Laser-locked, continuously tunable high resolution cavity ring-down spectrometer

A continuous-wave cavity ring-down spectrometer with sub-MHz precision has been built using the sideband of a frequency stabilized laser as the tunable light source. The sideband is produced by passing the carrier laser beam through an electro-optic modulator (EOM) and then selected by a short etalon on resonance. The carrier laser frequency is locked to a longitude mode of a thermo-stabilized Fabry-Perot interferometer (FPI) with a long-term absolute frequency stability of 0.2 MHz (5 × 10(-10)). Broad and precise spectral scanning is accomplished, respectively, by selecting a different longitudinal mode of the FPI and by tuning the radio-frequency driving the EOM. The air broadened water absorption line at 12,321 cm(-1) was studied to test the performance of the spectrometer.     

A rigid, monolithic but still scannable cavity ring-down spectroscopy cell

A novel cell for continuous wave cavity ring-down spectroscopy (cw-CRDS) is described and tested. The cell is monolithic and maintains a rigid alignment of the two cavity mirrors. Two high-resolution and high-force piezoelectric transducers are used to sweep the length of the cell by elastic deformation of the 2.86 cm outer diameter stainless steel tube that makes up the body of the cell. The cavity length is scanned more than 1/2 wavelength of the near-IR light used, which ensures that at least one TEM(00) mode of the cavity will pass through resonance with the laser. This allows the use of a frequency-locked-laser cw-CRDS technique, which increases the precision of the measurements compared to the alternative of sweeping the laser more than one free spectral range of the cavity. The performance of the cell is demonstrated by using it to detect the absorption spectrum of methane (CH(4)) at the wavenumber regions of around 6051.8-6057.7 cm(-1).     

用光腔衰荡法测量高反射率的重复性测试

根据光腔衰荡光谱技术开展了测量镜片高反射率的研究,建立了测量实验装置,理论上给出了反射率测量的计算方法,在实验中测定了一对反射率相等的高反射腔镜的反射率,以及一块22.5°反射镜样品的反射率,所得反射率的标准偏差好于10-5。该仪器具有较高的实验重复性。     

用光腔衰荡法测量高反射率的实验研究

根据光腔衰荡光谱技术开展了测量镜片高反射率的研究,建立了测量实验装置。理论上给出了反射率测量的计算方法,在实验中测定了一对反射率相等的高反射腔镜的反射率,以及一块45°反射镜样品的反射率,并分析了影响光腔衰荡曲线的参数。     

一次谐波锁频的快速光腔衰荡光谱检测

本文介绍了一种赫兹级响应速率的光腔衰荡光谱探测大气痕量气体的检测技术.将100 MHz正弦波调制信号加载在电光相位调制器上产生边带,用混频器提取载波与边带通过3m气体吸收池后拍频所产生的一次谐波作为误差信号,实现了1572 nm分布式反馈激光器对于二氧化碳气体分子6361.25 cm-1处超精细跃迁线的频率锁定.采用波...     

Design of a cavity ring-down spectroscopy diagnostic for negative ion rf source SPIDER

The rf source test facility SPIDER will test and optimize the source of the 1 MV neutral beam injection systems for ITER. Cavity ring-down spectroscopy (CRDS) will measure the absolute line-of-sight integrated density of negative (H(-) and D(-)) ions, produced in the extraction region of the source. CRDS takes advantage of the photodetachment process: negative ions are converted to neutral hydrogen atoms by electron stripping through absorption of a photon from a laser. The design of this diagnostic is presented with the corresponding simulation of the expected performance. A prototype operated without plasma has provided CRDS reference signals, design validation, and results concerning the signal-to-noise ratio.     

