Electrostatic Electron Energy Analyzer Research Articles

Using electrostatic energy analyzer of a plane of symmetry for recording field emission spectra from carbon nanotube array

In this paper, the possibility is discussed of using electron emission spectroscopy to study low voltage field emission phenomenon. While using an electrostatic electron energy analyzer with the plane of symmetry, electron energy spectra were recorded with the energy resolution of ΔE ≈ 10-30 meV. The energy analysis has been done of the electrons emitted from the array of nanotubes produced by CVD method. The conclusion is that the low-voltage emission is local and that it is caused by very strong and inhomogeneous electron field produced by surface charged defects.

Element-resolved Kikuchi pattern measurements of non-centrosymmetric materials

Angle-resolved electron Rutherford backscattering (ERBS) measurements using an electrostatic electron energy analyser can provide unique access to element-resolved crystallographic information. We present Kikuchi pattern measurements of the non-centrosymmetric crystal GaP, separately resolving the contributions of electrons backscattered from Ga and P. In comparison to element-integrated measurements like in the method of electron backscatter diffraction (EBSD), the effect of the absence of a proper 4-fold rotation axis in the point group of GaP can be sensed with a much higher visibility via the element-resolved Ga to P intensity ratio. These element-resolved measurements make it possible to experimentally attribute the previously observed point-group dependent effect in element-integrated EBSD measurements to the larger contribution of electrons scattered from Ga compared to P.

Two-electrode charged particle energy analyzer with a quasi-linear electrostatic field

A simple design of an electrostatic secondary electron energy analyzer suggested by the author is studied theoretically. The analyzer consists of two, planar and dihedral, electrodes. A formula for the potential distribution in this device is derived. The parameters of the analyzer operating as a spectrometer and a spectrograph are numerically calculated. The device is intended for determining the surface composition of the sample irradiated by primary electrons or X rays.

Krypton fine structure in perpendicular-plane electron-impact ionization

The dynamics of the outgoing electrons, from the separated fine-structure ionic states of the $4p$ valence shell of krypton atoms, are observed for the single ionization process by incident electrons with energies from 5 to 50 eV above threshold. Triple differential $(e,2e)$ ionization cross sections are deduced from observations made in the ``perpendicular-plane'' scattering geometry using the same toroidal electrostatic electron energy analyzer for both outgoing electrons. For equal energy outgoing electrons, single and double scattering mechanisms account for the major characteristics of the cross sections. The double scattering becoming increasingly dominant as the excess energy increases; the behavior otherwise is very different from helium.

High-resolution energy analyzer with a large angular acceptance for photoelectron spectromicroscopy applications

A new design of an electrostatic electron energy analyzer is presented, that is characterized by a high energy resolution and a high efficiency of collection of photoelectrons originating from submicron areas. The analyzer uses an original low-aberration electrostatic mirror for collecting electrons, followed by a retarding hollow cylindrical lens and a hemispherical energy analyzer. Feasible modifications of the analyzer are discussed.

New type of high-resolution high-transmission energy analyzers based on toroidal mirrors

Abstract A new mirror-type axially-symmetric electrostatic electron energy analyzer is proposed, in which the outer electrode is toroidal. The toroidal geometry provides for remarkably good focusing properties of the analyzer, and thus allows to achieve a high angular acceptance at a high energy resolution. The same properties are found in the analyzers where the shape of the outer electrode is approximated by simple cylindrical and conical surfaces. Different modes of operation of the toroidal mirror analyzer are investigated, including its usage as a part of a multistage device.

Scanning photoelectron microscope with a laser-produced plasma X-ray source

Abstract We are developing a photoelectron microscope on a laboratory scale by using a laser-produced plasma X-ray source. It consists of a laser-produced plasma X-ray source, a monochromator with a toroidal mirror and a concave grating, a grazing incidence focusing mirror (Wolter type-I) and a hemispherical electrostatic electron energy analyzer. In this study, we intend to measure photoelectron spectrum images. The X-ray beam spot size was 9 μm×13 μm. An Au evaporated microchannel plate (MCP) was used as a sample.

Measurement of superthermal electron flow and temperature in a reversed-field pinch experiment by an electrostatic electron energy analyser

An electrostatic electron energy analyser has been inserted for the first time in the outer region of the RFX reversed-field pinch experiment, in order to investigate and characterize the presence of a superthermal electron population. It has been found that these electrons carry most of the current density parallel to the magnetic field. The time evolution during a single discharge of the superthermal electrons current density and parallel temperature indicates that the distortion of the electron distribution function is stationary during the plasma current flat-top phase. The dependence of the superthermal temperature on the plasma parameters has been investigated by varying the plasma density, and a relationship with the ratio of the on-axis applied electric field to the critical electric field for runaway generation has been identified.

