基于固态自旋系综NV色心微波调制的磁传感技术研究（英文）

针对传统磁场检测设备分辨率低、测量精度低的现状,提出了一种基于金刚石NV色心微波频率调制进行磁检测的方法。通过频率调制方法,可以降低测量系统中低频噪音干扰,提高测量灵敏度。首先通过扫描微波频率得到ESR谱线,然后利用混合高频正弦调制信号进行频率调制,并使用锁相放大器对频率进行锁定,得到频率与光谱一阶导数成比例的信号。实验结果表明,磁场检测灵敏度可达17.628nT/Hz~(1/2)。该方法实现了高分辨率、高灵敏度的磁场检测。     

Sensitivity enhancement in ESR/ENDOR spectrometers by use of microwave amplifiers

The introduction of a low-noise microwave preamplifier in a homodyne ESR spectrometer can increase the signal-to-noise ratio by more than a factor of 10 at low modulation frequencies, and makes it superior to a superheterodyne spectrometer. The performance of this new arrangement has been compared to that of a normal homodyne spectrometer.     

新型微波等离子体炬全谱仪的研制

原子发射光谱技术广泛适用临床医学、石油化工、食品、环境等许多领域,本文基于对元素成份分析新技术的需要,研制了一台新型的微波等离子体炬原子发射光谱全谱仪。简介全谱仪的结构和工作原理、基于Modbus协议的控制系统和固态微波源、仪器的分析性能(元素的检出限和多元素同时检测能力)。结果表明,仪器运行稳定可靠,对大多数元素的检出限达到10-8～10-10g/mL水平,可以同时实现多元素同时检测。     

平面光栅摄谱仪改造为光电直读光谱仪

照相式的光栅摄谱仪常用电弧光源、相板照相、洗相及测黑度等进行发射光谱分析。我们用ICP光源、光电转换、精密机械传动、电子技术及计算机控制和数据处理等新技术,将摄谱仪改造升级为高性能ICP扫描直读光谱仪。此仪器适用于光谱定量分析、光谱分析研究和光谱教学。     

基于曲面反射镜的光谱仪用光纤集光器设计

为了提高传统光纤光谱仪的探测距离, 首次提出采用两片旋转抛物面反射镜进行光谱仪用光纤集光器入射光学设计, 将光谱仪探测距离从厘米量级提高到50 m, 可用于户外被动光源条件下超低空遥感探测. 从光纤光谱仪对集光器的性能要求出发, 推导出适用于不同灵敏度光纤光谱仪, 针对不同探测目标、 探测距离和不同天气条件下的抛物型集光器外围尺寸计算公式. 根据计算结果, 利用ZEMAX光学仿真软件设计出直径16 mm, 高7.8 mm的光纤集光器模型, 并利用TracePro光纤模拟软件进行追光分析, 光学辐射放大率的仿真结果与理论计算结果完全吻合, 误差小于0.78%. 该集光器的设计可有效提高光纤光谱仪探测距离, 拓展其应用领域和范围, 且与传统透射型集光器相比, 具有结构紧凑、 轻便化、 价格低廉等优点.     

中阶梯光栅分光光路的设计

为了实现更宽波段范围内的全谱直读并获得较高的分辨率,对中阶梯光栅光谱仪的分光系统进行了研究。简述了中阶梯光栅与中阶梯光栅光谱仪的基本原理,分析了中阶梯光谱仪和普通光谱仪的区别,详细论述了一种利用中阶梯光栅作为主要分光元件,棱镜作为交叉色散原件的中阶梯光栅分光光路的设计方法,并最终在探测面上得到了可探测分析的二维谱图。通过对设计过程的详细论述,可以为今后从事中阶梯光栅光谱仪光学设计的研究者提供参考。     

