The relationship between transmission efficiencies in the FRR and fat modes of an electron spectrometer

The electron transmission efficiency as a function of kinetic energy for an electron spectrometer operating in the fixed analyser transmission (FAT) mode has been determined by direct comparison with the known transmission efficiency in the fixed retard ratio (FRR) mode. Results obtained from the background intensity and from the relative peak heights of a number of elements compare well with each other. They suggest that transmission in the FAT mode is nearly independent of kinetic energy.     

Intensity and energy calibration in AES: The effect of analyser modulation

To a large extent, Auger electron spectra (AES) are recorded and portrayed in the differential mode using the potential-modulation method with a phase-sensitive detector. The precise intensities of the peaks and their energy positions depend on the modulation amplitude in a nonlinear manner. This dependence, in turn, is also a function of the resolution and detailed construction of the analyser. Thus, accurate quantification and accurate assignments of peak energies depend on a detailed knowledge of the effect of analyser modulation in AES. The theoretical response of spectrometers to a Gaussian line is here analysed and compared with measurements for “singlet” peaks using several different commercial spectrometers. This shows that, in certain circumstances, the traditional methods of intensity and energy measurement can be transferred with accuracies as high as 3% and 0.05 eV, respectively. A method for calibrating the effective modulation amplitude, vital for accurate quantification, is presented in the following paper.     

Measurement of the transmission function of the hemispherical energy analyser of ADES 400 electron spectrometer

For determination of the transmission function of a hemispherical energy analyser of an ADES 400 photoelectron spectrometer (V. G. Sci.) a direct method is used. This method is based on the definition of the transmission coefficient of an energy analyser. The number of impinging electrons from an electron gun is measured by a Faraday cup and the current of passed electrons is determined as a peak area of the current signal from the channel multiplier which is used as the Faraday cup. The transmission function of the energy analyser of the ADES 400 photoelectron spectrometer is measured for four values of the analyser pass energy.Presented at the Seminar on Secondary Electrons in Electron Spectroscopy, Microscopy, and Microanalysis, Chlum (The Czech Republic), 21–24 September, 1993.     

Esca microscope — a new approach for imaging in XPS

This work demonstrates the feasibility of a novel yet simple method of obtaining XPS images using a conventional X-ray photoelectron spectrometer with a minimum of modification. A spherical sector electron energy analyser is operated in the selected area mode (small input aperture, moderate lens magnification) and deflection plates are introduced between the input lens and the sample, allowing the virtual image of the input aperture to be raster-scanned across the sample surface. The image is then formed by using the customary spectrometer output to z-modulate a synchronously raster-scanned video monitor. At present, the resolution is 150 μ but improvements to 10 μ should eventually be possible. Examples are given of studies on electronic components with insulating and conducting areas.     

The quantitative interpretation of peaks in photoelectron spectra obtained with dispersive electrostatic analysers

General expressions are obtained which show the relation between the height and area of a photoelectron peak and the partial photoionisation cross-section. It is shown that, if the height is used as a measure of intensity, the energy spread of the incident photon beam and the analyser bandpass must be considered. The importance of having a complete knowledge of the variation of analyser efficiency with electron energy is stressed, the cylindrical mirror analyser being given as an example.     

Graduation of electron spectrometer intensity scale. Part 1. A theoretical approach

We consider an ordinary spectrometer equipped with a dispersing field analyser (e.g. cylindrical mirror analyser (CMA)), an electron multiplier, and analogue differentiation facilities. Transformation of the true energy distribution of secondary electrons to the spectrometer output voltage is described mathematically using a spectrometer operator. Conditions are established that allow the mathematical expression of the operator to be reduced to a graduation function G(E′) of pass energy E′. The G(E′) function is defined as the product of a probability function definite integral and a multiplier gain coefficient. The operator and/or the graduation function take account of influences of any extraneous fields on the spectrometer output voltage.     

用于凝聚态物质研究的旋转晶体中子飞行时间谱仪

本文介绍了我所自行设计和制造的一台旋转晶体中子飞行时间谱仪。该仪器对凝聚态物质的各种动力学研究是一个有效的工具。我们通过选取适当的锗单晶(111)平面旋转轴的办法消除了仪器单色束中多晶面反射的“污染”(contamination)。该谱仪的入射初始中子能量范围可为10—100meV,对应的初始中子能量分辨率为2.5—7.2％。本文根据Brockhouse理论对散射中子的分辨率作了详细的理论计算,并将计算结果与实测结果进行了对比。介绍了标准钒样品的非弹性散射中子谱的测量结果并与国外几个同类型谱仪的基本特性作了比较。     

Effects of the working conditions of retarding field spectrometers on the energy distribution of secondary electrons

Retarding field spectrometers designed for Auger electron spectroscopy show spurious peaks in the low energy range which are connected with secondary electron emission from the electrodes of the spectrometer. We present a general explanation for all the spurious effects reported to date.The understanding of these phenomena has led us to the building of a new spectrometer which works with optimal experimental conditions.We present the results and experimental curves of secondary electron energy distribution for an evaporated aluminium target.     

