Charged particle energy analyzer based on a modified cylindrical mirror in the ring-axis focusing mode

The electron-optical properties of systems with a modified structure of the energy analyzer in the form of a cylindrical mirror proposed earlier are investigated. The analyzer operating mode in which the source of charged particles is in the inner cylinder and the detector is on the cylinder axis (ring-axis focusing) is considered. It is shown using numerical simulation that the modified structure ensures higher focusing quality as compared to the traditional cylindrical mirror. The optimal structure and voltage supply are determined for which spherical aberration is five times smaller than with a conventional cylindrical mirror.     

Conical Mirror Energy-Analyzer

Electron optical properties of an axisymmetric mirror energy-analyzer are studied. The internal electrode represents a cylinder, and the external electrode is formed by two identical cones with common bases. It is shown that the relative aperture and resolution of such an analyzer are significantly greater than the corresponding parameters of a conventional cylindrical mirror. The internal electrode is made of three cylinders with different diameters, and the potentials of the cylinders are identical. Such a structure is used to further improve electron optical characteristics of the conical analyzer. At a relatively small beam angle, the resolution of the conical analyzer is two times greater than the resolution of the cylindrical mirror, and the difference of the resolutions amounts to an order of magnitude when the beam angle increases.

     

Photoelectron branching ratios with a cylindrical mirror energy analyzer

A cylindrical mirror photoelectron energy analyzer suitable for measuring photoelectron branching ratios is described. The analyzer incorporates a pre-retarding/ accelerating system. This configuration is shown to have advantages over a conventional mirror analyzer in reduced pressure-sensitive scattering effects which can effect the accuracy of the branching ratios, and in increased sensitivity to low energy electrons. The electron collecting efficiency of the analyzer for a number of operating modes is given.     

Improved cylindrical mirror energy analyzer

A study has been carried out of the electron-optical properties of improved design of the cylindrical mirror energy analyzer. Both external and internal electrodes of the analyzer are divided into three isolated parts, whereby the potentials on the individual parts can be regulated independently from each other. In symmetric operating mode at identical potentials on the side parts of the electrodes, a significant increase has been obtained in resolving power and light-gathering power of the analyzer compared to the standard design of the cylindrical mirror. In asymmetric operating mode, which is implemented in a linear potential distribution on the external electrode, the conditions have been found under which the linear dispersion of the analyzer increases several times.

     

Spherical analyzer with pre-retardation

The features of the spherical analyzer with and without pre-retardation are compared. The results are applicable to other types of spectrometers as, e.g., the cylindrical analyzer and the cylindrical mirror.     

Focusing properties of a mirror analyzer with hexapole cylindrical field

In this work, motion of charged particles is studied in a new-type electrostatic field—the multiple cylindrical one, formed by superposition of electrostatic fields of a cylindrical mirror and a circular hexapole. On a base of the power-series analytical technique of solution of the equation of motion presented in integro-differential form, charged particle trajectories are calculated. Data on focusing properties of hexapole cylindrical mirror analyzer are obtained.     

Sequential ISS-AES measurement with scanning auger microprobe

Continuous measurement of ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES) has been achieved in a single energy scan of a cylindrical mirror analyzer by introducing a floating high voltage power supply to the conventional AES system. This technique was applied for Au-Cu alloys to study the surface composition of the sputtered surface by ISS and AES sequentially. The result agrees well with the other works obtained by AES and by ISS separately.     

Cylindrical mirror energy analyzer with the input of charged particles through end-surface diaphragm

Computer simulation is used to study electron-optical properties of a cylindrical mirror analyzer with the input of charged particles through the end-surface diaphragm. Regimes with double crossing of the optical axis (two-stage analyzer) are considered to increase the linear dispersion. The external electrode of the electron-optical system under study can be divided into several insulated parts with independently controlled potentials. Such an approach allows the second-order tuning of focusing and wide-range variation in the dispersion. Optimal working regimes make it possible to increase the linear dispersion by a factor of 3–4 in comparison with the one-stage regime.     

Relativistic effects in the calibration of electrostatic electron analyzers. II. Parallel plate and cylindrical mirror analyzers

Relativistic correction terms up to the second order are derived for the kinetic energy of an electron travelling along the central trajectory, which crosses the non-relativistic foci of electrostatic parallel plate and cylindrical mirror analyzers. The effects of fringing fields and source geometry are neglected. In both cases the magnitude of relativistic corrections depends on the geometry of the analyzer, but generally it is smaller than for the toroidal family of analyzers.     

