100 KV Scanning Microscope

1972 ◽  
Vol 30 ◽  
pp. 472-473 ◽  
Author(s):  
A. V. Crewe ◽  
M. W. Retsky
Keyword(s):  
High Voltage ◽  
Voltage Divider ◽  
Electron Gun ◽  
Objective Lens ◽  
Parallel Beam ◽  
Emission Point ◽  
Error Amplifier ◽  
External Reference ◽  
Scanning Transmission ◽  
Transmission Microscope

A 100 kv scanning transmission microscope has been built. Briefly, the design is as follows: The electron gun consists of a field emission point and a 3 cm Butler gun. The beam has a crossover outside the gun and is collimated by a condenser lens.The parallel beam passes through a defining aperture and is focused by the objective lens onto the specimen. The elastic electrons are detected by two annular detectors, each subtending a different angle, and the unscattered and inelastic electrons are collected by a third detector. The spectrometer that will separate the inelastic and unscattered electrons has not yet been built.The lens current supplies are stable to within one part per million per hour and have been described elsewhere.The high voltage is also stable to 1 ppm/hr. It consists of the raw supply from a 100 kv Spellman power supply controlled by an external reference voltage, high voltage divider, and error amplifier.

A 100 KV Transmission Scanning Microscope

1971 ◽  
Vol 29 ◽  
pp. 22-23
Author(s):  
A. V. Crewe
Keyword(s):  
Focal Length ◽  
Electron Gun ◽  
Objective Lens ◽  
Scanning Microscope ◽  
Parallel Beam ◽  
Condenser Lens ◽  
Focal Length Lens ◽  
Short Focal Length ◽  
Pass Through ◽  
Correction System

A 100 kv transmission scanning microscope is now being constructed which should have a point resolution of 2.5 to 3 Å. The design of this microscope is similar to the design of our existing 30 kv 5 Å microscope, but there are several significant changes which are based upon some difficulties and sources of inflexibility of that microscope.A field emission electron gun of our usual design will be used as the source of electrons, the only difference being that the spacing between the anodes has been increased from 2 to 3 cm. The electron beam will then pass through a condenser lens which will produce a parallel beam of electrons. This parallel beam will then be focused onto the specimen by means of a short focal length lens (approximately 1 mm focal length). The reason for using a condenser lens to produce the parallel beam of electrons is that in the future a quadrupole-octupole correction system will be installed in this section of the microscope in order to attempt to correct the spherical aberrations of the objective lens and thereby improve its resolution.

Two Developments - A Superconducting Microscope Conversion and A Precision High Voltage Divider

1970 ◽  
Vol 28 ◽  
pp. 354-355
Author(s):  
R. E. Worsham ◽  
J. E. Mann ◽  
E. G. Richardson ◽  
N. F. Ziegler
Keyword(s):  
High Resolution ◽  
Liquid Helium ◽  
High Voltage ◽  
Experimental Evaluation ◽  
Voltage Divider ◽  
Bottom Plate ◽  
Objective Lens ◽  
Optical Bench ◽  
Radiation Shields ◽  
Helium Vapor

Two elements in the chain of development for a 500 kV high resolution microscope have been completed for initial experimental evaluation. They are a conversion of a Siemens Elmiskop I to use a superconducting objective lens and a 150 kV precisely regulated accelerating supply.The superconducting microscope, shown in Fig. 2 is designed as an optical bench for proving the cryostat, lenses, stage mechanism, and other parts prior to the design of a superconducting column for 500 keV. The lens as shown in Figs. 1 and 2 mounts on the removable bottom plate of the 7-liter helium vessel. The vessel is supported and can be clamped rigidly by the four sets of G-10 epoxy-glass posts. Radiation Shields I and II are concentric with the helium vessel. They are cooled by the boil-off helium vapor to about 30 and 130°K, respectively. All electrical leads are carried into the helium vessel through the four symmetrically located vents. Cooldowns from 77°K requires about 30 liters of liquid helium and the boil-off rate is 0.3-0.5 1/HR at either 4.2 or ∼ 1.8°K.

