Quartz strip resonators as a temperature sensor.

The miniature frequency-temperature sensor in the form of a small quartz strip vibrating in the thickness-shear mode with the resonant frequency in the range from 4 to 8 MHz is considered. Y-cut strips rotated in the range from 0 degrees to 27 degrees are the subject of the study. The temperature coefficients of the resonance frequency for the different rotation angles are given. The different temperature dependence of the resonant frequency of the quartz temperature sensors vibrating on the fundamental and harmonic frequency of the thickness-shear modes is pointed out.     

红外碳硫传感器信噪比改善方法研究

应用于钢铁、矿物等检测的红外碳硫仪的研制在国内的研究还存在诸多问题,由于其在红外检测中位于一个非常敏感的区域,国内高精度红外碳硫传感器的研究迫切需要迈上新台阶。其检出限和检测精度要达到国际先进水平还存在传感器的气室工艺不够、探测器与光源的资源限制、信号的调制方式落后等问题。当然也存在信号的前期滤波、信号后期处理方面的原因。本文针对当前红外碳硫传感器的研究现状,对改善信噪比的方法进行探究和分析,并提出了相应的解决措施和具体思路。     

Application of the nitroanisole as an infrared detector used in middle infrared interferometer

We propose the application of nitroanisole as a detector for middle infrared (mid-IR) interferometry or holography. The present experiment utilizes the liquid form of nitroanisole, which has a thermal lens effect, i.e. a temperature dependent refractive index. Since the nitroanisole absorbs IR radiation as heat, it is possible to estimate the IR intensity distribution on the nitroanisole from the diffraction pattern made by visible laser light that is transmitted through the nitroanisole. In this study, the time resolution and the diffraction efficiency of the nitroanisole was measured under various conditions. The experimental results show that the nitroanisole has a time resolution as high as that of a standard video camera, as well as a high diffraction efficiency and the spatial resolution equivalent to that of a conventional IR camera. Furthermore, we confirmed that the phase shift in mid-IR region can be estimated by analyzing the change in the visible diffraction pattern.     

Accurate measurement of pressure

This paper briefly describes the fundamental principles of the instruments used for accurate measurement of hydrostatic pressure and in particular the use of piston gauges as primary pressure standards. Different methods for the calibration of secondary standards have been discussed and in particular, emphasis has been given to the calibration of secondary piston gauges against the primary standards by the cross-float method along with the evaluation of uncertainties attached to different correction factors associated with the measurement of pressure from these gauges. The importance of secondary pressure standards in the region 0.1 GPa to several GPa has also been defined.     

Morphological center operator for enhancing small target obtained by infrared imaging sensor

Infrared small target in image obtained by infrared imaging sensor is usually different from the surrounding regions, which is the important region in infrared image for different applications. However, the infrared small target is dim and embedded in clutter background, which makes the small target difficult to be detected or recognized. So, it is important to enhance infrared small target. Morphological center operator could smooth important image features, which may be well used for infrared small target enhancement. To well enhance infrared small target, a morphological center operator based method is proposed. The morphological center operator is specified to suppress most of the background of the infrared image through the strategy of feature extraction. Then, the infrared small target is well enhanced. Experimental results show that, the proposed method performs well for enhancing infrared small target and the performance is better than some other methods. So, the proposed method could further improve the performance of infrared imaging sensor.     

Dynamic infrared scene projection: a review

Since the early 1990s, there has been major progress in the developing field of dynamic infrared scene projection, driven principally by the need for hardware-in-the-loop simulation of the oncoming generation of imaging infrared missile seekers and more recently by the needs for realistic simulation of the new generation of thermal imagers and forward-looking infrared systems. In this paper the current status of the dynamic infrared projection field is reviewed, commencing with an outline of its history. The requirements for dynamic infrared scene projection are examined, allowing a set of validity criteria to be developed. Each class of infrared projector that has been investigated—emissive, transmissive, reflective, laser scanner and phosphor—together with the specific technology initiatives within the class is described and examined against the validity criteria. In this way the leading dynamic infrared scene projection technologies are identified.     

Diamond anvil Raman gauge in multimegabar pressure range

The first-order Raman band of diamond anvils has been investigated at pressure up to 380 GPa in order to develop an optical pressure determination method. The high frequency edge of the band was calibrated by the pressure scale of the equation of state of Pt. The universality of the relationship between the sample pressure and the edge-frequency was confirmed up to 370 GPa and the usefulness of the diamond anvil Raman gauge was demonstrated. Using the diamond anvil Raman spectroscopy, the stress-state of the anvil culet was directly observed in the multimegabar pressure range. Obtained pressure dependence of the shear stress suggested further extension of feasible pressure beyond 400 GPa.     