Evaluation of carrier gases for high-precision water isotopic measurements by cavity ring-down laser spectroscopy

The carrier gas is important for obtaining stable, precise hydrogen and oxygen isotopic ratios in water samples using cavity ring-down laser spectroscopy. The δ²H and δ¹⁸O variations were investigated using four carrier gases under two microcombustion conditions. Although most deviations of δ²H and δ¹⁸O values were within the standard deviation of the instrument, statistical analysis indicated that carrier gas provided by a drying tube with higher water background was not suitable for cavity ring-down laser spectroscopy. In addition, the microcombustion on condition did not significantly improve the precision and accuracy of δ²H and δ¹⁸O measurements. Therefore, the best method for achieving highly precise results involved the use of low water containing compressed air as the carrier gas with the microcombustion warm condition.     

Determination of refractive index by fiber-loop cavity ring-down spectroscopy and a long-period fiber grating

The combination of fiber-loop ring-down spectroscopy and a long-period fiber grating were employed in an intensity-interrogated refractive index sensing method using a broad band light source and the specifically designed long-period fiber grating. Compared with the traditional long-period-fiber-grating based refractive index sensors, this approach monitored the decay of the optical signal passing through the loop of the long fiber grating. The decay time changed regularly when the grating was immersed in surrounding media with varying refractive indices. This instrumentation offered reduced cost and eliminated the influence of source fluctuation. The sensitivity and resolution were 2421 ns/RIU and 3 × 10^?4 for refractive index values from 1.3330–1.3737.     

Note: Vector network analyzer-ferromagnetic resonance spectrometer using high Q-factor cavity

A ferromagnetic resonance (FMR) spectrometer whose main components consist of an X-band resonator and a vector network analyzer (VNA) was developed. This spectrometer takes advantage of a high Q-factor (9600) cavity and state-of-the-art VNA. Accordingly, field modulation lock-in technique for signal to noise ratio (SNR) enhancement is no longer necessary, and FMR absorption can therefore be extracted directly. Its derivative for the ascertainment of full width at half maximum height of FMR peak can be found by taking the differentiation of original data. This system was characterized with different thicknesses of permalloy (Py) films and its multilayer, and found that the SNR of 5 nm Py on glass was better than 50, and did not have significant reduction even at low microwave excitation power (-20 dBm), and at low Q-factor (3000). The FMR other than X-band can also be examined in the same manner by using a suitable band cavity within the frequency range of VNA.     

Double axis, two-crystal x-ray spectrometer

A two-crystal double axis x-ray spectrometer, capable of goniometric accuracy on the order of 0.1", has been developed. Some of its unique design features are presented. These include (1) a modified commercial thrust bearing which furnishes a precise, full circle theta:2theta coupling, (2) a new tangent drive system design in which a considerable reduction of the lead screw effective pitch is achieved, and (3) an automatic step scanning control which eliminates most of the mechanical deficiencies of the tangent drive by directly reading the tangent arm displacement.     

浅析波长扫描光腔衰荡光谱技术

波长扫描腔衰荡光谱技术是一种新型的光谱检测方法,由于该技术具有吸收光程长,不受光源强度起伏影响的特点,因而受到国内外的广泛重视,已被应用于监测分子及原子体系。波长扫描光腔衰荡光谱技术在痕量元素监测分析中的应用,证明它完全可以在通用的原子吸收分光光度计上实现。它的主要用途是进行多元素分析。能够带来一些其它的扩展功能,是一种很有发展前途的新技术。     

Refractive index sensor based on fiber loop ring-down spectroscopy

An optical fiber refractive index sensor based on fiber loop ring-down spectroscopy and a tapered fiber was fabricated using an ordinary single mode fiber with an arc fusion splicer. The performance of the sensor was controlled by the parameters of the tapered fiber. A fiber loop ring-down spectroscopy system was employed to enhance the sensitivity and demodulate the transmission spectrum. The results showed that a sensor with a waist diameter of 14 m and a length of 1.2 mm had good optical performance. By monitoring the ring-down time of the system, relatively high sensitivity of 411.576 s/ RIU was achieved with refractive index values from 1.333 to 1.412. This sensor offers few interferences, high sensitivity, easy fabrication, and low cost.     

