A Study on the Optimum Design of the Condenser Lens of a Compact Electrostatic-Type SEM

A high resolution scanning transmission electron microscope of the type developed by A. V. Crewe is under construction in this laboratory. The basic design is completed and construction is under way with completion expected by the end of this year.The optical column of the microscope will consist of a field emission electron source, an accelerating lens, condenser lens, objective lens, diffraction lens, an energy dispersive spectrometer, and three electron detectors. For any accelerating voltage the condenser lens function to provide a parallel beam at the entrance of the objective lens. The diffraction lens is weak and its current will be controlled by the objective lens current to give an electron diffraction pattern size which is independent of small changes in the objective lens current made to achieve focus at the specimen. The objective lens demagnifies the image of the field emission source so that its Gaussian size is small compared to the aberration limit.

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A Newly Designed 650kv Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101268 ◽

1968 ◽

Vol 26 ◽

pp. 304-305

Author(s):

K. Shiraishi ◽

T. Katsuta ◽

S. Ozasa ◽

H. Todokoro

Keyword(s):

Electron Microscope ◽

High Voltage ◽

Bright Field Image ◽

Bright Field ◽

Push Button ◽

Condenser Lens ◽

High Voltage Generator ◽

Frequency Power ◽

Better Than ◽

Illuminating System

We have recently completed a newly designed 650KV electron microscope. An external view of this advanced instrument is shown in Figure 1. A symmetrical Cockcroft-Walton circuit has been adopted as the high voltage generator. The cathode is heated by high frequency power; a battery is not employed. The high voltage stability is better than 1 x 10-5/min.The sectional diagram of the column shown in Figure 2 is 420mm in diameter and 2750mm in height. The illuminating system consists of a double condenser lens and a magnetic alignment device. Dual deflector assemblies for dark and bright field images, selectable by push button, are built beneath the condenser lens. Two selectable stigmator power supplies are also provided for dark and bright field image operation.

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Optical characteristics of the hitachi HF-2000 cold field-emission TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151210 ◽

1993 ◽

Vol 51 ◽

pp. 1076-1077

Author(s):

L. F. Allard ◽

E. Völkl ◽

T. A. Nolan

Keyword(s):

Field Emission ◽

Recent Literature ◽

Electron Gun ◽

High Brightness ◽

Condenser Lens ◽

Illumination System ◽

High Resolution Images ◽

Imaging Mode ◽

Better Than ◽

Illuminating System

The illumination system of the cold field emission (CFE) Hitachi HF-2000 TEM operates with a single condenser lens in normal imaging mode, and with a second condenser lens excited to give the ultra-fine 1 nm probe for microanalysis. The electron gun provides a guaranteed high brightness of better than 7×l08 A/cm2/sr, more than twice the guaranteed brightness of Schottky emission guns. There have been several articles in the recent literature (e.g. refs.) which claim that the geometry of this illumination system yields a total current which is so low that when the beam is spread at low magnifications (say 10 kX), the operator must “keep his eyes glued to the binoculars” in order to see the image. It is also claimed that this illuminating system produces an isoplanatic patch (the area over which image character does not vary significantly) at high magnification which is so small that the instrument is ineffective for recording high resolution images.

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