Compact sensor for methane detection in the mid infrared region based on Quartz Enhanced Photoacoustic Spectroscopy

A compact system for methane sensing based on the Quartz-Enhanced Photoacoustic Spectroscopy technique has been developed. This development has been taken through two versions which were based respectively on a Fabry Perot quantum wells diode laser emitting at 2.3 μm, and on a quantum wells distributed feedback diode laser emitting at 3.26 μm. These lasers emit near room temperature in the continuous wave regime. A spectrophone consisting of a quartz tuning fork and one steel microresonator was used. Second derivative wavelength modulation detection was used to perform low methane concentration measurements. The sensitivity and the linearity of the QEPAS sensor were studied. A normalized noise equivalent absorption coefficient of 7.26 × 10⁻⁶ cm⁻¹ W/Hz^1/2 was achieved. This corresponds to a detection limit of 15 ppmv for 12 s acquisition time.     

Ruby-spheres as pressure gauge for optically transparent high pressure cells

Abstract

Ruby is widely used as an in siru pressure gauge for optically transparent pressure cells up to the megabar range. Usually ruby chips cut from bulk crystals are used which are ill-characterized and inconvenient to handle and to identify visually. Here we present a systematic study on corundum samples doped with Cr³⁺ ions with concentration from 60 to 23500 ppm to determine the optimal conditions for the use as an accurate pressure marker. The influence of the excitation wavelength on the luminescence spectra was investigated. These studies led to the synthesis of small (1–50 micrometer) ruby spheres with 3000 ppm chromium concentration. After annealing and a heat treatment to avoid internal strains we find reproducible values of the position and the width of the fluorescence lines. These ruby spheres are not only well suited for a reliable and accurate pressure determination in experiments using diamond anvil cells, but can also be used as an in sihr micro-thermometer in high pressure-low temperature studies.     

Biomimetic-inspired highly sensitive flexible capacitive pressure sensor with high-aspect-ratio microstructures

The high sensitivity flexible capacitive pressure sensor (FCPS) manufactured in a fast and efficient way has friendly man-machine interaction function. In this paper, a high-sensitivity FCPS is developed by using a two-step template method to reproduce biomimetic microtower polydimethylsiloxane (PDMS) from the lotus leaf surface. The capacitive sensor is composed of a PDMS dielectric layer and the Cu nanowire electrodes sandwiching in the middle, with a high sensitivity of ~1.207 kPa⁻¹, a low detection limit of less than 0.02 kPa and a fast response time of 61.6 ms. Particularly, the sensing performance can be kept basically unchanged when bent at a 5 mm radius. Moreover, the FCPS can withstand 4000 repeated tests and maintain stable performance, and the sensitivity is almost the same in the process of loading and unloading, suggesting the high robustness. These results demonstrates the FCPSs have potential applications in electronic wearables, human health monitoring and uneven surface applications.     

Dual mode ultrasonic interferometry in multi-anvil high pressure apparatus using single-crystal olivine as the pressure standard

Acoustic measurements of compressional (P) and shear (S) wave travel times were performed in a 1000-ton uniaxial split-cylinder apparatus (USCA-1000) of the Kawai-type up to 10?GPa at room temperature, using dual mode lithium niobate transducers and ultrasonic interferometry. The cell pressures were calibrated continuously by in-situ measurements of the travel times in a single crystal San-Carlos olivine buffer rod inside the cell assembly. Elastic compressional and shear wave velocities in a dense, fine-grained polycrystalline Al₂O₃ were measured simultaneously to 10?GPa; from these data, the elastic moduli and their pressure derivatives were obtained for the longitudinal modulus {L ₀?=?461(3)?GPa, L ₀′?=?7.0(1)}, the shear modulus {G ₀?=?162(2)?GPa, G ₀′?=?1.9(1)} and the bulk modulus {K ₀?=?245(3)?GPa, K ₀′?=?4.5(1)}.     

Polarization maintaining index-guided photonic crystal fiber sensor for slowly varying pressure measurement

The paper presents an experimental investigation of slowly varying pressure measurement using the polarization maintaining photonic crystal fiber (PCF) sensor. Versatility of the sensor has been proved by analyzing its response for various types of time varying pressure profiles viz. exponentially decaying, sinusoidally varying and linearly increasing pressure. Temporal behavior of the sensor has been fully characterised. Dependence on temperature has been explored and it is found that the sensor is an attractive choice for applications in harsh environments.     

用压力传感器和温度传感器测量绝对零度

介绍用贮气球体与压力传感器和温度传感器配合,在定容条件下测量气体的压强与温度,采用外推法估算理想气体可以达到的最低温度,即绝对零度的摄氏温度值,替代原先用玻璃管测体积和水银温度计测温度.使用这种绝对零度实验装置,可以更明显地观察分析热力学现象,并使测得的绝对零度值较为精确.     

Self-broadening and shifting of HI lines in the 1-0 and 2-0 infrared bands

Pressure-broadening and -shifting coefficients of pure HI at room temperature have been determined from fits of high-resolution Fourier transform spectra in the fundamental and first overtone infrared bands. The results indicate that the measured widths are almost identical in both bands and decrease significantly with the rotational quantum number. On the contrary, the pressure-induced shifts show a strong dependence on both the rotational and vibrational states. These results are compared with predictions of a semi-classical model. The latter leads to calculated values in good agreement with measurements and shows that the broadening is dominated by electrostatic interactions due to the (permanent) electric dipole and quadrupole moments. On the contrary, the observed shifts cannot be explained without the introduction of a significant vibrationally dependent isotropic potential. The effects of line coupling between hyperfine components are also discussed although they are expected to be small and cannot be observed from the measured spectra. Finally, some tabulated values of calculated widths and shifts vs. quantum numbers and temperature are proposed. They should be useful for infrared sounding of HI amounts, particularly in the monitoring of the hydrogen production through the sulfur-iodine thermochemical cycle.     

