the validity and usefulness of this approach, examples are computed for groove and metallic gratings. Both short and open circuited metallic gratings are treated. For grooves on isotropic and Y-Z LiNbO(3) substrates, the dependence of reflection characteristics on groove depth is investigated. For aluminum strips on X-112 degrees Y LiTaO(3) 34 degrees Y-X quartz, Y-Z LiNbO(3), and 128 degrees Y -X LiNbO(3) substrates, the dependence on metallization ratio is investigated in detail.     

可燃气体检测报警器示值误差测量值的不确定度评定

介绍了可燃气体检测报警器部分检定的方法,分析了示值误差测量结果的不确定度来源,建立相应的数学模型,分别评定了各不确定度分量并进行了相对标准不确定度的合成工作,最后给出了不确定结果的报告。     

有毒有害气体检测仪示值误差测量结果不确定度的评定

本文介绍了有毒有害气体检测仪示值误差测量结果不确定度的评定,并给出结果。     

浅谈可燃气体测报仪检定工作中的问题及其解决方法

介绍了可燃气体测报仪的检定:标准气体选择,气体浓度单位换算等。     

SAW devices for consumer communication applications

An overview of surface acoustic wave (SAW) filter techniques available for different applications is given. Techniques for TV IF applications are outlined, and typical structures are presented. This is followed by a discussion of applications for SAW resonators. Low-loss devices for mobile communication systems and pager applications are examined. Tapped delay lines (matched filters) and convolvers for code-division multiaccess (CDMA) systems are also covered. Although simulation procedures are not considered, for many devices the theoretical frequency response is presented along with the measurement curve.     

Equivalent networks for SAW interdigital transducers

An equivalent network approach is described for the analysis of surface-acoustic-wave interdigital transducers. Circuit parameters can he theoretically determined by applying the finite-element method to an infinite array. In this approach, all the effects of piezoelectric perturbation, mechanical perturbation, and energy storage are taken into account, To show the validity and usefulness of this approach, examples are computed for both single- and double-electrode interdigital transducers and one-port resonators. For single- and double-electrode interdigital transducers on 128°Y-X LiNbO₃, X-112°Y LiTaO₃,₄₅°X-Z Li₂B₄O₇, and ST-X quartz substrates, the dependence of excitation characteristics on electrode thickness and metallization ratio is investigated in detail. For a 128°Y-XLiNbO ₃ substrate, frequency responses of various one-port resonators are also investigated     

Unidirectional SAW transducer for gigahertz frequencies

A single-phase unidirectional transducer (SPUDT) structure using /spl lambda//4 and wider electrodes is introduced. The considerable difference between the reflectivity of short-circuited /spl lambda//4 electrodes and that of floating /spl lambda//2-wide electrodes on 128/spl deg/ lithium niobate (LiNbO/sub 3/) is exploited. The surface acoustic wave (SAW) device operating at 2.45 GHz has critical dimensions of about 0.4 /spl mu/m, accessible for standard optical lithography.     

Squeezed States for Interferometric Gravitational-wave Detectors

Abstract

The possibility of using squeezed states for improving the shot-noise limit of the strain sensitivity of Michelson interferometers is discussed. We find that the spectrum of squeezing required depends on the method of stabilization used in the experiment. Details are given for the widely used phase-modulation technique (which also allows for recycling of the field), where we find an important application for broadband (‘two-mode’) squeezing.     

Low Temperature Detectors for Neutrino Physics

Recent years have witnessed many exciting breakthroughs in neutrino physics. The detection of neutrino oscillations has proved that neutrinos are massive particles but the assessment of their absolute mass scale is still an outstanding challenge in today particle physics and cosmology. Due to their abundance as big-bang relics, massive neutrinos strongly affect the large-scale structure and dynamics of the universe. In addition, the knowledge of the scale of neutrino masses, together with their hierarchy pattern, is invaluable to clarify the origin of fermion masses beyond the Higgs mechanism. The mass hierarchy is not the only missing piece in the puzzle. Theories of neutrino mass generation call into play Majorana neutrinos and there are experimental observations pointing to the existence of sterile neutrinos in addition to the three ones weakly interacting. Since low temperature detectors were first proposed for neutrino physics experiments in 1984, there have been impressive technical progresses: today this technique offers the high energy resolution and scalability required for leading edges and competitive experiments addressing the still open questions.     

磁轭式磁粉探伤机计量特性校准方法研究

针对磁轭式磁粉探伤机的工作原理和技术条件要求,本文提出提升力、安全性能、励磁电流、综合灵敏度验证等校准项目,对磁轭式磁粉探伤机计量特性进行讨论。     

光线示波器振子的选用

为了准确地测量记录各种被测信号，应当正确地选用振子的固有频率的阻尼，适当地选取被测信号大大小，保持信号源内阻Ｒｉ与振子的内阻ｒｇ相匹配，同时要正确地调整光点位置，以减小圆弧误差。