Simultaneous energy analysis in a large angular range: A novel neutron spectrometer,its resolution and applications

A new type of crystal spectrometer for elastic and inelastic neutron scattering has been set up by modifying an existing flat-cone diffractormeter at the BER II-reactor in Berlin (West). The main difference to conventional triple axis spectrometers is the analyser part. It consists of large crystal plates which reflect the neutrons out of the horizontal plane into a curved multicounter. This allows simultaneous measurements in a large and continuous range of scattering angles for a constant energy transfer. The resolution function has been calculated and compared with experimental results. There is the possibility to focus acoustical phonons. We present applications together with experimental results such as quasielastic diffuse scattering in orientationally disordered crystals and inelastic scattering due to acoustical phonons. In combination with the flat-cone technique all elastic and inelastic scattering events of a single crystal can be collected in a systematic and efficient way.in collaboration with the Hahn-Meitner Institut, Berlin (West)     

Experimental determination of energy resolution and transmission characteristics of an electrostatic toroidal spectrometer adapted to a standard scanning electron microscope

The main characteristics of sectorial toroidal energy analyzer for a new electrostatic electron spectrometer adapted to a standard scanning electron microscope are defined and determined experimentally. These transfer characteristics, i.e. intensity-energy response and transmission functions, energy resolution and coupling constant, are needed for spectrometer calibration, registration and energy correction of measured backscattered electron spectra and microtomographic analysis of multilayered structures. The spectrometer response to a monoenergetic primary electron beam and to a continuous energy distribution is discussed. Detector response functions for energy independent and linear energy dependent detectors are considered. For aperture slits of the spectrometer which allow reasonable electron intensities at the detector an energy resolution of about 2.5% is obtained.     

A comparison of results of an ESCA study of nonconducting solids using spectrometers of different constructions

The binding energies of 17 photoelectron lines in the spectra of six chemical compounds have been measured using nine spectrometers of seven different types of construction. The results are treated statistically and the reasons for data variability analysed. The most reliable of these data, which would be suitable for checking the calibration of spectrometers, are indicated. For 13 lines of three compounds the relative intensities were measured and compared with theoretical data. It is shown that, provided the kinetic energies of the photoelectrons are sufficiently high, the results concerning relative intensities obtained using one instrument can be applied, with appropriate corrections, for quantitative analysis using other spectrometers, with an accuracy of ～10%. The spectral characteristics, intensities, contrasts and peak widths are compared for the different spectrometers and the need for further wide and objective comparisons of characteristics of serially manufactured instruments is pointed out.     

Angular- and spatial-dependent intensity behaviour for a prototype laterally inhomogeneous sample studied with an ES200B spectrometer

An investigation into the surface area sampled in an ESCA experiment for a laterally inhomogeneous sample is described. The experiments use a special sample with gold “islands” in a polymeric matrix machined to the normal dimensions as encountered when using an ES200B spectrometer. The spatial distribution of the X-rays is not symmetrical about the anode and the effective area of acceptance into the analyzer changes with the electron take-off angle.     

A low-volume cavity ring-down spectrometer for sample-limited applications

In atmospheric and environmental sciences, optical spectrometers are used for the measurements of greenhouse gas mole fractions and the isotopic composition of water vapor or greenhouse gases. The large sample cell volumes (tens of milliliters to several liters) in commercially available spectrometers constrain the usefulness of such instruments for applications that are limited in sample size and/or need to track fast variations in the sample stream. In an effort to make spectrometers more suitable for sample-limited applications, we developed a low-volume analyzer capable of measuring mole fractions of methane and carbon monoxide based on a commercial cavity ring-down spectrometer. The instrument has a small sample cell (9.6 ml) and can selectively be operated at a sample cell pressure of 140, 45, or 20 Torr (effective internal volume of 1.8, 0.57, and 0.25 ml). We present the new sample cell design and the flow path configuration, which are optimized for small sample sizes. To quantify the spectrometer’s usefulness for sample-limited applications, we determine the renewal rate of sample molecules within the low-volume spectrometer. Furthermore, we show that the performance of the low-volume spectrometer matches the performance of the standard commercial analyzers by investigating linearity, precision, and instrumental drift.     