Computer Recording in Rapid Scan ESR Spectroscopy

SUMMARY

Rapid scanning [1, 2] in ESR spectroscopy is one of the methods by which one can obtain significant information relating to rapid chemical reactions occurring in several milliseconds. One of the advantages of this rapid scanning method is the ability to investigate phenomena occurring rapidly and singly, such as a decay of electrons trapped in a solid matrix. This note reports on the coupling of an electronic computer (JEOL JEC-5) with the rapid scan unit in order to record ESR spectra with high signal-to-noise ratio in several milli-seconds, and also on the successful application of this technique to the study of chemical reactions. This use of the computer is neither as a computer of average transients (CAT) [3, 5] nor as a sampling method for the detection and display of rapidly changing spectra [6, 7]. The apparatus used in this experiment consists of an ESR spectrometer, a Helmholtz coil, a power amplifier, a sawtooth wave generator, a trigger pulse generator, and an electronic computer. A block diagram of the equipment is shown in Fig. 1. Although details of the rapid scan method and the units other than the computer were described in a previous paper [2], several parts have been improved as follows. The dimensions of the Helmholtz coil were changed to 10.2 cm outer diameter and 6.5 cm inner diameter, and the unit was made of 10 turns of 0.7-mm copper wire. By feeding the sawtooth current to the coil after amplification by a solid-state SEPP OTL power amplifier a more linear field sweep was obtained than previously.? The trigger pulse, the repetition rate of which ranges from 200 msec to 10 sec, initiates simultaneously both the sawtooth wave generator and the computer. The purpose of using the computer is to store the ESR spectra observed by the rapid scan method during a rapid chemical reaction and to display these spectra on the chart of a conventional recorder after complete termination of the reaction. About 100 μsec are required for analog-to-digital conversion in the computer used. Sixteen ESR spectra, each of which was ob served for 20 msec, were stored in the computer during a chemical reaction. For this operation a program was compiled so as to store 192 sampling points for each spectrum; the number of these sampling points was sufficient to get a precise and smooth curve for each spectrum displayed. The application of the technique was demonstrated for an experiment on the decay reaction of the electrons trapped in 2-methyltetrahydrofuran, MTHF.     

A high-selectivity β spectrometer

Measurements of β spectra from fission fragments are complicated by high background of γ rays and neutrons. A scintillation β spectrometer capable of precisely reconstructing the β particle spectra in the energy range of >1 MeV has been developed to reduce the effect of this background without deteriorating the high detection efficiency for β particles. The functional diagram of the spectrometer is described, and the results of spectrometer testing using radioactive electron sources are presented.     

Versatile Microprocessor Based Interface for Electron Spin Resonance (ESR) Spectrometer

ABSTRACT

A Motorola M6800 based interface to an ESR spectrometer is described. The interface extends the capability of a conventional ESR spectrometer to enable it to perform a variety of additional tasks, e.g. signal averaging, transient recording, etc. at a minimal cost.     

Characteristics of the system of polarization-optical detection of a pulsed terahertz spectrometer

Characteristics of a system of polarization-optical detection of a pulsed terahertz spectrometer in nonlinear crystals of zinc telluride (ZnTe) are considered. The influence of the ZnTe crystal thickness (0.5, 1, and 2 mm) on the detection system sensitivity is studied experimentally; a comparison with model calculations is performed. The effect of the time step and the interval of scanning of the terahertz pulse on the spectral resolution and range of the spectrometer is demonstrated experimentally and theoretically. Terahertz transmission spectra of typical container materials are measured.     