SIMION study of the fringing field effects in deflector-type electrostatic electron energy analyzers: A new flexible Jost-based correction scheme

The common use of physical stops (such as slits and apertures) at the entrance and exit planes of a deflector-type electrostatic electron energy analyzer often introduces unwanted distortions in the ‘‘ideal’’ equipotential distribution and reduces the deflection angle. Since Herzog’s classic work on the fringing field correction, a variety of correction schemes have been devised. Most of these correction methods are not entirely satisfactory particularly for applications that require the use of position sensitive detectors (PSDs). In the present work, we investigate the effects of physical stops and Jost plates on the fringing field in a standard hemispherical energy analyzer by using the electron ray-tracing simulation program SIMION. By balancing the fringing field effect due to the physical stops with that of the Jost plates, we extend the correction scheme proposed earlier by Jost. The present correction scheme has the advantages of ease of construction and compatibility with PSDs.

Magnetic fluctuation induced transport in MST (abstract)a)

We made local measurements of the magnetic fluctuation induced transport of particles and energy in the outer region (r/a≳0.75) of the MST reversed field pinch plasma. These measurements allow comparison with the Rochester–Rosenbluth stochastic diffusion coefficients. An electrostatic electron energy analyzer and fast pyrobolometer were employed in combination with magnetic pickup coils to directly measure the correlated products 〈J̃θB̃r〉 and 〈q̃∥B̃r〉, respectively. Magnetic fluctuation induced transport of both particles and energy is negligible at the extreme edge of MST (r/a≳0.9), but increases to a level consistent with estimates of the entire particle and energy flux as the core is approached (5×1021 m−2 s−1 and 105 W m−2). Stochastic particle transport is limited by an apparent ambipolar electric field to the ion stochastic diffusion rate (D=50 m2 s−1), the electron transport being dominated by the energetic component of the distribution (E≳50 eV). The measured heat transport is consistent with the convective energy transport carried by the fast electron component (Teffective=100 eV).

Novel toroidal electrostatic electron energy analyser

The characteristics of a novel, double toroidal, electrostatic electron energy analyser, with input and output optics, have been established. The energy and angular dispersed image on the surface of a microchannel plate detector enables parallel data processing and significant gains in efficiency. The characteristics of the toroids and lenses, including time dispersion, have been modelled using standard relaxation techniques and are compared with measured values. The calculations predict hemispherical radial magnification and second order focusing with 0.7% accuracy. The differences between point and distributed object sizes, such as may occur with solid and gas targets, are indicated. Measured elastic differential cross sections for 50 eV electrons scattered from argon and an Auger spectrum from argon are in good agreement with modelled data

Electron spin detector for spin-resolved x-ray photoelectron spectroscopy

A low-energy diffuse scattering electron spin detector for spin-resolved x-ray photoelectron spectroscopy (SRXPS) is described. The detector is coupled to a commercial 152-mm mean radius, 150° spherical sector electrostatic electron energy analyzer. Electron optics are described for both the transport of photoelectrons from the energy analyzer exit slit to the gold scattering target, and from the gold target to the spin analyzer electron detectors. The spin detector has an effective Sherman function of 0.078±0.008, with a figure of merit of approximately 4×10−5. The electron optical phase space acceptance EAΩ of the detector is 623 eV mm2 sr. The SRXPS apparatus performance is demonstrated with SRXPS spectra from ferromagnetic Fe and a cobalt-based ferromagnetic glass.

Rotational state distributions from vibrational autoionization of H2 revisited

Photoelectron spectra of vibrationally autoionized (X 2Σ+g)np, v=1,2 Rydberg states of H2 were obtained by using an optical–optical double-resonance technique. The spectra were obtained by using a hemispherical electrostatic electron energy analyzer that had sufficient resolution to determine the rotational state distributions of the H+2 ions. The ionization process occurred in a magnetic and electric field-free region. All of the results are consistent with the assumptions that the photoelectrons are ejected as p waves and that spin effects are negligible. This is in sharp contrast to our earlier results obtained by using a magnetic bottle electron spectrometer, in which the ionization process occurred in a 0.5–1.0 T magnetic field [J. L. Dehmer et al., J. Chem. Phys. 90, 6243 (1989)]. It is concluded that the magnetic field can significantly modify the rotational distributions observed for vibrational autoionization. The implications of this conclusion are discussed, with particular attention to other experiments performed with the magnetic bottle spectrometer.