An application of the electron mirror in the time-of-flight spectrometer

We suggest applying of the spherical electron mirror in the time-of-flight electron spectrometer with a position sensitive detector in order to increase the effective acceptance solid angle of the spectrometer. The spherical electron mirror is placed near the specimen and it focuses electrons on a position sensitive detector as a converging electron flux. The electron mirror increases the acceptance angle of the spectrometer by a factor of 20. The electron mirror of the spectrometer consists of an inner spherical electrode of the radius R and an outer spherical electrode of the radius 1.1R. The central segment of the inner electrode inside the linear angle of 80° is made of a grid. The detector plate radius is about 0.23R. The acceptance solid angle of the spectrometer with this electron mirror is about 1.1sr, the range of the polar angle of emission is 20°–90° relative to the surface normal, and the range of the azimuth angle of emission at its maximum is ±36° relative to the basic plane of the spectrometer. The design of the spectrometer allows to recover the electron trajectory for each detected electron and to calculate the energy and the emission angle of the electron. The energy resolution of the spectrometer is about 0.2 eV/ns for the electron energy of 10 eV. The energy range is from E_min0.1eU_r up to eU_r, where U_r is the retarding potential of the electron mirror. The perturbing influence of the grid of the electron mirror limits mainly the angular resolution of the spectrometer and affects relatively slightly the energy resolution. The electron spectrometer with two detectors and two electron mirrors symmetric about the spectrometer axis allows to measure electron pairs in coincidence in a wide range of emission angles and energies with k-resolutions.     

Monte Carlo Calculations of XRF Intensities in Annular Arrangements of Radioactive Source,Sample, Cylindrical Collimator and Detector

ABSTRACT

A Monte Carlo (MC) computer program for the calculation of the distribution of characteristic X-ray intensities as a function of the counting geometry is described. The program evaluates the contribution to the intensities of a fluorescent line from each point of the source, sample and detector. The main considerations of the calculation are based on the critical nature of the internal geometry of the main analyzer components within an energy dispersive X-ray fluorescence (EDXRF) spectrometer. The K XRF intensities for the inner and outer radius of the annular-sample and collimator radius were measured. An optimum geometry can be obtained by varying the collimator radius and the detector-sample distance. The results of the calculations show that the intensity distribution of the radioisotope excited fluorescent radiation through annular sample area is strongly dependent on the collimator radius, with a maximum intensity effect with a smaller sample area and with decreasing collimator radius. An investigation of the XRF intensities in the annular sample surface as a function of collimator radius is discussed.     

Multiple‐element spectrometer for non‐resonant inelastic X‐ray spectroscopy of electronic excitations

A multiple‐analyser‐crystal spectrometer for non‐resonant inelastic X‐ray scattering spectroscopy installed at beamline ID16 of the European Synchrotron Radiation Facility is presented. Nine analyser crystals with bending radii R = 1 m measure spectra for five different momentum transfer values simultaneously. Using a two‐dimensional detector, the spectra given by all analysers can be treated individually. The spectrometer is based on a Rowland circle design with fixed Bragg angles of about 88°. The energy resolution can be chosen between 30–2000 meV with typical incident‐photon energies of 6–13 keV. The spectrometer is optimized for studies of valence and core electron excitations resolving both energy and momentum transfer.     

Instrumental design and expected performance of coupled-moderator near-backscattering spectrometer at J-PARC

A near-backscattering (n-BS) crystal-analyzer neutron inelastic spectrometer, DIANA, has been proposed for construction at Japan Proton Accelerator Research Complex. It has originally been designed to view a decoupled non-poisoned moderator in order to obtain high intensity and good energy resolution. Recently, we have reconsidered the instrumental parameters including the type of moderator, by performing Monte-Carlo simulations in order to obtain better performance. Among four virtual n-BS spectrometers on different beam sources moderators, a coupled-moderator-source spectrometer has shown the best performance, i.e. compared to the original DIADA design between ninefold and fivefold enhanced intensities have been obtained with 21%-better to 35%-worse energy resolutions.     

Au表面等离子体激元激发的扫描探针电子能谱

结合扫描隧道显微镜（STM）与电子能谱仪是实现表面微区元素分析的途径之一．我们将环形电子能量分析器和三维扫描探针系统相结合,建立了一台扫描探针电子能谱仪(SPEES)．通过测量针尖近场发射束流激发的Au表面能量损失谱,我们用研究了Au原子的等离子体激元激发现象．进一步通过改变针尖－样品距离,我们研究了Au等离子体激元峰与弹性散射峰的强度比随针尖－样品距离变化的关系．研究结果发现该强度比与针尖－样品距离的关系并不是单调变化,而是在一个特定位置存在极大．     

Evaluation of full-field energy dispersive X-ray fluorescence imaging apparatus and super resolution analysis with compressed sensing technique

A full-field energy dispersive X-ray fluorescence (FF-EDXRF) imaging spectrometer that utilizes single-photon counting analysis with a charge-coupled device was developed in our laboratory. We evaluated the developed spectrometer with respect to its energy resolution, spatial resolution, quantitative performance, and elemental imaging and compared it with the corresponding characteristics of scanning-type EDXRF spectrometers. In addition, we demonstrate that the limit of detection and sensitivity deteriorate as the analytical area decreases. Finally, compressed sensing, which is a widely used information-processing technique, was applied for clearing XRF images.