An attenuated total reflectance far-UV spectrometer

An ultraviolet spectrometer based on attenuated total reflection (ATR) has been developed and tested for liquid water (light and heavy water) in the wavelength range from 140 to 300 nm, which includes the far ultraviolet (FUV) region. One of the principal limitations of FUV transmission spectra is the strong absorption of the solvent itself. High absorptivity of the n --> sigma(*) transition in water molecule has thus far prevented meaningful spectral measurements of aqueous solutions in the wavelength region under 170 nm. Our technique uses the evanescent wave created through total reflection when light is passed through an internal reflection element (IRE) in contact with the sample. Since the evanescent field is used as an optical path length, the method allows spectral measurements favorably comparable with that of transmittance method with a shorter path length than the wavelength of FUV light. In this study, we have designed an original miniature IRE probe made of sapphire that allows detection of the whole n --> sigma(*) transition absorption band of water down to 140 nm. The obtained ATR-FUV spectra closely match calculations based on the Fresnel formula. It is also confirmed that this spectrometer is equally effective for spectral measurements of nonaqueous solvents with significant absorptivities in the FUV region.     

Broadband electron spin resonance at low frequency without resonant cavity

We have developed a nonconventional broadband electron spin resonance (ESR) spectrometer operating continuously in the frequency range from 0.5 to 9 GHz. Dual antenna structure and the microwave absorbing environment differentiate the setup from the conventional one and enable broadband operation with any combination of frequency or magnetic field modulation and frequency or magnetic field sweeping. Its performance has been tested with the measurements on a 1,1-diphenyl-2-picrylhydrazyl (DPPH) sample and with the measurements on the single molecular magnet, V6, in solid state at low temperature.     

Spatial and spectral calibration of an acousto-optical spectrometer

The problem of determining the optical spectra at separate points of images that are recorded with an endoscopic acousto-optical spectrometer is considered. The factors that cause distortions in images and spectra are investigated. Algorithms for calibration of this type of instruments and digital data correction for the sequential elimination of distortions of various types are developed. In a model experiment, it is shown that the proposed algorithm provides a quite high quality of determining spectra at arbitrary points of the field of vision.     

Base-line suppression in microwave spectroscopy using frequency modulation and harmonic detection

In a microwave spectrometer, systematic variations of the rf source amplitude with frequency can cause a spurious signal (base line) which severely limits the attainable sensitivity. Normally, the base line is eliminated by using Stark or Zeeman modulation. However, these modulation methods cannot be used in an experiment on nonparamagnetic molecular ions contained in a glow discharge. This paper discusses a technique which we have used to reduce the base line by a factor of about 10(-5) and which can be used to study the spectra of species contained in a glow discharge. The scheme uses wideband sinusoidal frequency modulation of the microwave source combined with synchronous detection at the nth harmonic of the modulation frequency. The system produces a signal proportional to the nth derivative with respect to frequency of the base line. However, the signal due to an absorption line is only slightly smaller than that produced by other modulation methods. The system may be considered to behave like a high-pass filter which discriminates against features that vary slowly with frequency.     

Small-size terahertz spectrometer using the second harmonic of a femtosecond fiber laser

Possible implementations of a small-size terahertz spectrometer with a subpicosecond resolution on the basis of a femtosecond fiber laser are considered. An experimental sample of a spectrometer is fabricated. This spectrometer employs the method of optical rectification in a ZnTe nonlinear crystal and the Dember (photodiffusion) effect on the InAs semiconductor surface to generate terahertz radiation and the polarization-optical method to detect radiation. System operation is demonstrated by an example of measuring the terahertz absorption spectrum of water and determining the refractive index of the β-BBO crystal. The basic spectrometer parameters are found: spectral range, spectral resolution, and dynamic range of the terahertz spectrum amplitude.     

Development of neutron spectrometer toward deuterium plasma diagnostics in LHD

Neutron spectrometer based on coincident counting of associated particles has been developed for deuterium plasma diagnostics on Large Helical Device (LHD) at the National Institute for Fusion Science. Efficient detection of 2.5 MeV neutron with high energy resolution would be achievable by coincident detection of a scattered neutron and a recoiled proton associated with an elastic scattering of incident neutron in a plastic scintillator as a radiator. The calculated neutron spectra from deuterium plasma heated by neutral beam injection indicate that the energy resolution of better than 7% is required for the spectrometer to evaluate energetic deuterium confinement. By using a prototype of the proposed spectrometer, the energy resolution of 6.3% and the detection efficiency of 3.3×10(-7)?count/neutron were experimentally demonstrated for 2.5 MeV monoenergetic neutron, respectively.     

