A magnetic transport electron spectrometer for in-beam measurements

A compact magnetic transport electron spectrometer has been built having an overall efficiency of 0.92%, a resolution Δp/p of 18% and a maximum transmitted energy of 3 MeV. Limitations to accuracy in intensity measurements due to non-isotropic electron angular distributions have been discussed.     

In situ azimuthal rotation device for linear dichroism measurements in scanning transmission x-ray microscopy

A novel miniature rotation device used in conjunction with a scanning transmission x-ray microscope is described. It provides convenient in situ sample rotation to enable measurements of linear dichroism at high spatial resolution. The design, fabrication, and mechanical characterization are presented. This device has been used to generate quantitative maps of the spatial distribution of the orientation of proteins in several different spider and silkworm silks. Specifically, quantitative maps of the dichroic signal at the C 1s-->pi* (amide) transition in longitudinal sections of the silk fibers give information about the spatial orientation, degree of alignment, and spatial distribution of protein peptide bonds. A new approach for analyzing the dichroic signal to extract orientation distributions, in addition to magnitudes of aligned components, is presented and illustrated with results from Nephila clavipes dragline spider silk measured using the in situ rotation device.     

分光计循环扫描调节方法

分光计调节是学习和使用分光计的一大难点。通过分析指出分光计逐次逼近调节法只在部分条件下起作用,另外某些调节正好与目标方向相反;提出一种分光计循环扫描调节方法,按照一定的规律操作,可在短时间内调节成功,弥补了逐次逼进法的不足之处。     

A pulsed fourier spectrometer for impedance measurements of electrochemical systems

The facility is intended for measuring the impedance of electrochemical systems by the pulse method. The impedance spectrum is calculated by applying the Fourier transform to the step response (variation in the potential due to sample polarization by a step current pulse). The facility is controlled by a computer and contains a programmable galvanizer and 8-bit parallel ADC with a buffer RAM. Measurements are performed by the two-or three-electrode method over a frequency band of 10⁻³ to 3×10⁵ Hz with samples whose tan (δ) is within 0.01–100. The measurement error is 2%.     

In situ pressure measurements in dimpled elastohydrodynamic sliding contacts by Raman microspectroscopy

In situ pressure measurements within dimples formed in glass-steel point contacts under various sliding conditions were performed using Raman microspectroscopy. Experiments were conducted using a ball-on-disc type apparatus in which a circular contact is formed between a rotating glass disc and a rotating steel ball. Film thickness distributions were measured by duochromatic optical interferometry. Polyphenyl ether oil (5P4E) which has a high pressure-viscosity coefficient was used to produce a dimple in the contact area. Experimental results show that the pressure increases locally in the dimple zone and the pressure profile changes, accompanying the changes of the dimple location as a function of the slide-to-roll ratio. The maximum pressure is located downstream the maximum height of the dimple. The rheological response of the oil film under dimple occurrence conditions is discussed.     

便携式拉曼光谱仪的设计

研制了适合现场使用的便携式拉曼光谱仪。介绍了仪器的特点和组成、激光光源、拉曼光纤探头和CCD光纤光谱仪。     

Optical cell for combinatorial in situ Raman spectroscopic measurements of hydrogen storage materials at high pressures and temperatures

An optical cell is described for high-throughput backscattering Raman spectroscopic measurements of hydrogen storage materials at pressures up to 10 MPa and temperatures up to 823 K. High throughput is obtained by employing a 60 mm diameter × 9 mm thick sapphire window, with a corresponding 50 mm diameter unobstructed optical aperture. To reproducibly seal this relatively large window to the cell body at elevated temperatures and pressures, a gold o-ring is employed. The sample holder-to-window distance is adjustable, making this cell design compatible with optical measurement systems incorporating lenses of significantly different focal lengths, e.g., microscope objectives and single element lenses. For combinatorial investigations, up to 19 individual powder samples can be loaded into the optical cell at one time. This cell design is also compatible with thin-film samples. To demonstrate the capabilities of the cell, in situ measurements of the Ca(BH(4))(2) and nano-LiBH(4)-LiNH(2)-MgH(2) hydrogen storage systems at elevated temperatures and pressures are reported.     