Orientation dependence of overlayer attenuation of electrons for the cylindrical mirror analyzer and a retarding field analyzer

The effect of a homogeneous flat overlayer in attenuating spectral lines is analyzed as a function of orientation for apertures corresponding to a 42.3° cylindrical mirror analyzer and 48° retarding field analyzer. Exponential attenuation with path length is assumed. Results are presented graphically for both isotropic and cosine distributions of sources. The numerical results are particularly useful when practical considerations require the use of an unsymmetrical sample orientation. The results are pertinent to measurements of inelastic mean free paths and are also related to the response of these spectrometers to different depth distributions of elements.     

Collecting efficiency of a cylindrical mirror electron energy analyzer with pre-retarding lens

The electron collecting efficiency of a cylindrical mirror energy analyzer incorporating retardation of the electrons prior to analysis has been determined over the range 0 to 30 eV by two methods. The first method requires the use of a vacuum ultraviolet monochromator to produce monoenergetic electrons of different energies; the second method involves measuring the energy-brightness relationship of the retarding optics and should be applicable to any deflection analyzer with pre-retarding optics. The results of the two methods are compared and the limitations of the latter method are discussed.     

Design of an Auger Electron Mössbauer Spectrometer (AEMS) using a modified cylindrical mirror analyzer

We have designed and built an Auger Electron Mössbauer Spectrometer (AEMS) for the detection of resonant ⁵⁷Fe Auger electrons using a modified commercial cylindrical mirror analyzer (CMA). The CMA final aperture was modified intentionally in order to increase electron transmission at the expense of reducing its energy resolution, from an original value of 0.5 % to a value of 11 % after the modification. The Channeltron detector electronics and the pre-amplifier were also modified in order to increase the counting efficiency. The electron energy analyzer is selective in energy in the 30 eV–3000 eV range, so the spectrometer can be used to detect MNN (45 eV) and LMM (600–700 eV) Fe Auger signals, what gives it a high surface sensitivity for Fe containing samples. We have used it to acquire the Fe LMM Auger signals generated from the de-excitation process after γ-Ray resonant nuclear absorption. The spectrometer can be used to study samples non-enriched in ⁵⁷Fe, with acquisition times from 5 to 7 days, what is a big advantage. From electron trajectory Monte Carlo simulations in metallic iron, the mean-escape-depth of the detected Auger signals has been estimated in approximately 1 nm. Fe K conversion electrons and KLL Auger electrons with mean escape depths of 129 nm and 78 nm respectively also contribute to the detected signal although in a lesser proportion.     

A new electron spectrometer design:II

A novel charged particle energy analyzer of simple geometry is described. Expressions for the potential distribution and electric field components defined by the geometry are given. A raytrace program using these components is discussed and results of its application are presented in graphical and tabular form. Also presented are experimental results for two versions of the analyzer in the form of representative spectra of well known species (Ar⁺, H₂⁺, O₂⁺). Finally, a comparison of the new instrument with the well known cylindrical mirror analyzer is outlined which suggests the superiority of the new instrument under the specific conditions given.     

Development of a miniature double-pass cylindrical mirror electron energy analyzer (DPCMA), and its application to Auger photoelectron coincidence spectroscopy (APECS)

We have developed a miniature double-pass cylindrical mirror electron energy analyzer (DPCMA) with an outer diameter of 26 mm. The DPCMA consists of a shield for the electric field, inner and outer cylinders, two pinholes with a diameter of 2.0 mm, and an electron multiplier. By assembling the DPCMA in a coaxially symmetric mirror electron energy analyzer (ASMA) coaxially and confocally we developed an analyzer for Auger photoelectron coincidence spectroscopy (APECS). The performance was estimated by measuring the Si-LVV-Auger Si-1s-photoelectron coincidence spectra of clean Si(1 1 1). The electron-energy resolution of the DPCMA was estimated to be E/ΔE = 20. This value is better than that of the miniature single-pass CMA (E/ΔE = 12) that was used in the previous APECS analyzer.     

A design for a cylindrical mirror analyser for use in auger spectroscopy

The design of a cylindrical mirror analyser for use in Auger spectroscopy is discussed. The main feature of the design is the use of hemicylinders in place of the usual full cylinders. Although there is a consequent loss in solid angle of collection the loss is offset by a relaxation in machining tolerances, greater access to the specimen, and a simpler method of construction. An analyser built to this design has been operated and found to have a resolution of 0.35% for a semiangular aperture of ± 6°. The limitation on resolution appears to be set by the size of the incident electron beam on the target.Auger and loss spectra obtained with the analyser are shown and compared with those for the same material obtained with a conventional retarding-field analyser.     

