Hot-electron bolometer terahertz mixers for the Herschel Space Observatory

We report on low noise terahertz mixers (1.4-1.9 THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performance was characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5 to 2.5 THz, with 30 GHz resolution) and also by measuring the mixer noise temperature at a limited number of discrete frequencies. The lowest mixer noise temperature recorded was 750 K [double sideband (DSB)] at 1.6 THz and 950 K DSB at 1.9 THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4-4.8 GHz, the mixer noise temperature was 1100 K DSB at 1.6 THz and 1450 K DSB at 1.9 THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEB stability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200-500 nW range.     

A terahertz spectrometer with a pulsed high magnetic field

A terahertz (THz) spectrometer based on backward-wave tubes and combined with a pulsed-magnetic-field generator with a pulse duration of ～100 μs and an amplitude of up to 50 T is described. This spectrometer is indented for studying magnetic resonances of various magnets in the THz frequency range (30 GHz-1.5 THz) in the Faraday (longitudinal field) and Voigt (transverse field) geometries. Its operating principle is based on measurements of the change in the transmission of polarized THz radiation by studied samples exposed to an applied pulsed magnetic field. Its advantage over the magnetic-resonance technique, in which radiation guides with uncontrolled radiation polarization are used, is the possibility of performing precise polarization measurements necessary for determining the conditions for excitation of resonance magnetic modes and yielding important information on the magnetic structure of materials. The results of polarization measurements of test samples are presented. The degree of radiation polarization is 99.99%; the dynamic measurement range is 25 dB; the measurement accuracy is no worse than 1%; the time resolution of the recording system is 1s; the magnetic-field inhomogeneities at the solenoid’s center at a base of ±2 mm are no worse than 1 (experimental) and 5% (calculated) for the axial and radial components, respectively; and the maximum stored energy is 40.5 kJ.     

Image sensor as a three-channel spectrometer with application to in situ monitoring of wet etching

A three-channel spectrometer is constructed with a 460 nm high brightness light-emitting diode (LED) source (250 mW peak optical power output, 1 mm sq, 150 μm thick) and a red-green-blue (RGB) image sensor (3 × 4 mm, 1 mm thick) for purposes of a small form factor spectrometer to monitor reflectance/emission spectra from chemical wet etching experiments. The linearity and spectral response of the RGB image sensor is characterized and a three-channel spectral model is fitted to the extracted spectral response. We use this information to quantify time developments of the RGB image sensor outputs for in situ copper and aluminum etching experiments in terms of three defined spectral bands.     

基于太赫兹光谱的天冬氨酸结构分析及鉴定

太赫兹时域光谱技术（THz-TDS）是一种新的远红外波段光谱测量技术,对化合物结构上的微小差异变化十分敏感,因此成为物质分析与检测的新型方法。文章基于太赫兹时域光谱技术的测定方法,在氮气环境中考察不同来源天冬氨酸在太赫兹波段的吸收特性,并结合差示扫描量热仪（DSC）和傅立叶变换红外光谱仪（FITR）进一步验证THz测定结果的有效性。实验结果表明,用太赫兹时域光谱技术可以清楚地分辨出不同结构天冬氨酸的差异,方法简单,快速,准确。     

New-generation of cryogenic sapphire microwave oscillators for space, metrology, and scientific applications

This article reports on the characterization of cryogenic sapphire oscillators (CSOs), and on the first test of a CSO in a real field installation, where ultimate frequency stability and continuous operation are critical issues, with no survey. Thanks to low-vibration liquid-He cryocooler design, Internet monitoring, and a significant effort of engineering, these oscillators could bridge the gap from an experiment to a fully reliable machine. The cryocooler needs scheduled maintenance every 2 years, which is usual for these devices. The direct comparison of two CSOs demonstrates a frequency stability of 5 × 10(-16) for 30 s ≤ τ ≤ 300 s integration time, and 4.5 × 10(-15) at 1 day (1 × 10(-14) typical). Two prototypes are fully operational, codenamed ELISA and ULISS. ELISA has been permanently installed the new deep space antenna station of the European Space Agency in Malargu?e, Argentina, in May 2012. ULISS is a transportable version of ELISA, modified to fit in a small van (8.5 m(2) footprint). Installation requires a few hours manpower and 1 day of operation to attain full stability. ULISS, intended for off-site experiments and as a technology demonstrator, and has successfully completed two long-distance travels.     