An optical spectrometer for a confocal scanning laser microscope

An optical spectrometer for the visible range has been developed for the confocal scanning laser microscope (CSLM) Phoibos 1000. The spectrometer records information from a single point or a user-defined region within the microscope specimen. A prism disperses the spectral components of the recorded light over a linear CCD photodiode array with 256 elements. A regulated cooling unit cools the diode array, thereby reducing the detector dark current to a level, which allows integration times of up to 60 s. The spectral resolving power, λ/Δλ, ranges from 400 at λ = 375 nm to 100 at λ = 700 nm. Since the entrance aperture of the spectrometer has the same diameter as the detector aperture of the CSLM, the three-dimensional spatial resolution for spectrometer readings is equivalent to that of conventional confocal scanning, that is, down to 0.2 μm lateral and 0.8 μm axial resolution with an N.A.=1.3 objective.     

High throughput spectrometer for fast localized Doppler measurements

A new custom-built duo spectrometer has been commissioned for fast localized Doppler measurements of plasma ions in the Madison Symmetric Torus. The instrument combines very high optical throughput (transmission efficiency of 6% and etendue of 0.80 mm(2) sr divided into two simultaneous measurements) with good resolution (lambda/Deltalambda=5600). The design is a double grating variant of the Czerny-Turner layout and has been carefully optimized for fast (100 kHz) measurements of the C VI line at 343.4 nm. The instrument is currently being applied for high speed charge exchange recombination spectroscopy measurements.     

High accuracy wavelength calibration for a scanning visible spectrometer

Spectroscopic applications for plasma velocity measurements often require wavelength accuracies ≤0.2?A?. An automated calibration, which is stable over time and environmental conditions without the need to recalibrate after each grating movement, was developed for a scanning spectrometer to achieve high wavelength accuracy over the visible spectrum. This method fits all relevant spectrometer parameters using multiple calibration spectra. With a stepping-motor controlled sine drive, an accuracy of ～0.25?A? has been demonstrated. With the addition of a high resolution (0.075?arc sec) optical encoder on the grating stage, greater precision (～0.005?A?) is possible, allowing absolute velocity measurements within ～0.3?km/s. This level of precision requires monitoring of atmospheric temperature and pressure and of grating bulk temperature to correct for changes in the refractive index of air and the groove density, respectively.     

便携式拉曼光谱仪发展综述

拉曼光谱仪已经广泛应用于分析化学、安全检查、生物医学等领域,小型化、智能化是其发展的重要方面.便携式拉曼光谱仪具有体积小、检测方便等特点,便于现场测量与分析.目前,在药物检测、机场安检、爆炸物分析等领域便携式拉曼光谱仪受到青睐.对国内外产业化和实验室的便携式光谱仪的发展进行了比较全面的综述,最后对便携式拉曼光谱仪的发展...     

用于大气遥感探测的临边成像光谱仪

分析了大气临边成像光谱探测的原理,依据应用要求设计研制了光栅色散型紫外/可见临边成像光谱仪原理样机。该样机采用宽波段折射式消色差前置望远光学系统与改进的Czerny-Turner光谱成像系统匹配的结构形式,工作波段为540～800nm(一级光谱)和270～400nm(二级光谱),通过切换紫外、可见带通滤光片来实现两个波段分别探测,质量为8kg,体积为450mm×250mm×200mm。用该样机进行了实验室光谱实验,并对光谱分辨率进行了分析,测量了该样机的实际光谱分辨率。测量结果表明,该样机的实际光谱分辨率为1.3nm,接近其理论光谱分辨率1.12nm,满足设计指标1.4nm的要求,并具有体积小、质量轻等特点,适合空间遥感应用。     

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。     

Spectrally resolved thermoluminescence measurements in fluorescence spectrometer

Registration of thermoluminescence (TL) spectra technique for irradiated samples in Perkin Elmer LS 55 spectrometer using developed high-temperature accessory during single heating cycle is shown. Functionality of serial instrument for RT–773 K temperature range is significantly widen. Spectrally resolved TL dependencies for h-BN micropowders and bulk AlN single crystals following UV irradiation are studied. TL spectral features of h-BN powders, synthesized by carbamide and plasma-chemical techniques, are determined and quantified. It is shown that the difference between TL curves obtained by the described and the standard modes does not exceed 10%.     