A two-dimensional data-acquisition system for a display-type electron energy analyser

A parallel-detection digital data-acquisition system for an ellipsoidal-mirror display-type analyser (EMDA) is described. The operation characteristics for its use in photoelectron spectroscopy are presented. The system is based on an optical readout of the two-dimensional angular intensity distribution of photoelectrons with a phosphor screen of a microchannel plate and a precision SIT video camera. A real-time image-processing system is used for digital video-data processing. Angular distribution patterns of photoelectrons can be obtained in a time of 4-10 s. Energy distribution spectra are recorded in a parallel-detection mode within the whole acceptance cone (88 degrees ) of the EMDA more than two orders of magnitude faster than with a conventional zero-dimensional electrostatic electron energy analyser. The different modes of operation of the EMDA and their realisation with the data-acquisition system are described.

X-ray and Auger transitions in highly ionised argon recoil ions

Argon recoil ions were produced by heavy-ion collisions and the argon K X-rays and Auger electrons emitted were measured with a crystal spectrometer and an electrostatic electron-energy analyser. Ions of Kr, Xr, Pb and U of 2.5-9.0 MeV amu-1 specific energy were used to bombard argon gas. This is the first systematic study of resolved K X-ray radiation and for K-Auger electrons of argon where the nuclear charge of the projectiles is larger than the nuclear charge of the target atoms (Z1>Z2). In these collision systems one-, two-, and three-electron spectra are observed which have been analysed in detail. From the kinematic broadening of Auger electron lines of Ar15+ the authors deduce a mean recoil energy of ER=21+or-3 eV. A drastic charge state effect as well as the systematics in the K alpha satellites for primary charges 26<or=q1<or=66 lead to a universal scaling of the L-hole probability pL as a function of projectile charge and velocity.

Compact analyzer and goniometer for angle-resolved electron spectroscopy

We discuss the design and construction of a modified electrostatic plane mirror electron energy analyzer mounted on a novel dual axis goniometer. The system is compact, bakable, and well suited for ultrahigh vacuum angle-resolved photoelectron spectroscopy. The device is relatively inexpensive and simple to construct, yet provides ample performance and versatility. In particular, preaccelerating electron optics have been developed which allow operation of the analyzer in the constant pass energy mode with uniform sensitivity over an increased energy range. A differentially driven goniometer allows the polar and azimuthal directions of detection to be varied independently and read directly. Test results are presented and angular and energy resolutions of 3° and 3% are reported.

Photoelectron energy analysis in a strong magnetic field: The role of elastic scattering

A new photoelectron spectroscopic method is described directed towards the measurement of the photoelectron spectra of trapped ions. An electrostatic retarding field electron energy analyser incorporating a channel plate is included with an ion trap in a strong magnetic field. The form of photoelectron spectrum is shown to be strongly influenced by a elastic scattering effects which can be enhanced by using an electron trapping potential well. The resultant spectra then have a particularly simple and useful form.

The use of fourier transforms for isolating components of experimental data

Fourier transform techniques were used to analyse a time series of experimental data in order to isolate a repeatedly scanned component, periodic and non-periodic temporal components and noise. The method was applied to a rocket-home electrostatic electron energy analyser being swept at a fixed rate, but having the spectra modified by non-periodic temporal variations and modulation at the spin rate of the rocket. It was found that by suitable displacement of the data amplitude origin and shaping of the ends of the time series, a very good separation of the various components was obtained. This indicates that the technique is a method particularly applicable to analysing data in which different periodic components are present.

Variable angle photoelectron spectrometer

The design, construction, and performance of a spectrometer for measuring the angular and energy distributions of electrons photoejected by rare gas resonance light is described. Results using 584.4-Å photons from a helium lamp are reported. Flexibility of instrumental design allows for the use of other light sources. A 180° hemispherical electrostatic electron energy analyzer is rotatable about the center of an enclosed sample chamber. The instrument is highly automated, with an on-line computer used to control the detector angle and the data acquisition and reduction. This automation is required by the long and continuous data acquisition.

High time resolution electrostatic electron analyzer

A gridded electrostatic electron energy analyzer is described which has been used successfully to time resolve trapped electron distributions at 200 MHz in a beam plasma device. Examples of raw data and extracted phase space plots are presented.