小型高性能质子转移反应飞行时间质谱仪的研制及其在呼吸气成分分析中的应用

研制可快速、在线分析挥发性有机物(volatile organic compounds,VOCs)的质谱仪器是现代气态有机质谱的重要发展方向.本研究自行研制了小型高性能质子转移反应飞行时间质谱仪(proton transfer reaction time of flight mass spectrometry,PTR-...     

混沌流微混合器的性能优化

为提高低雷诺数层流条件下被动式微混合器的效率,依据"三维马蹄变换"数学模型,对流体进行"挤压拉伸""弯曲折叠""二次折叠"和"逆变换-交集"操作,得到了一款包含6个混合单元,总长度为15 mm的混沌流微混合器.仿真研究表明:在"低流速-扩散主导"阶段u=2×10-4 m/s时,t=300 s后混合器进入稳定混合状态,出...     

A broadband Fourier transform microwave spectrometer based on chirped pulse excitation

Designs for a broadband chirped pulse Fourier transform microwave (CP-FTMW) spectrometer are presented. The spectrometer is capable of measuring the 7-18 GHz region of a rotational spectrum in a single data acquisition. One design uses a 4.2 Gsampless arbitrary waveform generator (AWG) to produce a 1 mus duration chirped pulse with a linear frequency sweep of 1.375 GHz. This pulse is sent through a microwave circuit to multiply the bandwidth of the pulse by a factor of 8 and upconvert it to the 7.5-18.5 GHz range. The chirped pulse is amplified by a traveling wave tube amplifier and broadcast inside the spectrometer by using a double ridge standard gain horn antenna. The broadband molecular free induction decay (FID) is received by a second horn antenna, downconverted, and digitized by a 40 Gsampless (12 GHz hardware bandwidth) digital oscilloscope. The second design uses a simplified pulse generation and FID detection scheme, employing current state-of-the-art high-speed digital electronics. In this spectrometer, a chirped pulse with 12 GHz of bandwidth is directly generated by using a 20 Gsampless AWG and upconverted in a single step with an ultrabroadband mixer. The amplified molecular emission is directly detected by using a 50 Gsampless digital oscilloscope with 18 GHz bandwidth. In both designs, fast Fourier transform of the FID produces the frequency domain rotational spectrum in the 7-18 GHz range. The performance of the CP-FTMW spectrometer is compared to a Balle-Flygare-type cavity-FTMW spectrometer. The CP-FTMW spectrometer produces an equal sensitivity spectrum with a factor of 40 reduction in measurement time and a reduction in sample consumption by a factor of 20. The CP-FTMW spectrometer also displays good intensity accuracy for both sample number density and rotational transition moment. Strategies to reduce the CP-FTMW measurement time by another factor of 90 while simultaneously reducing the sample consumption by a factor of 30 are demonstrated.     

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。     

RGA10质谱计的改进及在K-Ar、Ar-Ar同位素定年中的应用

对 RGA1 0质谱计离子源、分析室、样品提纯系统及数据处理系统等方面进行了改进 ,并增加了 3 8Ar大小球分取装置 ,使该仪器灵敏度、真空度及仪器的综合指标比过去有了较大改善 ,仪器的稳定性及测试样品的速度有了很大提高。仪器改造后三年来的实验证明 :Ar同位素的分析效率提高了 2至 3倍。     