A search accelerated correct intensity Fourier transform microwave spectrometer with pulsed laser ablation source

The ablation of metal surfaces in the presence of a precursor gas produces reaction products which are often difficult to predict and highly dependent on ablation conditions. This article describes the successful development and implementation of a laser ablation source-equipped Fourier transform microwave spectrometer capable of observing 4 GHz regions of spectra in a single data acquisition event. The dramatically increased speed with which regions may be searched, when compared to other high resolution microwave techniques, allows the source conditions to be the prime variable in laser ablation microwave spectroscopic studies. A second feature of the technique is that observed spectral features have correct relative intensities. This is advantageous when assigning observed spectra. The study of two metal chlorides, AgCl and AuCl, illustrate the instrument's benefits.     

紫外-可见光双通道拉曼光谱仪光学设计

紫外拉曼光谱技术具有高强度拉曼散射、无荧光干扰的特点;可见光拉曼光谱技术可实现低波数、高分辨率探测。为兼具两种激发波长的优势,设计了一款对称分布的双Czerny-Turner光路聚焦于一个探测器的双通道拉曼光谱仪。通过元器件的选型和初始结构的计算,在不增加多余元器件的情况下,对弧矢方向像散进行补偿,避免了像面上的能量损失。配合Zemax软件对双通道光谱分别进行建模优化,最终实现了对400~5000 cm^-1（266 nm激发）和50~3500 cm^-1（633 nm激发）两段光谱的同时探测。均方根半径、点列图和调制传递函数等评价指标有效验证了设计的合理性和可行性。结果表明,两套拉曼光谱仪分别可达8 cm^-1和5 cm^-1分辨率,本设计具有高分辨率、低波数、多波长激发、集成化等优势。     

Design, construction, and testing of a large-cavity, 1-10 GHz Flygare-Balle spectrometer

A large pulsed-beam, Fourier transform microwave spectrometer employing 48 in. diameter mirrors and 35(") (NHS-35) diffusion pump has been constructed at the University of Arizona. The Fabry-Perot-type cavity, using the large mirrors provides Q-values in the 15,000 to 40,000 range. Test spectra were obtained using transverse and coaxial injection of the pulsed-nozzle molecular beams. The measured molecular resonance linewidths were 8 kHz for the transverse injection and 2 kHz for coaxial molecular beam injection. Good signal to noise ratios were obtained for the test signals. Strong lines for butadiene iron tricarbonyl were seen with a single beam pulse (S/N = 5/1). Transitions were measured as low as 900 MHz and some previously unresolved hyperfine structure is now resolved for the butadiene iron tricarbonyl spectra. The spectrometer is operated using a personal computer with LABVIEW programs, with provisions for automatic frequency scanning. The extended, low-frequency range of this spectrometer should make it very useful for making measurements on significantly larger molecules and complexes than have been previously studied. The improved resolution, in the coaxial beam mode, will allow better resolution of hyperfine structure. The large diffusion pump allows a higher beam pulse frequency to compensate for the generally lower sensitivity at lower frequencies.     

Detection of neutrons and γ rays by a xenon pulsed ionization chamber

The applicability of a xenon γ-ray spectrometer based on a high-pressure (50 atm) xenon cylindrical ionization chamber to thermal neutron detection is discussed. The reaction of radiative capture of thermal neutron capture ¹³¹Xe(n, γ)¹³²Xe* followed by emission of 668-keV γ rays detectable by the spectrometer is used. The response of the xenon spectrometer with a sensitive volume of 0.2 L is analyzed. The measured thermal neutron detection efficiency is 0.08%. The advantage of the detector is its capability of simultaneously detecting both thermal neutrons and γ rays, which allows precise and high-efficiency identification of radioactive and fissile materials.