Spherical aberration correction of electrostatic lenses using spherical meshes
01 Jul 1995-Journal of Vacuum Science and Technology (American Vacuum Society)-Vol. 13, Iss: 4, pp 2255-2260
TL;DR: In this paper, the spherical aberration of electrostatic lenses can be corrected for the aperture angle of up to 60° by introducing spherical meshes, based on the capability of stigmatic imaging by a spherical refractive surface in light optics.
Abstract: The spherical aberration of electrostatic lenses can be corrected for the aperture angle of up to 60° by introducing spherical meshes. The principle of correction is based on the capability of stigmatic imaging by a spherical refractive surface in light optics. The electrostatic potential distribution around a mesh required for the correction was studied using the analytical expression of the general solution of the Laplace equation, and the amount of aberration was determined by ray tracing. It is shown that the sign of spherical aberration at a virtual image produced by the field near the mesh can be made positive or negative, according to the position of the object and the degree of deformation of the electrostatic field from spherical symmetry when retreating from the mesh surface. It thus becomes possible to cancel the spherical aberration of a focusing field which follows the field near the mesh, and a total lens field without spherical aberration is realized. The possibility of canceling the spherical aberration is verified in a practical design example of an extraction lens for electron spectrometers, which may increase the sensitivity to much higher than that obtained with conventional lenses.
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21 Mar 2009-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the authors consider the possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data, and the properties of a recently developed angle-resolving TOF system (AR-TOF) are discussed.
Abstract: The demand for simultaneous observation of photo-electron distributions in several dimensions has made the hemispherical deflection analyzer (HDA) and the time-of-flight (TOF) analyzer the dominating spectrometer types. Some common limiting factors for resolution and sensitivity are considered. Recent developments of the HDA and its lens system which increase the energy range and angular acceptance are described. The properties of a recently developed angle-resolving TOF system (AR-TOF) are also described. The possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data is discussed.
53 citations
Patent•
10 Feb 2011
TL;DR: In this paper, an aberration corrector is used to correct the electron beam for at least a spherical aberration in the path of an electron beam in a transmission electron microscope.
Abstract: A transmission electron microscope includes an electron beam source (20) to generate an electron beam Beam optics are provided to converge the electron beam An aberration corrector (90) corrects the electron beam for at least a spherical aberration A specimen holder is provided to hold a specimen (40) in the path of the electron beam A detector (80) is used to detect the electron beam transmitted through the specimen The transmission electron microscope operates in a dark- field mode in which a zero beam of the electron beam is not detected The microscope may also be capable of operating in an incoherent illumination mode
46 citations
TL;DR: In this paper, a display-type ellipsoidal mesh analyzer (DELMA) has been developed to overcome the difficulties faced in the display-based spherical-mirror analyzer having been used so far.
24 citations
Patent•
07 Jun 2011
TL;DR: In this paper, an aberration corrector corrects the electron beam for at least a spherical aberration and a specimen holder is provided to hold a specimen in the path of the beam.
Abstract: A transmission electron microscope includes an electron beam source to generate an electron beam. Beam optics are provided to converge the electron beam. An aberration corrector corrects the electron beam for at least a spherical aberration. A specimen holder is provided to hold a specimen in the path of the electron beam. A detector is used to detect the electron beam transmitted through the specimen. The transmission electron microscope may operate in an incoherent mode and may be used to locate a sequence of objects on a molecule.
23 citations
TL;DR: The present paper creates the possibility for beam analysis by achieving dramatic improvements in deceleration lens capabilities, which provides a scheme for simultaneous angular distribution measurement suitable for application to high-energy charged-particle beams up to around 10 keV.
Abstract: Recently, it was shown that using an ellipsoidal mesh in an einzel-type lens, spherical aberration can be corrected over a wide acceptance angle of up to 120\ifmmode^\circ\else\textdegree\fi{}. The present paper creates the possibility for beam analysis by achieving dramatic improvements in deceleration lens capabilities. This provides a scheme for simultaneous angular distribution measurement suitable for application to high-energy charged-particle beams up to around $10\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. We consider the behavior of wide-angle charged-particle beams in electrostatic fields given by simple solutions of the Laplace equation, starting with a discussion on a spherically symmetric deceleration field. A beam focusing over a wide acceptance angle of 100\ifmmode^\circ\else\textdegree\fi{} is found in a special spherically symmetric field. However, in many cases of the spherically symmetric field, focusing of wide-angle beams is obstructed by the presence of spherical aberration. We show that the spherical aberration can be corrected by two kinds of deformation of the spherically symmetric field, a deformation of the field under a spherical boundary condition and an ellipsoidal deformation of the field. We study practical realization of such fields under the use of a few electrodes and a curved mesh (spherical or ellipsoidal mesh). Some variations of the arrangement of electrodes are considered, and simple designs of deceleration lenses with wide acceptance angles of up to 120\ifmmode^\circ\else\textdegree\fi{} are obtained. Here fine focusing of wide-angle beams can be achieved in a three-electrode deceleration lens with an ellipsoidal mesh.
22 citations