热障涂层折射率与厚度的太赫兹无损检测

精确提取陶瓷层（Top coat,TC）与热生长氧化层（Thermally grown oxide,TGO）层在太赫兹频段的折射率是进行热障涂层（Thermal barrier coatings,TBCs）太赫兹无损检测研究的重要条件。由于对涂层样品只能采取反射式测量,所以首先比较了反射式与传统透射式测量条件下提取样品太赫兹光学参数及厚度的结果,随后利用反射式太赫兹时域脉冲成像系统提取等离子体喷涂的8YSZ热障涂层（TBCs）中TC层与TGO层的折射率,并依据所提取折射率进一步对TC层的厚度分布进行测量及成像。试验结果表明在材料中衰减较小的有效频段下反射式测量同样可以精确提取样品的折射率以及厚度,反射式测量TC层的平均折射率为5.23,TGO层的折射率为2.91,TGO的主要成分α-Al₂O₃的折射率为2.85。TBCs样品中TC层的平均厚度为257 μm,从TC层厚度的太赫兹图像中可观察到TC与粘结层（Bond coat,BC）界面的不均匀程度。反射式太赫兹无损检测可精确提取TBCs中TC与TGO的折射率和厚度,这对于TBCs中裂纹和气泡等缺陷的识别以及TGO生长太赫兹检测具有重要意义。     

激光共振电离质谱及其在核技术中的应用

激光共振电离质谱是激光共振电离技术和质谱技术相结合的一种新型质谱分析技术,具有高元素选择性和高灵敏度的特点,能有效克服商业质谱仪存在的同量异位素干扰难题。为满足复杂基体干扰下超痕量核素分析测量的需求,实验室研制了一台基于磁 电双聚焦质量分析器的激光共振电离质谱仪。该装置的质量分析器采用正向Nier-Johnson型双聚焦结构,由柱形静电分析器和扇形磁质量分析器组成。本文介绍了仪器质量分析器的结构和理论参数,并对其进行理论仿真与实验测试。结果表明,该仪器实现了方向和能量双方向聚焦,具有较小的高阶像差,仪器的水平方向放大率为0.78,质量色散达到500 mm,当源狭缝宽度0.25 mm、探测器入口狭缝宽度0.65 mm时,质量分辨率（10%峰谷）达到580左右,接近质量分辨率的理论极限605。最后,介绍了本实验室利用该仪器开展的分析测量工作,展示了该装置在强同量异位素干扰下超痕量核素测量方面的部分应用情况。     

Sensitive Faraday rotation measurement with auto-balanced photodetection

A magneto-optic polarimetry based on auto-balanced photodetection is investigated. In this experiment, a commercial auto-balanced photoreceiver is adopted to measure the Faraday rotation of air. With a proper setup to utilize its noise cancellation capability, the measurement can be flexible and sensitive. The angular sensitivity is 2.99×10(-8) rad Hz(-1/2), which is about 2.7 times the shot noise limit. The measured Verdet constant of air is +1.39×10(-9) rad G(-1) cm(-1) at 634.8 nm. Significantly we applied a small AC current to induce the magnetic field, so there was no heating in the coil. In addition, a double current modulation scheme was used to demonstrate that there was no zero drift and amplifier instability in the measurement. The possibility of improvement of the angular sensitivity and the potential applications are also discussed.     

Application of superlattice multipliers for high-resolution terahertz spectroscopy

Frequency multipliers based on superlattice (SL) devices as nonlinear elements have been developed as radiation sources for a terahertz (THz) laboratory spectrometer. Input frequencies of 100 and 250 GHz from backward wave oscillators have been multiplied up to the 11th harmonic, producing usable frequencies up to 2.7 THz. Even at these high frequencies the output power is sufficient for laboratory spectroscopy. Comparisons to conventional high-resolution microwave spectroscopy methods reveal several superior features of this new device such as very high line frequency accuracies, broadband tunability, high output power levels at odd harmonics of the input frequency up to high orders, and a robust applicability.     