A broadband and high throughput single-monochromator Raman spectrometer: application for single-wall carbon nanotubes

We present a high sensitivity single-monochromator Raman spectrometer which allows operation with a tunable laser source. The instrument is based on the modification of a commercial Raman spectrometer; such instruments operate with interference Rayleigh filters which also act as laser mirrors and are usually considered as inherently narrow band. In our design, the two tasks are separated and the filter can be freely rotated without much effect on the light alignment. Since rotation shifts the filter passband, this modification allows tunable operation with efficient stray light filtering down to 150 cm(-1). The design is optimized for single-wall carbon nanotubes, for which the performance is demonstrated using a tunable dye laser source. The spectrometer thus combines the high sensitivity with the broadband characteristics of usual triple monochromator systems.     

Electro-optical multichannel spectrometer for transient resonance Raman and absorption spectroscopy

An optical multichannel system is described, used for time-dependent absorption measurements in the gas phase and the liquid phase and for resonance Raman spectroscopy of short-lived transient species in the liquid phase in pulse radiolysis. It consists of either an image converter streak unit or an image intensifier coupled to a TV camera with computerized data handling. The system enables the recording of time-dependent absorption spectra or resonance Raman spectra of short-lived radicals and excited states with single electron and light pulses.     

星载差分吸收光谱仪摆镜控制系统设计

针对差分吸收光谱仪搭载于地球同步轨道卫星时对地成像的要求,设计了一种扫描摆镜转动控制系统。从摆镜控制结构设计、控制电路设计两个方面阐述了摆镜系统的方案。摆镜系统受载荷主控器控制,接收控制指令并回传当前摆镜位置状态,通过LMD18200驱动芯片进行功率输出,由步进电机和谐波减速器构成的驱动器驱动摆镜转动,编码器读取摆镜角度信息。给出了PWM(Pulse Width Modulation)波占空比的测定办法,并提出通过回转到成像起始点之前的方式,消除回程误差对成像区域步距不确定性的影响。实验结果表明该系统的步距角均值偏差小于1″,最大偏差小于5″,标准偏差小于2″。该光谱仪摆镜控制系统满足步距精度指标要求。     

A sample scanning system with nanometric accuracy for quantitative SPM measurements

A sample scanning device operating in a working volume of 30 x 30 x 18 microm with interferometer and capacitance-based controls of displacements, is described. The xy-stage uses plane mirror linear interferometers and fast phase-meters for control of displacements of precise ball-bearing stages driven by piezo flexure actuators. The stage operates with a full range bandwidth of 200 Hz, and an estimated accuracy (k = 2) of 3 nm + 1 x 10(-3) L, where L is the lateral displacement. A novel z-stage based on a kinematic coupling between two plates, the upper one being moved by three bimorph plates and the distance being measured by three capacitive sensor, is described. The tilt of the z-stage is kept within fractions of a microrad, leading to a full range estimated accuracy of 2 nm + 2 x 10(-3) h, where h is the vertical displacement. The control bandwidth is of about 1 kHz, thus allowing fast and accurate step-height measurements. In order to test the device used in a scanning probe microscope, micrometric patterned surfaces made using high resolution e-beam lithography and precise metal deposition on silicon are imaged. Results of pitch measurements are discussed and compared with those obtained using optical diffractometry.     

Electron spectrometer in adjustable triode configuration for photo-induced field emission measurements

We have constructed a new ultrahigh vacuum apparatus with a triode configuration for the systematic investigation of photo-induced field emission (PFE) from metallic or semiconducting cathodes. These are exposed to electric fields up to 400 MV∕m and laser irradiation by means of hole or mesh gates. Cathodes and gates are in situ exchangeable and adjustable with high precision to ensure a homogeneous extraction of electrons which are partially transmitted to the fixed electron spectrometer. Its hemispherical sector analyzer provides an energy resolution limit of 8 meV. The commissioning of the measurement system has been performed with a tungsten needle. Its temperature showed up in the high-energy tail of the electron spectrum, while its work function was derived from the spectral low-energy part combined with the integral current-voltage curve. First PFE measurements on B-doped Si-tip arrays yielded a small field emission current increase under green laser illumination. A shift and splitting of the energy spectra was observed which revealed different emission regimes as well as the photosensitivity of the cathode due to carrier excitation into the conduction band. For the full exploitation of the PFE system, a tunable laser over a wide eV-range is required.