A tunable bragg cavity for an efficient millimeter FEL driven by electrostatic accelerators

A comparison between three possible cavity configurations, the confocal cavity, the ring cavity and the Bragg cavity is presented for a millimeter FEL set within the high voltage head of an electrostatic accelerator. A simple mechnical design to make the Bragg cavity tunable is proposed. The usual theory of the sinusoidal Bragg corrugation, in cylindrical geometry, is extended to the rectangular corrugation and, further, the theory of the Bragg mirror is extended to rectangular geometry. The features of a Bragg mirror in cylindrical and rectangular geometry are compared.     

Collimating Montel mirror as part of a multi‐crystal analyzer system for resonant inelastic X‐ray scattering

Advances in resonant inelastic X‐ray scattering (RIXS) have come in lockstep with improvements in energy resolution. Currently, the best energy resolution at the Ir L₃‐edge stands at ～25 meV, which is achieved using a diced Si(844) spherical crystal analyzer. However, spherical analyzers are limited by their intrinsic reflection width. A novel analyzer system using multiple flat crystals provides a promising way to overcome this limitation. For the present design, an energy resolution at or below 10 meV was selected. Recognizing that the angular acceptance of flat crystals is severely limited, a collimating element is essential to achieve the necessary solid‐angle acceptance. For this purpose, a laterally graded, parabolic, multilayer Montel mirror was designed for use at the Ir L₃‐absorption edge. It provides an acceptance larger than 10 mrad, collimating the reflected X‐ray beam to smaller than 100 µrad, in both vertical and horizontal directions. The performance of this mirror was studied at beamline 27‐ID at the Advanced Photon Source. X‐rays from a diamond (111) monochromator illuminated a scattering source of diameter 5 µm, generating an incident beam on the mirror with a well determined divergence of 40 mrad. A flat Si(111) crystal after the mirror served as the divergence analyzer. From X‐ray measurements, ray‐tracing simulations and optical metrology results, it was established that the Montel mirror satisfied the specifications of angular acceptance and collimation quality necessary for a high‐resolution RIXS multi‐crystal analyzer system.     

Construction of an electron analyzer with a wide acceptance solid angle

We have developed a new electron energy analyzer with a large solid angle of 0.14π, which is comparable to that of cylindrical mirror analyzer. Typical energy resolution was ΔE/E₀ ∼ 0.016 for the aperture of 1 mm and central radius of 100 mm, and typical angular resolution was less than 0.5°.     

Path distribution of emission electrons with small energy losses in solids

An algorithm for the calculation of both the electron elastic reflectivity and the electron path distribution in a substance is proposed. In the approximation of quasi-elastic electron scattering the energy-loss spectra in the vicinity of the elastic reflection peak, as well as near the Auger and photoelectron lines are considered. For the geometry of a cylindrical mirror analyzer the differential coefficients of 2 keV electrons elastically reflected from the surfaces of 26 elementary substances (4 Z 82) have been studied. The numerical calculations and the experimental data are compared. Formulae useful for processing emission spectra are derived.     

Vacuum ultraviolet resonance line radiation source from rare gas atoms and ions for UHV photoelectron spectroscopy

A source and differential pumping system for producing high intensity resonance line radiation from rare gas atoms and ions for ultrahigh vacuum (UHV) photoelectron spectroscopy has been developed. Photoelectron count rates from a gold sample, as measured with a double-pass cylindrical mirror analyzer at pass energy 15 eV and 0.10 eV resolution, are ～ 300,000 c s^?1 for the He(I) (21.22 eV) line and ～30000 c s^?1 for the He(II) (40.81 eV) line. The source design is based on the principle of the electrostatic charged particle oscillator and is capable of sustaining discharges over the pressure range 1 to ～ 10^?6 torr. The discharge segment consists of a cylindrical cold cathode surrounding two tungsten rod anodes which are held at high positive potential. Three stages of differential pumping are employed in order that the vacuum in the main spectrometer chamber can be maintained at 2 × 10^?10 torr during operation. The calculated helium flow reaching the main chamber under these conditions is < 101 s^?1. Details of the construction and operating characteristics of the source are presented.