Some instrumental aspects of single atom microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 20-21
Author(s):  
D. Kopf ◽  
M. Utlaut ◽  
A.V. Crewe ◽  
M. Isaacson ◽  
W. Mankawich
Keyword(s):  
Surface Science ◽  
Science Studies ◽  
Scanning Transmission Electron Microscope ◽  
Electron Gun ◽  
Single Atom ◽  
Objective Lens ◽  
Heavy Atoms ◽  
Physical Experiments ◽  
Transmission Electron ◽  
Scanning Transmission

We have indicated in previous publications that a scanning transmission electron microscope (STEM) capable of atomic resolution may be a useful instrument for surface science studies and, in particular, capable of observing the distribution and diffusion of single heavy atoms on thin film substrates (1-3). In our previous work, we have used a microscope which was primarily oriented towards biological work and had a very simple optical system (only an electron gun plus an objective lens (4)). This limited the flexibility with which optical conditions would be changed. Moreover, the stringent requirements for atom imaging were not necessarily compatible for routine biological electron microscopy. Thus, we decided to shift our physical experiments in atom microscopy to another, more versatile instrument.This instrument is a modified version of a 100 keV STEM which has been described before (5). The basic system is indicated schematically in figure 1. It consists of a 3 cm Butler gun followed by a condensor lens, an objective lens and a projector lens (or in recent parlance, a “post specimen” lens).

Development of ultra high resolution analytical electron microscope ISI-EM-002A

1983 ◽  
Vol 41 ◽  
pp. 312-313 ◽  
Author(s):  
T. Yanaka ◽  
A. Yonezawa ◽  
K. Oosawa ◽  
T. Iwaki ◽  
S. Suzuki ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Voltage ◽  
Electron Gun ◽  
Objective Lens ◽  
Magnetic Circuits ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Mode 3 ◽  
High Voltage Generator

Total design concept of EM-002A is to realize the following essential performance, that is, 1) attainment to ultimate high resolution as the conventional electron microscope, 2) complete compatibility of the high resolution mode and the analytical mode, 3) identification of the analyzed region and the observed image with atomic-level resolution, 4) observation of ultra fine structure of the biological specimen with maximum high contrast and so on.[Electron source] Accelerating voltage ranges from 20kV to 120kV in 6 steps Double Cockroft-Walton circuit is used as the high voltage generator and the high frequency ripple voltage is reduced to 0.1V. Electron gun assembly is composed of high voltage alumina insulator, whose shape is so well designed as to suppress micro-discharge to the negligible order.[Objective lens and specimen chamber] The objective lens is a strong symmetrical lens where the specimen chamber is located between the symmetrical upper and lower objective lens magnetic circuits. The objective lens has two powerful pole pieces, one being used for the ultra high resolution mode and the other for the standard mode.

Electronic Cone Illumination with the Conventional Transmission Electron Microscope

1977 ◽  
Vol 35 ◽  
pp. 72-73
Author(s):  
William Krakow
Keyword(s):  
Electronic Device ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Hollow Cone ◽  
Transmission Electron ◽  
Lissajous Figures ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Diffraction Patterns ◽  
Transmission Microscope

An electronic device has been constructed which manipulates the primary beam in the conventional transmission microscope to illuminate a specimen under a variety of virtual condenser aperture conditions. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. The device has been utilized mainly for the hollow cone imaging mode where the device provides a microscope transfer function without zeros in all spatial directions and has produced high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens.

The Reduction of Chromatic Aberrations Due to Instrumental Instabilities

1971 ◽  
Vol 29 ◽  
pp. 14-15
Author(s):  
J. S. Lally ◽  
R. Evans
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Usual Practice ◽  
Voltage Electron ◽  
Short Focal Length ◽  
Chromatic Aberrations ◽  
Electron Microscopes

One of the instrumental factors often limiting the resolution of the electron microscope is image defocussing due to changes in accelerating voltage or objective lens current. This factor is particularly important in high voltage electron microscopes both because of the higher voltages and lens currents required but also because of the inherently longer focal lengths, i.e. 6 mm in contrast to 1.5-2.2 mm for modern short focal length objectives.The usual practice in commercial electron microscopes is to design separately stabilized accelerating voltage and lens supplies. In this case chromatic aberration in the image is caused by the random and independent fluctuations of both the high voltage and objective lens current.

Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM

1983 ◽  
Vol 41 ◽  
pp. 376-377
Author(s):  
Richard L. McConville
Keyword(s):  
Field Strength ◽  
Electron Probe ◽  
Spherical Aberration ◽  
Focal Length ◽  
Objective Lens ◽  
Parallel Beam ◽  
Tilt Axis ◽  
X Ray ◽  
Small Probe ◽  
Specimen Height

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.

SEM Examination of a Used Diamond Knife

1971 ◽  
Vol 29 ◽  
pp. 452-453
Author(s):  
J. Temple Black
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
High Magnification ◽  
Metallic Materials ◽  
Wide Spread ◽  
Thin Sections ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Scanning Electron ◽  
Diamond Knife

Since its introduction by Fernandez-Moran, the diamond knife has gained wide spread usage as a common material for cutting of thin sections of biological and metallic materials into thin films for examination in the transmission electron microscope. With the development of high voltage E.M. and scanning transmission E.M., microtomy applications will become increasingly important in the preparation of specimens. For those who can afford it, the diamond knife will thus continue to be an important tool to accomplish this effort until a cheaper but equally strong and sharp tool is found to replace the diamond, glass not withstanding.In Figs. 1 thru 3, a first attempt was made to examine the edge of a used (β=45°) diamond knife by means of the scanning electron microscope. Because diamond is conductive, first examination was tried without any coating of the diamond. However, the contamination at the edge caused severe charging during imaging. Next, a thin layer of carbon was deposited but charging was still extensive at high magnification - high voltage settings. Finally, the knife was given a light coating of gold-palladium which eliminated the charging and allowed high magnification micrographs to be made with reasonable resolution.

Description of a New High Resolution Scanning Transmission EM

1972 ◽  
Vol 30 ◽  
pp. 418-419
Author(s):  
Michael Beer ◽  
J. W. Wiggins ◽  
David Woodruff ◽  
Jon Zubin
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Energy Dispersive Spectrometer ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Condenser Lens ◽  
Transmission Electron ◽  
Pattern Size ◽  
Scanning Transmission ◽  
Under Construction

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.

In Situ Observation of Catalyzed Gasification of Graphite by Nickel

1981 ◽  
Vol 39 ◽  
pp. 76-77
Author(s):  
R. T. K. Baker ◽  
R. D. Sherwood
Keyword(s):  
Objective Lens ◽  
In Situ Observation ◽  
Gas Flows ◽  
Catalytic Gasification ◽  
Television Camera ◽  
Viewing Screen ◽  
Fuels And Chemicals ◽  
Gasification Of Carbon ◽  
Transmission Microscope

The catalytic gasification of carbon at high temperature by microscopic size metal particles is of fundamental importance to removal of coke deposits and conversion of refractory hydrocarbons into fuels and chemicals. The reaction of metal/carbon/gas systems can be observed by controlled atmosphere electron microscopy (CAEM) in an 100 KV conventional transmission microscope. In the JEOL gas reaction stage model AGl (Fig. 1) the specimen is positioned over a hole, 200μm diameter, in a platinum heater strip, and is interposed between two apertures, 75μm diameter. The control gas flows across the specimen and exits through these apertures into the specimen chamber. The gas is further confined by two apertures, one in the condenser and one in the objective lens pole pieces, and removed by an auxiliary vacuum pump. The reaction zone is <1 mm thick and is maintained at gas pressure up to 400 Torr and temperature up to 1300<C as measured by a Pt-Pt/Rh 13% thermocouple. Reaction events are observed and recorded on videotape by using a Philips phosphor-television camera located below a hole in the center of the viewing screen. The overall resolution is greater than 2.5 nm.

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