扩大粘度基准量程的研究

对扩大粘度基准量程作了研究 ,包括高粘度标准物质 (聚异丁烯 )性能及定值方法 ,特别是高粘度物质在毛细管法中残留量影响的研究。通过研究使粘度基准量程提高了一个数量级 ,从 1× 10 5mm2 /s提高到 1×10 6mm2 /s。该量程基准的测量不确定度为 0 7%～ 1% ,达到国际先进水平     

Non-contact measurement of displacer motion of a miniature split-Stirling cryocooler

A relative displacement measurement method is originally proposed to calibrate the static sensitivity of the measurement of displacer motion inside the cold finger of a split-type Stirling cryocooler. This measurement is non-contact and non-destructive by the use of the well-known linear variable-differential transformer (LVDT). Therefore the cooler operates in normal conditions without any interference, such as loading effects, from the measurement. The true displacement of the displacer is the product of the output voltage from the LVDT and the calibrated static sensitivity. Since the displacer motion consists of multiple sinusoidal signals and its oscillation center drifts continuously, modifications are made to get a better estimation of the static sensitivity. Both the direct fitting method and the small drift modification method are investigated through computer simulations, and are used successfully in experiments on a Hughes 7013H cooler.     

Grating spectrometer system for beam emission spectroscopy diagnostics using high-energy negative-ion-based neutral beam injection on LHD

A beam emission spectroscopy (BES) system was developed for density gradient and fluctuation diagnostics in the Large Helical Device (LHD). In order to cover the large Doppler shift of the Hα beam emission because of the high-energy negative-ion-based neutral beam atom (acceleration voltage V(acc)=90-170?kV) and the large motional Stark splitting due to the large v×B field (magnetic field B=3.0?T), a grating spectrometer was used instead of a conventional interference filter system. The reciprocal linear dispersion is about 2 nm/mm, which is sufficient to cover the motional Stark effect spectra using an optical fiber with a diameter of 1 mm.     

人体运动跟踪中MEMS姿态测量单元设计与测试

人体运动姿态的实时跟踪在运动员辅助训练和康复医学中有广泛应用.设计了应用于人体运动姿态测量的MEMS姿态测量单元.该姿态测量单元包含三轴正交的MEMS加速度计、磁强计和角速率陀螺,集成微控制器以及扩展数据存储的FLASH芯片,单元大小为38 mm×28 mm×13 mm.姿态角解算采用基于四元数的扩展卡尔曼滤波算法.提出了一种利用单轴转台和楔角器进行姿态测量单元3个姿态角误差测试的新方法.测试结果表明:3个姿态角测量误差均小于2°,满足人体运动姿态测量的精度要求.     

小型磁偏转质谱计研究

基于磁质谱离子光学成像聚焦原理对其离子光学系统、离子源和质量分析器的物理参数及几何结构尺寸进行优化,研制了新型小型磁偏转质谱计,其质量为4.3 kg,体积为（220×164×162） mm³,功耗为25 W。对质谱计的质量范围、灵敏度、分辨能力、最小可检漏率和稳定性等性能指标开展实验研究。结果表明,该质谱计的质量范围为1~134 u,大通道和小通道50%峰高处的分辨能力分别为56和13,对氩气、氮气和氦气的灵敏度分别为1.63×10^-4、1.17×10^-4、2.3×10^-5 A/Pa,最小可检漏率为1.24×10^-10 Pa·m³/s,仪器在3.5 h内的稳定性为2.5%。     

Design and test of miniaturized glass ceramics HeNe laser with frequency and intensity simultaneously stabilized

A miniaturized HeNe laser with intensity and frequency simultaneously stabilized is described. The laser uses a monoblock glass ceramics as its tube to construct an improved steady structure. The closed loop cavity length control system stabilizes its frequency and the discharge current regulating system stabilizes its intensity. The electronic system integrating power supply and stabilization system is designed within two small circuit boards. The laser tube and circuit boards are assembled into a small package with dimensions of 180?mm×100?mm×150?mm. The laser outputs s-polarized light at wavelength of 632.99 nm with power of 0.44 mW. Test results show that its frequency stability can reach 8.4×10(-11) (1s Allan variance over 3 h) and frequency reproducibility at 1.3×10(-8). The laser's intensity stability is 0.011% over 9 h.