Pressure broadening and shifting parameters for the spectral lines in the fundamental vibration-rotation bands of HBr and HI in mixtures with rare gases

We report measurements of the line broadening and shifting coefficients in the (1 ← 0) fundamental absorption bands of the HBr and HI molecules in mixtures with rare gases He, Ne, Ar, Kr, and Xe. Comparison is given with the published data on other HHal-Rg systems. The measured line shifts are separated into terms symmetric and asymmetric in the line number m. The magnitudes of the symmetric shifts change in a regular manner in the series of rare gases and reach perturber-specific asymptotic values at higher ∣m∣. It is found that the asymptotic values of the symmetric line shifts linearly correlate with the respective C₆ potential energy constants and that the slopes of these correlations are proportional to the vibrational ground state dipole moments squared of the hydrogen halide molecules.     

Pressure broadening and shifting parameters for the spectral lines in the first overtone vibration-rotation bands of HBr and HI in mixtures with rare gases

We present experimental data on the previously unknown line broadening and shifting coefficients in the (2 ← 0) overtone vibration-rotation bands of the HBr and HI molecules in mixtures with several rare gases. The vibrational dependence of the isotropic and anisotropic components of the binary interaction potential is probed by separating the measured line shifts into parts symmetric and asymmetric in the line number m and by comparing with the previously published similar data for the fundamental bands of the same molecules. It is shown that the line shifts are dominated by the vibrational dependence of the isotropic potential. A linear correlation is found between the asymptotic values of the symmetric shifts in the overtone bands for all HX-Rg (X = F, Cl, Br, I) pairs and the respective C₆ long-range potential energy constants. Line broadening parameters in the overtone band of pure HBr are also reported.     

Design of midwave infrared athermalization optical system with a large focal plane array

Based on the most advanced staring focal plane array which had a format of 640 × 480 and the pixel pitch of 15 μm, a set of all-sphere midwave infrared ahermalization optical system was designed. The working wavelength was in 3–5 μm, the full field of view was 8.58°, the relative aperture was 1/2, the efficient focal length (EFL) was 80 m. The opticalsystem consisted of four lenses with three kinds of material – Ge, ZnSe and Si. All surfaces were sphere, which was easier to process test, making the cost inexpensive, and it could avoid using diffractive surface and aspheric surface. The image quality of the system approaches the diffraction limit in the temperature range −60 °C-180 °C. The design results proved that, the high resolution midwave infrared optical system had compact structure, small volume, high resolution and excellent image quality, meeting the design requirements, so that it could be used for photoelectric detection and tracking system.     

Noise reduction efforts for the ALS infrared beamlines

The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on signal-to-noise. We have successfully identified and suppressed several noise sources affecting beamlines 1.4.2, 1.4.3, and 1.4.4 at the advanced light source (ALS), resulting in a significant increase in the quality of FTIR spectra obtained. In this paper, we present our methods of noise source analysis, the negative effect of noise on the infrared beam quality, and the techniques used to reduce the noise. These include reducing the phase noise in the storage ring radio-frequency (RF) system, installing an active mirror feedback system, analyzing and changing physical mounts to better isolate portions of the beamline optics from low-frequency environmental noise, and modifying the input signals to the main ALS RF system. We also discuss the relationship between electron beam energy oscillations at a point of dispersion and infrared beamline noise.     

压力作用下石英砂岩的热红外光谱变化与敏感响应波段

在实验室对石英砂岩进行单轴压缩加载,利用红外光谱辐射计(观测波段8～14μm)对加载过程中试样的红外光谱辐射变化特征进行观测,研究岩石红外辐射对应力响应的敏感波段。实验结果显示,当岩石被加载时,红外光谱随之发生变化,但不同波段变化特征不同,在8.0～11.5μm范围(尤其在8.6～9.1μm)石英砂岩的红外光谱辐射强度随载荷增加而增加,二者间近似呈两次曲线关系,且光谱辐射强度的"信噪比"较高;在其它波段光谱辐射强度与载荷的相关性差且"信噪比"较低。由此表明,8.0～11.5μm是石英砂岩红外辐射对应力响应的敏感波段,也是岩石应力与灾变红外遥感监测的优势波段,而最佳监测波段是8.6～9.1μm。     

光纤压力传感器的性能研究

利用自制的全光纤马赫-曾德尔干涉仪,对压力引起的光功率的变化进行了测量和分析,给出了该系统相干检测最佳工作范围是5~13N,灵敏度为-0.130 0μW/N.在不同温度变化范围内,随着压力的增加,光功率分别以0.223 4μW/N到0.482 3μW/N的变化率减小.