High-resolution,energy-dispersive microcalorimeter spectrometer for X-ray microanalysis

We have developed a prototype X-ray microcalorimeter spectrometer with high energy resolution for use in X-ray microanalysis. The microcalorimeter spectrometer system consists of a superconducting transition-edge sensor X-ray microcalorimeter cooled to an operating temperature near 100 mK by a compact adiabatic demagnetization refrigerator, a superconducting quantum interference device current amplifier followed by pulse-shaping amplifiers and pileup rejection circuitry, and a multichannel analyser with computer interface for the real-time acquisition of X-ray spectra. With the spectrometer mounted on a scanning electron microscope, we have achieved an instrument response energy resolution of better than 10 eV full width at half-maximum (FWHM) over a broad energy range at real-time output count rates up to 150 s^?1. Careful analysis of digitized X-ray pulses yields an instrument-response energy resolution of 7.2 ± 0.4 eV FWHM at 5.89 keV for Mn Kα_1,2 X-rays from a radioactive ⁵⁵Fe source, the best reported energy resolution for any energy-dispersive detector.     

A compact frequency-stabilized pulse-periodic waveguide CO2 laser for calibration of wavelength meters

A compact pulse-periodic waveguide CO₂ laser with high-frequency excitation with automatic assignment of the 10P (14) line and stabilization of the emission frequency in the middle of this line using a sealed-off optoacoustic cell, which is filled with a mixture of C₂H₄ (0.1%) and nitrogen, was developed. It is shown that the laser-frequency instability is within 3 MHz, thus meeting the requirements that are imposed on the calibration tools for high-resolution wavelength meters that are similar to WS-6IR.     

A meridional spectrometer

An imaging meridional spectrometer intended for studying the spectral composition and spatial distribution of night airglow and aurora is described. The spectrometer allows obtainment of 2D images of the major arc of the celestial hemisphere from 0° to 180° in the wavelength range 420–875 nm. The instrument has been developed in a field version, is operable under any meteorological conditions, and can operate both independently and as a component of a network data-acquisition system. Instrumental distortions of the obtained 2D images are analyzed and methods developed for their elimination are presented. The parameters of an ST-10XME CCD camera incorporated in the S180 spectrometer have been studied, and a mathematical model describing its characteristics has been developed. The software package developed for the spectrometer enables processing of the yielded data in a semiautomatic mode with allowance for errors induced by instrumental distortions. Primary processing of the results of spectrometric measurements of auroras at the Spitsbergen archipelago has been performed.     

三重四级杆质谱仪的安装应用和维护

质谱技术已经成为一种重要的现代分析鉴定技术,三重四级杆质谱,采用空间串联四级杆分析器,对选择离子分析具有较高灵敏度,应用广泛.建议专人负责质谱的安装,管理,应用及维护.维持稳定的电源,充足的液氮和氮气,及时清洗和维护,以保证质谱仪正常,稳定的工作.     

Interfacing an aspiration ion mobility spectrometer to a triple quadrupole mass spectrometer

This article presents the combination of an aspiration-type ion mobility spectrometer with a mass spectrometer. The interface between the aspiration ion mobility spectrometer and the mass spectrometer was designed to allow for quick mounting of the aspiration ion mobility spectrometer onto a Sciex API-300 triple quadrupole mass spectrometer. The developed instrumentation is used for gathering fundamental information on aspiration ion mobility spectrometry. Performance of the instrument is demonstrated using 2,6-di-tert-butyl pyridine and dimethyl methylphosphonate.     

低成本光谱仪的研制

为了满足高校教学和人才培养的需求,便于系统的小型化、低成本,设计了低成本光谱仪的光学系统和机械结构,制作了低成本的光谱仪实物并完成了对仪器的性能测试。该光谱仪的工作波长为400~800nm,分辨率为20nm,仪器尺寸为200mm×120mm×80mm,成本控制在2 000元以内。通过对仪器的测试,获得了六个光谱特征峰,验证了低成本光谱仪系统光学设计的可行性和合理性。